More Franzy

Its a long holiday weekend ahead and I'm so happy playing in my little sanctuary.

Is for my bench drill & bench belt grinder, 5ft long 2 ft wide. Completely out of 15mm sheet plywood.

Its lightweight but extremely rigid.

Why? Because I can

Free plan is available upon request.

(As I don't know how to host one for download.... :(  but if someone could teach me... )

The bench in commission...
I has envisage a much tidy & organised working area... but I don't quite get that result... This call for more furniture???

Dust Making Franzy

With a newly constructed sturdy as a rock 8 ft long workbench, there is no way I'll rest my tools... Anyway, I "do" really need some storage & shelving in my little sanctuary, Any excuse is better then non... I'll started with a book case.

Its soooooooo comfortable.... NO BACK ACHE,

Hmm.... doesn't feel right, I think 4 feet spend is too far for the shelves... & a bit too wobbly as well

Have no fear, help is always is at hand. Nothing a 15x45mm wood to reinforce the shelves & more plywood as shear reinforcement in the cavity.

Here we are... Do I need finishing as she will always be in the store room under the stairs.

............... maybe a coat of shellac later.... aaaaa....loooot.... laaaaterrr....

What next... another bench for my drilling machine & bench sander????

Workbench

Got tired of using makeshift table & boxes...

Now that I have an empty shop to tinker, I must build a custom workbench.

Free plan of the bench is available upon request.

 .

The stuff that makes up a PSU

In the previous post, I choose a E-I Core, 300VA, Secondary winding 48Vac. which should have 66.5Vdc 4.5A

I happened to have a 540VA, Double bobbin, 36Vac E-I core tranny collecting dust in my junk box. It says 36V, 15A, So I approach a friend to add a few more coils on the secondary and I now I have a 48Vac, 11.25A tranny for the job.











Now for the Capacitor,

Voltage rating,
It is safe to have a 1.5x safety factor over the expected rated peak,
So, 66.5 x 1.5 = 99.75V
so a 100V rating Cap will do just fine.

Another safe formular to guide us along,
C = (80,000 * IMax. total) / Vdc (microFarad)
C= 80,000*(4*4)/66.5 = 19,248.12 uF

Capacitors don't come in this exact size
This is what I found off the shelve, a 22,000uf, 100Vdc Screw terminal electrolytic capacitor.




Ractifier is easy,
minimum Voltage rating is 100V, minimum current rating is 4x4x1.5=24Amp but we know from the tranny selection 2/3 of that would be enough so 2/3 of 24 is 16Amp

I got this KBPS2504,250V & 25A. metal casing which is good for heat dissipation. when I mount it to any metal plate.

Next, is Wire selection, We know the motor rating is 4A max, but nominal operating current will be much less. Anyway,  14 gauge AWG wires will do 4amp nicely & since they are easy to get I used some 8Awg (easily 15Amp) speaker cables for the job. all I need now is some crimping pins, some soldering work....


A quick wiring work yielded this

Value Engineering the Stepper Motor PSU

The word "DESIGN" had been over rated & over used... Everyone in the advertisement design something... I prefer to use "SELECTION".  e.g. select a few different color clothing & you have a in-store fashion designer... do you "design" a 200hp engine for your car or you select? Do you select chopstick over fork & Knife or design... Can anyone claim the credit of designing a wheel? but we keep seeing this " we design of the wheel to xxxx, yyyy......."

Enough of my ranting, lets get back to the Stepper motor Selection.

Like everything else, we must know what we need before we can conduct a proper selection.

Stepper motor system consist of a stepper motor and a Stepper motor driver or amplifier.

Stepper motors takes in high current pulses which the motor driver made by chopping a DC current with respect to the instruction from the Brain. So we need to prepare a DC power supply for the Stepper motor system.

We starts with the Voltage rating,,

There is a straight forward & safe formular commonly used in the industry,
V=32 x SQRT(Coil Inductance in mH)
you can go higher but just watch out for the motor temperature.

EG,
My coil is 3.5mH
Vdc=60V

Secondary Voltage of the Transformer
Vsec=(60V+1.4V(voltage loss of rectifier))/sqrt(2)=43.4V
common transformer off the shelf are, 6V, 9V, 12V, 24V, 36V, 48V.
So, 48V is my choice. this will give
48xsqrt(2) -1.4=66Vdc#


Current rating
Most will follow the convensional wisedom and add up all the max.current rating of the motors & call that the PSU's current rating.... Nothing wrong when its a small system with total 6 Amp of current, but with a full size machine, the motor max rating of each motor can be 7~8 Amps... if there are 4 motors, the DC is 50V, that will require a 1400VA~1600VA about 2hp!!! That will be huge, heavy & expensive!

One must understand that we normally don't use up all the power the motor can do, i.e. the rated power... the motor will only produce "enough" power to move whatever they we designed to do, so it is all too common to see motor rated for 3kw only work 0.5kw with plenty of headroom.

With that in mind, lets do some "value engineering",
We know
we will never run the motor to the max limit because its a bad design practice. we know all the motors don't run at the same time...
Now we need to determine how much current the motor need to move the burden it was entrusted with. again there are more then one way to find the number,
By mathematics model, culculate the weight, inertia, moment... etc of the overall mechanism & find out the torque and hence the power required... I always keep this option last... even if I can, why should I go throught the whole trouble?
By experiment, build the machine, measure the torque required, this is always a good option, but I need to build the machine first....
Empirically, we can measure the current drawn by motors in similar machines.

I went for the empirical method, many reported to run on 300VA without risk of over heating and burning transformers, Even though they have a different voltage rating from mine, 300VA is the figure I need to know.

VA is a very close equivalent to Watt, VA is derive from multiplying the Voltage and the Current, this current is the resultant current and the current of W is the reactance current, but they are very close in number in this case.


Regulated or unregulated Power supply,
Again, common wisdom will pick regulated power supply, but really it is the worst choice for this application.

The nature of the stepper motor operation is such, when stop, they draw near zero current and when they move, they need current immediately or risk loosing steps,

Regulators are not famous for fast response, to ensure they meet the motor demand, they have to have the full power ready all the time, but the machines hardly use up the the max as we know by now, that extra power will turn into heat and wasted...

As for Unregulated power supply, they only give when the load ask and it does have a capacitor to act as a ripple filter & double as a reservoir.

SO since SMPS is normally regulated & the unregulated one are not good in drastic load demand, it is ruled out.

Transformers
There are few types of transformer core, The C-core, R-core, Toroidal & E-I core.
C-core & R-core are not as commonly available as the used to be and that leaves us with Toroidal and E-I core.
Toroidal Core is a more efficient transformer, but it is its efficiency that became its weakness in this application.
Toroidal response to suddent load demand extremely well, so well that it will burn itself when responding.
E-I core is less efficient magnetically, but because of this deficiency,  the hesitation acts as a buffer to protectects the transformers from burning its coil.

So, there you have it,
My best package selection is
Transformer :- 300VA E-I core transformer with a 48Vac secondary voltage
Rectifier :- Bridge rectifier with metal casing, rated over 100V & 25 amp
Capacitor :- 22,000uf @ 100V Capacitor based power supply.

This also turn out to be the cheapest & the least technological advance combination.

Why The Stepper Motor

We have to look back to the type of control system that we select.

Two main types of control system, Open-Loop & Close-Loop.
Open-Loop control:-
The Brain send an instruction to the Muscle and expect the instruction to be carried out perfectly. and never bother to go back to check if the job had benn done properly as told.
Close-Loop Control:-
Commonly named Servo-System. The Brain will send instruction to the Muscle, after completing the instruction, by using encoders the Brain will cross check if its been done correctly,  if there is error, the brain will instruct the muscle to make the correction/adjustmet, & repeat the cross-checking until the brain feels happy.

Another advantage of a Servo system is they can move much faster then steppers.

The first reaction for most will be to use an close-loop system, error correction, faster speed... simply because that is how a healthy person will think. BUT after a quick search, one will learn that a close loop system will cost an arm & leg.... Not willing to hurt the pocket & further complexity, one normally settles for Open-Loop System...

Anyway, most CNC router employ a stepper system as their muscle and they had been proven competent mostly.

A compromise must be made, Generally,

1. One must not skim on specification of the motor, such as power & torque.
2. Eliminate or minimise backlash in the system.
3. One must tune the machine to ensure the motor doesn't

•  loose step, i.e. motor turn but the machine doesn't move. The cause are generally asking the motor to perform acceration which the motor torque are not sufficient to achieve, mechanical friction, Load of machine too heavy.. etc.
• Backlash, this is the term to describe the "free-play" between the to & fro motion, one can introduce mechanical solution to minimise the error or use software to compensate.
• Electronic inteference, one must ensure the instruction signals are transmitted uncorupted by external noise such as EMI, RFI... etc.

There are no free lunch! Stepper motors system is generally a fraction of the Servo-system, so more brain-juice & body sweat is required to compansate the situation. BTW, servo system do have their unique sets of headache to tackle... but that is another story for another article...

When looking at the Stepper motor specs sheet these are the things to look

• number of phase, the modern steppers are normally hybrid 2-phase.
• number of wires,
• 4 wires means 2-coils,
• 6 wires means 2-coils with choice of Bipolar in series or uni-polar (half coils)
• 8 wires means 4 coils with choice of Bipolar inseries, Half coils or parallel half coils.
  

• Coil inductance of each coil. Lc
• Torque.
• Max. Current rating of each coil.

Stepper motor normally runs over 10 times the rated Voltage, so the voltage rating isn't important. To find the actual motor Voltage rating, here is a simplified and safe estimate.

Stepper motor rated DC voltage = 32 x sqareroot(Lc)
where, LC is in mH.

Actually, if the motor doesn't heat up too much, one can go for higher Voltage.

Don't ask me why as the answer will come in a few pages or tech ladden write-up which I am too lazy to do.

Generally,

• Higher the V, we can get higher speed from the motor, if high speed is a necessary, seek out ahigh coil inductance motor.
• Higher the A, we can get higher torque from the motor, check out the coil rating.
• The limiting factor is always the heat during operation, IMHO it is always desirable to have as low a Coil Resistance no matter what...
• Sufficient Torque, too little can't do the job, but too much doesn't always better. just be rational.
  

I/O ??? LPPT#1 ??? Parallel Port??

Lets talk about how the PC communicate with the muscle.

In natural language, The PC is the brain and the stepper motor system is the muscle.

In this specific case, the Intel D945GCLF mobo, is the PC talk to the CNC machine?

To simplify the analogy, lets leave the EMC2 software system, the mechanical structure, mechanism, electrical ...etc out for the moment.

The PC, has a choice to send and receive signals via serial port, USB and parallel port. with EMC2, the choice is the parallel port.

Traditionally, the parallel port is used as the printer port, there are 25 pins which are arranged as per the table attched, can do 8 bi-directional ports, 4 output ports and 5 input ports.

The simplest way to connect the machine & the parallel port is directly via a cable. BUT because the signal strength from the parallel port is not strong, interfering noise can have its way with the signal & the corrupted signal my be of no meaningful use. or if the receiving end is passive or require some "drive" to work properly.
since my Stepper Motot Driver/Amplifier requires about 15mA to function properly, Hence, a buffer stage is used, normally this is made into a separate PCB which are called Break-Out Board or BOB.
I use a PMDX-122 board which I was mislead into buying. You can find plenty of board at half or less price with equivalent of better specifications. Or maybe DIY one for yourself for less the USD10.

The Atom Mobo is Alive!

The motion constrol system requires a PC to work.... obvious isn't it...

For EMC2, we can use Pentium 4 with 512Mb or more. I had a free P3 donated. but it Ubuntu didn't like it... An used P4 of the correct spec will set me back ~RM400, It is the most economical choice but I have a soft spot for the Intel Atom chip...

Purchased a D945GLF box. Its contained  mobo + the N240 processor at RM215. I need to have a ATX PSU, a 2Mb DDRII RAM, and use salvaged LCD monitor, keyboard mouse,  HDD, CD drive.

Plug in all the necessary connectors, slot in the RAM, power up... then all hell broke loose for the next 3 day trying to figure out what went wrong.... after swapping a new DDRII RAM, IDE cable, BIOS battery, keyboard, mouse, CD drive and even another HDD. Eventually, it was concluded that the mobo is faulty and while waiting for replacement, (warranty claim), I got hold of the Dual core Atom board D945GLF2 as they only have this in stock...

Back to me workbench, slot in the RAM, plug in all neccessary connector, set the bios, insert the EMC live-CD & we have this

Ran the latency Test, 15,801ns max jitter is  just what I hope for.

Here is the screenshot (literally) of EMC2

Lessons learnt? Yes, Murphy Law never fails!!! ....

Apart from that, check your PSU pinout!!!

The D945GLF requires  2x10 +2x2 power connectors.

The D945GLF2 requires  2x12 + 2x2 power connectors

Getting the right PSU at the right price burnt up 2~3weeks of my time....

So you are warned.

Featuring EMC2

While settling back in my home town, I found time to evaluate the CNC Controller bits.

After pain staking search and review; I end up PC based CNC software controller
1) Mach3 which runs on Window
2) EMC2 on Linux OS

As I wish to have the flexibility to have the last say on the hardware specifications

I eventually ended with EMC2 which is free open source program. Not that I'm cheap, Mach3 is affordable ~USD100, & you can have a trial version for unlimited period for free, it has all the bell and whistles that any top rank controller programs would have. Moreover, help forums and supporting community are strong too.

It is the believed that Open source Linux OS is practically immune to hackers & deathly viruses which I fear most.

About the software

• EMC (the Enhanced Machine Control) is a software system for computer control of machine tools such as milling machines and lathes.
• EMC is free software with open source code. Current versions of EMC are entirely licensed under the GNU General Public License and Lesser GNU General Public License (GPL and LGPL)
• EMC provides:
• a graphical user interface (actually several interfaces to chose from)
• an interpreter for "G-code" (the RS-274 machine tool programming language)
• a realtime motion planning system with look-ahead
• operation of low-level machine electronics such as sensors and motor drives
• an easy to use "breadboard" layer for quickly creating a unique configuration for your machine
• a software PLC programmable with ladder diagrams
• easy installation with .deb packages or a Live-CD

It does not provide drawing (CAD - Computer Aided Design) or G-code generation from the drawing (CAM - Computer Automated Manufacturing) functions.

• It can simultaneously move up to 9 axes and supports a variety of interfaces.
• The control can operate true servos (analog or PWM) with the feedback loop closed by the EMC software at the computer, or open loop with "step-servos" or stepper motors.
• Motion control features include: cutter radius and length compensation, path deviation limited to a specified tolerance, lathe threading, synchronized axis motion, adaptive feedrate, operator feed override, and constant velocity control.
• Support for non-Cartesian motion systems is provided via custom kinematics modules. Available architectures include hexapods (Stewart platforms and similar concepts) and systems with rotary joints to provide motion such as PUMA or SCARA robots.
• EMC runs on Linux using real time extensions. Support currently exists for version 2.4 and 2.6 Linux kernels with real time extensions applied by RT-Linux or RTAI patches.

EMC2 is precompiled with Ubuntu 8.04 LTS (long term support) versions for ease of installation and longevity.

EMC2 has a few GUIS, Namely, AXIS, TkEmc, HALUI. They even has a Ladder Logic program call CLASSICLADDER. For now, I'll concentrate mainly on AXIS which is an ongoing development.

Screen shoots

Balik Kampung

Its been nearly a decade since I arrived in Sandakan; Now, it is my time to balik kampung.

I'd withness the transformation from a quiet town with empty road after 7pm to traffic congestion till 10.30pm. From RM1.50 plate of economic mixed rice c/w free chinese tea at the wet market to today's RM4.50++ bowl of kon-lau-man at any kopitiam & you have to pay for you sky juice. The resurrection effort of the old town center.

This is a town which will grow on you; With sparse population, vast space with abundance of fresh clean air are there for your taking; Spoiled by the wealth of natural resources this state possess, one don't need to live a stressful life here.

Slowly but surely, this place had transformed from a timber cowbow town to a small oil palm city, with tourism industry creeping in unannounced.

I'm going to miss the stress-free lifestyle & fantastic seafood Sandakan had indulged me lavishly. Most of all, the sincere and friendly locals that tool me in as a part of their community.

Group Buy, Group Build

The picture of a group of like interest stranges from all age group and all walks of life going after the common goal intrigues me.

I promised myself to jump on any group buy and group build activities regardless.

After years of waiting & fantasizing, nothing ever happened.... @#$%@#

Inspired by the big slogan from spam letter
"One's life is in one's hand",
"You are your own man",
"Be the lord of your life",
"Opportunities are for those who created them"

I took on the task to organize a group buy for ClonAc 2.5.

My friend said " You are a brave man..."

Well, I'm just a the very early stage of this activities and I already had a taste of the things to come...

Followings are some of the "intelligent" questions I get from PM that came along,
"Why don't you do xxx or yyy?"
hey, if you think xxx or yyy is better, why don't you organise one?

"What do you think of xxx, yyy ?"
hey, get appropriate answers from appropriate forum....

"I prefer MMM, wish you luck.... "
I'm only interested if you are interested in my group buy, I couldn't care less about your MMM.

"I would rather buy QQQ & ZZZ"
Go buy la... you don't need my approval!!!

"So expensive! Can't you do any cheaper?"
If its cheap, I would have just buy them myself and do whatever I like at my leisure. I do group buy for the quantity discount, if you join we get better discount la...

"I don't know if I can trust you"
Ya... right... As if you are the only one facing risk... As if it is easy for me to trust you.... do you know if you decided to withdraw from the group buy, I have to fork out money to pay for your promise....

Well, there are many good appropriate suggestions & questions too, which I took very close to my heart, thousand thanks!
"Make sure the supplier is a reputable one, some do disappear after receiving payments"
"Don't over look the packaging & handling cost"
"Don't promise anything that you are not sure of"
"Careful with potential pre-mature withdrawal"
"Final quote will be higher then initial estimations"

There are reasonable request too
"I'm near you, can I borrow your place & tools?"
"Could you teach me how to solder?"
"I know nuts about all this, could you guide me along the way?"

I said "Why not!" to these requests

ClonAc R2.5 or is it ProAc Response 2.5 Clone

Always like to build my own audio equipments. Give me a sense of self reliance.

There are so much snake oil stories about HiFi stuff...

No matter how much denial, in my humble opinion, Hifi equipments are trendy stuff, during a certain period, everyone rush to high power SS, another time, flea power Single Ended Triode amp... etc etc...

Recent hot press is fullrange driver which denounce the existence of the olde trusty passive crossover...

Why something which everyone accepted for the last couple of decades and stable forte of super high-end loudspeakers suddenly gets this type of negative treatment...Is this due to lack of crossover design know-how (just like the case of nfb)? The proof of the pudding is in the eating. So, I gave myself a great excuse to embark on a pair of well documented famous ProAc Response 2.5 Clone build.

I have to make clear that I design & built many Single Full Range drivers when I first started playing with loudspeakers for a couple of years, but that is because I know nothing about passive cross over and single drivers makes my learning manageable.

The choice are enormous, but I quickly set my eye on the ClonAc for its strong following and involved Dr. Troels Gavensen with 6 versions of crossovers to play and learn from.

My experience with cabinet building, box tuning along with the well documented clone will eliminate all the hassle in this aspect. Moreover, when I do some maths sanity check on the design, they really look like good text book example.

I can concentrate on experiment and learning the crossover without destractions from other elements. It's time to move on from 1 way to 2 ways loudspeakers....

The only draw back is the cost. All drivers are Scan-Speaks, commonly used in High End/price loudspeakers.

When there is will, there is a way.

To achieve lowest capital outlay & generate interest in this shrinking local DIY activity. I took the plunge to organise a Group buy and Group build in Diyparadise forum & Lowyat forum. There are response, interest are plenty but the price held many back.

Lets see how it goes...

CNC Rules!

To general public, CNC is synonymous to precision accuracy. This had been engraving, so when ever CNC is mentioned, a picture perfect scenario of flawless component of any kind will pop out in thin air... Snap beutifully and flawless in anyway...
"This will redudant the engineers, technician and operators..." Some say,
"Just tell the machine and you will have all sorted out perfectly... " the other follows
Like instant noodle, not many actually pay attention to the process of making instant noodle "instant". Overtime, misconclude that it only takes 2 minus to make a bowl of soup noodle... sad isn't it...
Try throwing a piece of raw material to the CNC machine and say, "machine this into a ball for me", and see what will happen.... Exactly, nothing will happen.
CNC machine of any kind is another piece of machinery that requires human to opera, not just any human, but skill machinist.
The strenth of CNC machine is that they can provide consistancy, machine consistancy. But they couldn't care less if what they are doing are correct or safe. they wouldn't bother if the cutting tool will break with the size of cut, they wouldn't care how the finishing with turn out... all this require careful programming by skill engineers, technician or machinists.
So, be warned,

PC Based Controller

The recent phenomenon in hobbyist CNC boom could have been contribute by the progress made in PC based controller software. The flexibility offered by the software and minimal computing power, open up the gateway for hobbyist into the once secluded CNC arena.

There are host of controller software available, some are free, the most popular is the Linux based EMC2. Some are pseudo-free... i.e. trial download with unlimited period, with some function limited. Such as Mach3.

Presently, I'm torn between the GNU free licience Unbuto V8.03 based EMC2 & Window XP based Mach3. I don't believe good things can come free but the Linux family is exception. The Mach3 is affortable at US$150 a pop once you are done with the free trial version.

Since I can't decide which is the clear winner, I'll have a creak at both.

Decisions, Decisions, Decisions

Decision is the pre-requisition of any action.

How to come to a decision?

Information, knowledge and experience are the basis, with good analytical sense, assimilate oneself into the subjective circumstances, we can make an appropriate decision for the situation.

In my humble opinion, there are no right or wrong decision. It is how appropriate a decision is.

Why MechMate?

Lets look at various aspect of the design to simplify the analysis.

1) Linear Transmission,
This employs rack and pinion,

• Leadscrew/ball screw to operate in the length involved will face undesireable swirl into oscilation, rack & pinion does not suffer this naturally.
• Cost effective then ballscrews.
• More rigid then Belt & pulley
• More precise then Gear & sprocket.

b) V-groove wheel on angle guide

• Cost effective the linear bearing on rod guide and linear slide on precision square fuide.
• Lower resistance and friction then bush or metal to metal bed.
• Sufficient rigidity
• Sufficient accuracy
• Easy to implement

c) Monocoque Y-Gantry & Z-Car Body

• Light weight
• High rigidity
• Running gantry over x and y-axis is most foot print efficient
  

d) Stepper Motor + Micro-stepping Driver

• It is cheaper to set up an open loop motion control then close loop servo motor system.
• Microstepping improve smoothness of transverse motion.
• Accuracy is well within requirement

e) Well developed PC Based Controller.

f) All material and mechanical parts can be source locally.

f) I already has the tools required to construct one.

g) Plenty of scrounge opportunity to fits the machine to my wallet.

h) My research shows that this design is so well thought through.

i) I don't think I can find or design one that is as good as this

j) The is a free plan by enthusiast, very professionally done, more detail then many paid plans that I'd came across over the years.

DIY CNC Router

There are many approach to own a CNC machine, you can buy one of those industrial CNC machine center or you can build one with recycling printer stepper motors, some bearings and guides.... For me, I'll skip the baby toys and jump straight to building a Mechmate; A full fledged real McCoy CNC router. Like this one here.


This beautiful design is the work of Gerald. D, he generously give away his design for free and will provide selfless support from his forum. Thumbs up to Gerald.

Why not design myself? Surely I can, if I spend the next 10 years on it... And since this thing isn't going to be cheap to build, I might as well take the "safe" path and get it to work as-soon-as-possible.

I will build one that can take in a full size 4' x 8' sheet. wood based material such as plywood, MDF, chipboard.. etc. Soft metal such as aluminum, bronze, copper. Plastics such as Teflon, Darline, acrylic, prospect, polycarbonate... etc

My Spec.
working size : 2440mm x 1220 (8' by 4')
Tool head : 2.2kw Water Cooled Inverter Controlled High Speed Spindle head.
Drive Motor : NEMA 34 stepper motor
Motion Control : PC based
Precision : +/- 0.01mm

Had been spending like no tomorrow for the past month and the spending never stops....

I am scheduled to start construction by end September or early October....

Wise me luck...

Re-Tinker CNC

A quick Google and we have more then a few pages on home build CNC machines of all sort...

There are 4 major components that make up a CNC machine
1) The tool head
2) The linear motion
3) The Motor drive
4) The controller

The tool head is what one decide to use the machine to achieve, be it lathe, milling, punching, grinding... etc. The criteria has not changed much since the industrial revolution and I do not foresee much changes in the near future. The new comers are water jet, plasma cutter, laser cutting, EDM or even 3D printing. These had revolutionized how many things are done and I will expect more to come.

Linear motion used to mean linear motion in X, Y and Z axis, but today, it does include rotational movements around the axis, which are called "DoF" Degree of Freedom. The design considerations involves size & material of work piece, speed, accuracy required, finishing requirements. is how the tool and work piece move with respect to each other.
Fix toolhead with moving work piece? Fixed workpiece with moving tool head? or move both partially?
Tranmission & motion conversion from rotation to linear motion,use mechanism such as lead screw & nut, belt & gear, rack & pinion, gear on chain...
Rail guides to ensure transverse in straight line using linear bearing on rod guide, roller on rail... etc

No drastic changes from what I learn in my school days...
I think I'm still pretty up-to-date in this area.

The greatest different were the controller and the motor driver development and availability.

The drive system, for stepper system, it consist of the stepper motor and driver; for the servo system, it consist of the servo motor, encoder and the motor driver.

Today, micro-stepping driver are available at an affortable price, I think this is the main reason for the CNC boom in recent year. Well within hobbyist pocket size.

Servo system too has become much more affortable, but still has room to go.

Only a few years ago, 'serious' CNC machine are built with a customized controller console with its own computing capacity and PC based controllers are in their infancy.

The controller takes in G-code, A.K.A. command list and send control signal to the driver which consequently operate the stepper motor.

What is G-Code? Its a code that the controller take in for processing and the code normally starts with 'G'. Serious... eg, G 00 means stop, G 19 is move to... etc

There are software that convert .dxf files from most CAD programs to G-code, or one can write the G-code manually. I'm still looking into such programs presently.

Currently, there are many affordable, pseudo-free & free PC based controller software, they all have active supporting forums, the two that cough my attention are Mach3 and EMC2.

Mach3 is a window based controller software, it is free until you decide to "go commercial" with it. USD150 will buy you a pop.

EMC2 is a Linux based open-source controller software under GNU license. This thing runs real time kernal, all the bells and whistle and more...

I think I've reach my typing limit for the day... blurry vision...tired finger joints...

How I Got Myself Into This Mess

Lately, I'm feeling the effect of aging working against... Soldering differed due blurry vision, workshop progress halted as my back ache...

Without much to do, I stared at the monitor and decided to retrace how I get myself into this mess.

I started in metalworking,
I learn welding and machining in my polytechnics days.
Woodworking is a hobby.
Electrical came naturally.
Fabrication is a big part of my day job.
My engineering skill grew through work and play...
Self-thought practical electronics to fill in the blank.
Analytical skill & experience are symbiotic...

Discounting those dismembering alarm clock events and bicycle repairs, the first "serious" machine I built was in my polytechnics days.

Its a stepper motor driven X-Y table carrying a high speed spindle. We build the X-Y table with Acme-lead screw and linear-bearing running on surface hardened guide rails.

My part in the project is the Linear Motion portion of the project, i.e. X-Y table, the motor & the spindle. The challenges were to design and build a light and rigid X-Y table which carries a high speed spindle, this table will transverse accurately to the stepper motor rotation.

The designing was easy, we were given the required leadscrew pitch, x and y treavels, estimated loads and the desired tolerance/accuracy. Throw all these info in salad bowl and came out with a set of CAD drawings of the "ingenious" design. Even tried to model a finite element analysis but not complete due to time constrain.

As ball-screw was expensive then as now, we opt for to machine ACME screws in the workshop & the Anti-Backlash nut and holding blocks while were at it.

After gathering all the part, shower after shower of welding spatter and flying grinding sparks, we got everything assembled. The hardest part was to align and tune the finished assembly. I can still remember how much easily metal flex under load and the agony of getting everything line-up precisely... Till this day, I'm still puzzled how we pulled off the project in such short time... Nevertheless, that was great fun and my inauguration into machine building.

Maybe I should re-kinder with CNC machine for old time sake...

Tools

Tinkle and tools hoarding are symbiotic...,The more I tinkle, the complexity grew... Need for more tools... Or was it the other way round?

Ah.... those polished-shiny-blinking tools...
The growing tool collection and the size of my junk box are the physical evidence of my tinkering journey... or is it my impulsive shopping habit...

The tool collection growth irrespective of the current global economic outlook... When time is good, you buy cos you have the moola; When time is bad, you buy because you have plenty of time to play....

What's New?

I made a quick listening to the 6DJ8 preamp. As most tube amp that I build, she sounded good. but not great. Usual tube sound characteristics are present. Clean, crisp, sexy mid range... I should further tinker with the component values to tune for "optimum" result but there are so much distraction in this materialistic world...

My new toy had arrived...


Dress in Red,
Miniature,
Slim
Comes with bottoms...
And Spikes....
Just the type I like...

Impossible to keep my hands away...



Downloaded the open source Arduino environment here

Plug in the USB port

Set the Dip switches

Load the scrip

Press the biggest keyboard key

and

Blink! Blink!! Blink!!!





I herein solemnly declare I'm Micro-Processor Enabled!!!!

Wah Ha HA HAAA!!!

These Came with the kit,

All the bells and whistle


That Says.....






More to come!!!!!

Completing the Schematic

Now, lets finish off this before my new toy arrives.

Lets organize all the numbers that we had determined.


input is assume to be 1Vrms so Vp=1.414V

#additional note, normally, we will try to bias the tube at least 0.5V away from 0V grid, to prevent grid current, but in this case, the gasin of the stage is so high that before we even get close to 1V of the 0V grid, the power stage should have over loaded. so it doesn't matter.

DC state
B+=300V
Vp=90V
Vbias=1.3V
Ip=15mA

RL=14kR 3W
Rk=86R 1W
Rg=1MR 1/4W

PS resistor = 2 x 200R 5W
PS Reservoir cap = 22uF
1st stage Filter cap = 68uf
2nd Stage Filter cap = 68uf

Arduino

It has been a few years since I’d started to look for a mean to start on micro controllers stuff. PIC is the recommended chips as I was told they are cheap and abondon locally.

Bought many books and spent hundreds of hours surfing the net with no fruitful progress…. These books eventually became my best cure for insomnia… It never fail to put me to sleep in 20 minutes…

Everything which I found require me to build some thing, either a programmer or hardware to actually make the micro chip work… Its too much challenge for me… so the search continue

Found this book while wondering aimlessly in my local book store a month ago.

By Massimo Banzi, co-founder of the Arduino Project. Published by Make Magazine.

The cover cough my eye.

“Arduino” has appeared with increase frequency in my google search for how-to starter packages for electronically challenged beginner like me. I didn’t dig this AVR based board as I was looking for PIC stuff. What a mistake!

This is the only book on MCU which I finish reading in one go… and awake!

I learn what Physical Computing meant, Arduino uses C language, everything is open source, the board contain the necessary hardware to operate and plugin USB.

Arduino is “ready-to-go”, no need to know about bootloading, I/O connections, I2C, USB chip, communication chip... etc etc which I couldn't care less, so that noobies like me can get our claws right into the fun part.

There is a growing community such as
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl
Seriously fun ppl.

and their web page is packed with great stuff such as ready made codes/programs, meaning we don't have to reinvent the wheel!
http://www.arduino.cc

The potential application is only limited by your imagination! We can do useless thing with it such as teaching our flower to call for help when they get thirsty, lights off in the absent of occupant, control an autonomous robot, intelligent home system, track the sun, control an miniature UAV, feed the monkey, skin the fish.... all of which you can jump straight in as long as you know what make things tick, perfect toy for tinkerers.

Just placed an ordered a "clone" Arduido starter pack, (wanted to go for the real thing but they have the best shipping charges.) should arrive by next week, can't wait to blink some LED....

The Basic Circuit

I was forced to learn up Eagle to produce this circuit.

Tube Curves is Your Friend

Common stereotype misconceptions that tube design is for tube gurus with in-depth tube knowledge, Master Yoda-ish character and is one-with-the-force; In reality, anyone who is competent in prevent/avoid electrocution while working with high voltage and still remembers Ohm’s Law is competent enough. All you need is the data sheet. Allow me to demonstrate.

Firstly we get hold of the 6DJ8 data sheet as follows:-







You can start by determine the max and min safe work condition, gain, Rp, rp, plotting the best loadline… etc.

BUT I WON'T!! I will reserve that for your self-amusement during your dreary hours…

Use the Data Sheets recommendations and get straight to it before the irrational impulse of building a tube preamp subsides.

From the #Page 1 of the Data Sheet we have
Filament voltage, Vf = 6.3V,
Filament Current, If = 365mA
From this, we calculate the power required by th filament Pf = Vf x If = 2.3W

#Now write down this on your shopping list, “ 6V, >2x365mA (1A is common),transformer”

At the end of #page 2, "maximum rating, absolute value"
Series grid Resistor = 1 megohm max

you will find "Typical Charateristics" and the followings

Plate Voltage, Vp = 90V, This is the voltage across the anode and cathode
negative grid voltage, Vg = 1.3V, this is be the Bias Voltage
Plate Current, Ip = 15mA, with triode, Ip= Ik, cathode current

Now some maths,

Find Rk, using Ohm's Law,

V=IR
R=V/I
Rk = Vbias/Ik = 1.3/0.015 =87 ohm #

Determine B+,
We will use Isolation Transformer, In my part of the world, main power is 230V AC,
Using Isolation Transformer with a bridge will yield,

Raw B+= Sqrt(2) x 230 = 325V,
we will filter raw B+ to 300V

VLoad = 300V - Vp - Vbias = 300V - 90V - 1.3V = 208.7V #

RLoad = VLoad/Ip = 208.7V/15mA = 13,913 ohm we can choose 15K resistor.

Well after all this hard work, I need to get my regular coffee fix.... We'll continue on the next installment

How to Sound Like Tube Guru 101

How to Sound Like Tube Guru 101

Common Cathode CC is name as such because its Cathode is connected to the Common Ground.

The CC is good at Voltage amplification, i.e., magnify signal; this is generally the strength of glassware.

It has high input impedance of easily a few hundred thousand ohms; in plain English, it is very sensitive to input signals and very easy to drive.

Fairly high output impedance, which means it is not so good at driving difficult or less sensitive loads such as Solid State Amplifiers and Loudspeakers without some neat tricks but its sufficient to drive another tube stage.

Biasing, to get the tube into operating condition, we set the DC bias or quasient state, its like getting your car on idle speed; When AC signal (yes, signal can only be AC, that includes noise signal too) is applied, its like stepping on the accelerator, and the engine will respond accordingly to how hard you step on it

There are 2 biasing methods in general, Fixed-Bias and Self-Biasing. My emphasis will be on Self Biasing as IMHO they are easier to tinker with and better sounding too.

Self Biasing means we put something (resistor, LED, Diode, Battery or Constant Current Sink) between the tube’s cathode and the ground so that it can generate the required bias voltage by themselves, hence Self Biasing.

Input signal, lets consider CD player output signal of 1Vrms, that means 2.83V peak to peak. V max of +/-1.414V.

You don’t need an input capacitor solder in your circuit as CDP already has an output cap to do the job.

Output coupling. We are going to use Capacitor coupling. This capacitor will ensure only signal voltage is delivered to the next stage. That’s all you have to know for now.

Recite the above to your pal is enough to impress your tube ignorant buddies.

Common Cathode Amplifier

Common Cathode Amplifier

Glass-tech is over a century old…. How hard can it be????

To cut short the chase, we will pay exclusively attention to triode for now. This should spare us from pages upon pages of boring tech-loaded content. Jumping straight to Common Cathode Amplifier (CC from here on), will speed up the whole process even further.

There are more then ample articles written on the basis theory in the net, spend some effort to google will reap fruitful return. I'll leave this to the readers to decide.

CC has its strength and weaknesses, but hey, it constitute vast majority of audio circuit in its plain or modified form, that speaks strength for itself.

Tinker with Tube Circuit

To begin with, my motive was learning electronics. I wasn’t looking for that illusive “Tube Sound”, as I was neither an audiophile nor interested in Hi-Fi. As the matter of fact, I don't even know what "tube Sound" meant!!

Fortunately, from my day job, I learn enough electrical safety practices to avoid electrocution. Nevertheless, it is an act of plain stupidity to take on 230V D.C. without paying due respect lethal aspect of electricity.

With help from very patient and persistent and unselfish cyberspace friends from all corners of the globe, I made leap and fold progress. Friendship sprout rapidly among like interest people. Its like I’d found my second childhood that I never had, it has been a fulfilling journey.

Today, through the journey, I'd beginning to have the ear for good sound and developed my own preference. I do my best to go for the best possible sound at least to my ears when designing and building amplifiers. It feels satisfying.

Tinkering 6DJ8

6DJ8 is the tube of choice, small signal triode, with 2 triode encased in one glass envelope.

It has a large family which is fully compatible, namely,6922, 6N1P,6N11, ECC88, EC88C, E88CC, E188CC, E288CC, .

Plenty of tube rolling opportunity.




It is good sounding, wide applications. It's high Gm, medium gain and low Plate Resistance. With some circuit tinkering, we can build quality Pre-amp, Buffer-amp, driver for small power SE amp, headphone amp... etc

IMHO the only tube which will sound normal when connected as cascode.

There are plenty of NOS (New Old Stock) available, as well as current production.

Tube Tinkering

Toobs!

Quote
"In electronics, a vacuum tube, electron tube (in North America), thermionic valve, or valve (elsewhere, especially in Britain) is a device used to amplify, switch, otherwise modify, or create an electrical signal by controlling the movement of electrons in a low-pressure space."

Wikipedia


A century old tech, their place in this modern world are limited to large scale signal transmission thank to its robust operation capability.

They some how managed to survive the guitar amp industry due to various aesthetic and nostalgic sentiments.

Mythologized by modern marketeers with hypes limited only by imagination. This glass ware is gaining support in the HiFi consumer market as well.

We get increasing impression of tube amps being more art then technology... IMHO, when we don't know the actual science behind a technology, it is most convenient to save face by branding them as art....

Despite all my negative impression on the sales slogans, I truly love the "Tube Sound", its as close to paradise as one could get.

In the coming articles, I'll share my tinkering journey with 6DJ8. I'll talk about some theory and specification stuff but I do my best to spare tinkerers with heavy doze of boring theory stuff instead just outline the essential start tinkering with tubes.

Circuit Theory for Tinkerers

Like it or not, we need some basic Circuit Theory for tinkering in electrical and electronics gadgets.

BTW, changing a plug, replacing a wire, spay some paint does not count as tinkering in my book. When I tinker, I dig deep.

Where did I picked up the circuit theory know-how?

All Engineers took electrical classes somewhere along the academic route; We enter the classroom, went through the motion of listening to the teach/lecturer, collect all the handouts, do some tutorials and off we go to the exams… to return the knowledge in written form. Hopefully, some of these knowledge will residual in our brain. In my case, Ohms Law, power and summation of component value calculation stayed….

Lucky me, enough for tinkering and be dangerous.


Ohms Law

V = I · R

V is for voltage, V is the unitI
I is for current Ampere, A is the unit
R is for Resistance, Ω ohm us the unit.

From here, we can derive the following equations

I = V / R

R= V / I

Power

P = V · I

Where,
P for Power or Watt, W is the unit
V for Voltage across the component
I for current running through the component

Summation of Resistance

Series Connected Resistor,

R_total in series = R₁ + R₂ + R₃ + … + R_n

Where,
R_total is the resulted total Resistance of the series connected resistors
R₁, R₂….Rn are the Resistance of individual resistor

~handy tips,

When connecting same value resistor in series,

Use This --> R_total = R_individual x Pieces of resistors

Parallel connected Resistor,

R_total = ((R₁)^-1 + (R₂)^-1 + (R₃)^-1 + …. + (R_n)^-1)^-1

Where,

R_total is the resulted total Resistance of the connected resistors

R₁, R₂….Rn are the Resistance of individual resistor

~handy tips

When connecting identical value Resistor in parrallell

R_total = R₁ / pieces of resistor

How to use them?

• Ohm’s Law enable us to figure out how much voltage is across the component and how much current going through the component.

• We use this as the minimum required ratings, i.e. current, voltage and watt rating of the components. *PS* For Power rating, give it at least a double,I triple when I have the chance.

• Summation of resistor allow us to add/reduce R_total in the circuit. By changing the R_total, when use with Ohm’s Law, we can figure out how to adjust the current and voltage of the circuit and/or components. Which is an essential know-how for tinkering.

Computers and Micro Processing Unit

My inaugurate experience with computer was the Sinclair ZX81, a present from my aunt during my primary school days.

It displays a green screen on home TV. It was also the first time I actually learn something by reading instruction manual. Manged to write simple BASIC language program to occupy the screen with numbers and alphabets, make them blink, change color and make some beeping tone... etc all the usual big hoo haa at that time. I was never successful is saving any programs on tape recorder as described.... Also we can play Pong with it.

At the end, I annihilated it in the search for higher wisdom.

My next "serious" encounter with computer was in my polytechnics days when the syllabus requires CAD drawing on a Prme Medusa system, FORTRAN77 and 8051 mcu programing. The 8051 is a populated PCB baord and a 2 x 7 segment display and a input keypad which we used to punch in HEX machine code. We happilye blink some LED, excitedly make the Knight Rider running light and a traffic light as course work. Frankly, I didn't learn anything from here as my attention was on those sweet young thing around.

I then used WordPerfect in the uni's computer lab to write my final year project, the great graphics features and lovely spell check made my life much more bearable.

Then came the windows, the internet, Netscape, IE, the dot com bubble... and I was happily going along with the flow.

Until a few years ago, a fellow audio diyer built a NOS (Non-OverSampling) DAC with 3 DAC chips, namely the TDA 1541, 1543, 1545. He used a mcu to control relays for selection of chips for AB test. Another made source selection with mcu controllered relays. This sparks some interest.

For the pass 4 years, I'd been trying to start tinkering with mcu but some how it didn't happened. Firstly, I don't know where to start, and when I did, I don't have a programmer, then then training kit was too expensive and I'm too lazy to built one, one hurdle after another.... consequently, a netural death...

Why I Tinker?

I am cursed with impulsive curiosity toward the how's and why's of "things" works, just couldn't help it.


To deal with this curse, I dig and strip anything that fancy my curiosity. Eventually, I'll build a similar "thingy" base with some variance as proof of concept. One thing lead to another, I end up a hobbyist carpenter + machine machinist + metal worker + electronic technician and whatever is required of me to make it happen.

Tinkering with things is how one learn the working principle of things and deal with my incurable decease.

For the past few years, I embarked on electronics "thingy" because I am really an electronic idiot. DIY audio equipments seem to be the right track to teach myself electronics... again, one thing led to another, I design and built more then a few tube amplifiers and loudspeakers.

This blog will be my platform to share my learning experience with the like mind people and hopefully will start a few friendship along the way.

Maybe someday... after I'd satisfied my appetite for electronics, I'll proceed with shipwright... who knows... For sure its a bigger money pit.

Until then lets do some soldering, hole drilling, welding and metal cutting.