Author Topic: Home Brew Analog Computer System  (Read 106970 times)

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Offline SeanB

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Re: Home Brew Analog Computer System
« Reply #25 on: January 10, 2013, 11:42:39 am »
A soft flexible thermal pad on top of the transistor and the thermistor on top of that. Cover them all with a small potting box that is left unfilled, but glued to the board to keep draughts out. Mostly isothermal, enough thermal mass to keep both stable and simple. Can't remember the manufacturer of the soft pink foam thermal transfer pads that are so common on CD drives.
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #26 on: January 10, 2013, 12:10:37 pm »
That sounds like a plan. I could fold up some little rectangular cans out of brass or copper shim and solder them up along the seams. The SOIC could be enclosed by a (say) 50 thou-thick, rectangular perimeter GND track to which the up-turned can gets soldered - a bit like an RF screening can, but just to keep air currents out instead.

Or perhaps I could just glue a plastic coke bottle screw-cap onto the board.

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Offline SeanB

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Re: Home Brew Analog Computer System
« Reply #27 on: January 10, 2013, 12:22:38 pm »
Not metal, you want insulation, not extra capacitance. Small potting box, matchbox inner tray or even a cardboard cut and glued to suit ( I did this for a crystal as an oven) will work. Even styrene sheet cut and scored, stuck together with glue and held down with some double sided tape.
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #28 on: January 10, 2013, 12:28:18 pm »
Cardboard isn't very robust and is a bit shabby. I'm liking the glued down plastic coke bottle cap right now.............   
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Offline SeanB

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Re: Home Brew Analog Computer System
« Reply #29 on: January 10, 2013, 12:36:21 pm »
Pulling a Bob Pease now are we..... He did the same on a thermally sensitive appnote, inside a biscuit tin, on a sheet of copper clad board with a lot of dead bug.........
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #30 on: January 10, 2013, 01:09:04 pm »
I vaguely recall seeing it done as you describe but couldn't say if it was Pease or Williams. It might have to be soda water bottle lids though as I'm giving up coke. I actually drink the soda water straight. Tastes better than tap water and the bubbles are refreshing. I somethings get funny looks at the supermarket with my weekly 8 liters of soda water though. They must think I'm a major piss pot or something.

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Offline ftransform

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Re: Home Brew Analog Computer System
« Reply #31 on: January 11, 2013, 03:15:36 pm »
I vaguely recall seeing it done as you describe but couldn't say if it was Pease or Williams. It might have to be soda water bottle lids though as I'm giving up coke. I actually drink the soda water straight. Tastes better than tap water and the bubbles are refreshing. I somethings get funny looks at the supermarket with my weekly 8 liters of soda water though. They must think I'm a major piss pot or something.
lol, I like to drink mine with raspberry syrup. I can't stand the taste of that shit without sugar. :-\
« Last Edit: January 11, 2013, 03:17:27 pm by ftransform »
 

Offline baljemmett

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Re: Home Brew Analog Computer System
« Reply #32 on: January 11, 2013, 03:19:47 pm »
lol, I like to drink mine with raspberry syrup. I can't stand the taste of that shit without sugar. :-\

Ninja edit?  ;)
 

Offline SeanB

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Re: Home Brew Analog Computer System
« Reply #33 on: January 11, 2013, 04:12:53 pm »
I just make my own, why pay full price of carbonated water when the gas to make 100l is the same cost as 5l of soda water. Carbonated water is the same price as cooldrink, but they save because there is no cane sugar or any other thing in there.
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #34 on: January 15, 2013, 12:35:17 pm »
Generic 1.25L soda water at Foodland cost $1.   :P

But that is enough on that exciting topic; I've been verifying my design of the computers precision, triggered Time Base on breadboard.  :-/O
Attached is a pic of a small part of it operating. The Time Base is the master unit that basically controls the whole computer, generating
the logic signals to control the computers integrators (which have 3 modes; "Hold", "Initial Condition" and "Compute/Integrate"), as well as
providing a voltage ramp output representing computation time, so the solution can be displayed/plotted on an X-Y oscilloscope or on chart recorder.   

I need a scope with more vertical channels...............................
« Last Edit: January 15, 2013, 10:50:42 pm by GK »
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Offline GK

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Re: Home Brew Analog Computer System
« Reply #35 on: February 09, 2013, 11:50:44 am »
Since this is unarguably the most interesting thread started in the history of EEVblog forum, I probably shouldn't let it die.

I got the power supply design for the sine/cosine function chassis completed/operational/tested this afternoon. This is the supply board that provides precision regulated rails of +/-110V and +/-51V, as well as the required +/-15V low-voltage supply rails, for nine sine/cosine function module boards and the single 100V triangle waveform generator. The circuit diagram *.pdf is attached. The 4 transistors mounted on the large heatsink are the series pass devices for the HV rail regulators.

The regulator was specifically designed not to have any overshoot or other funny business on power-up and power-down and also features an over-voltage detector / fault latch to shut down in the event of a loss of regulation to any of the HV rails. A scope photo is attached showing the lack of overshoot on power up.

The PSU is shown powering the triangle wave generator. The unfinished sine/cosine module board is also in the picture; I'm still waiting for an back order of 0.1% resistors to arrive, which are the only parts still needed to finish populating the PCB. They should arrive next week. Once the sine/cosine module design is tested I'll be producing another 8 of them. That will complete the electronics for the computers "Sine/Cosine Function" chassis.



 


« Last Edit: February 09, 2013, 11:54:26 am by GK »
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Offline robrenz

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Re: Home Brew Analog Computer System
« Reply #36 on: February 09, 2013, 12:46:30 pm »
Very nice stuff GK.  :-+ I had not followed this thread. Now I see why you are not jumping on the differential amplier project.....yet  ;D

Offline veryevil

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Re: Home Brew Analog Computer System
« Reply #37 on: February 09, 2013, 08:32:03 pm »
This is just some beautiful work. I cannot wait to see more.
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #38 on: February 11, 2013, 03:24:31 am »
Thanks  :)

I'm looking foward to being able to make a start at running some elementary programs, but there is still a lot of PCB layouts and soldering to do until then. I'm working on the various PCB layouts for the computers master controller unit now (very much analogous in operation to an old school CRO timebase). That will be a major step in the right direction.

BTW, does anyone know an affordable source of PCB tin plate power? For the integrator banks (the brain of an analog computer) guarded jfet input currents need to be minimised to prevent drift in the "hold" mode of operation. Therefore I don't want to conformable coat tp preserve the copper and need to board wash after soldering.
« Last Edit: February 11, 2013, 03:30:17 am by GK »
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Offline FenderBender

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Re: Home Brew Analog Computer System
« Reply #39 on: February 11, 2013, 03:32:24 am »
GK I really like this analog computer stuff. Is your knowlege of analog computing just accumulated from years of experience? Do you have any resources on them? I'd really like to learn about them. Shall I start on analogmuseum.org?
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #40 on: February 11, 2013, 03:33:57 am »
Very nice stuff GK.  :-+ I had not followed this thread. Now I see why you are not jumping on the differential amplier project.....yet  ;D


Hey, you know with your machinist skills and workshop facilities you'd be able to construct something pretty impressive if the analog computing bug ever bit.
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Offline GK

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Re: Home Brew Analog Computer System
« Reply #41 on: February 11, 2013, 03:37:28 am »
GK I really like this analog computer stuff. Is your knowlege of analog computing just accumulated from years of experience? Do you have any resources on them? I'd really like to learn about them. Shall I start on analogmuseum.org?


90% of my knowledge on the operation of analog computers comes from stuff downloaded from analogmuseum.org. Download all the stuff in the library section (the big Systron Donner text is the best introduction). Also try to find a copy of the Korn and Korn book (I picked one up last week form a sechondhand book seller).
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Offline robrenz

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Re: Home Brew Analog Computer System
« Reply #42 on: February 11, 2013, 01:09:51 pm »
Hey, you know with your machinist skills and workshop facilities you'd be able to construct something pretty impressive if the analog computing bug ever bit.

"Please don't feed the animals" thanks but I am sure that you are like me and don't need any help getting distracted to a new project.  ;D
« Last Edit: February 11, 2013, 06:05:27 pm by robrenz »
 

Offline saturation

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Re: Home Brew Analog Computer System
« Reply #43 on: February 11, 2013, 05:07:49 pm »
You could make a difference engine, aka "mechanical calculator":





Best Wishes,

 Saturation
 

Offline robrenz

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Re: Home Brew Analog Computer System
« Reply #44 on: February 11, 2013, 06:18:44 pm »
That is some very nice work in both cases :-+
IF i was going to do something along those lines it would probably be a 6 foot diameter circular slide rule.  You could get some awesome resolution at that diameter. But that would require some single arc second accuracy angular division which is not easy. Also requires extremely accurate trueness of rotation on the bearings because any rotational runout will give angular error.

Offline megajocke

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Re: Home Brew Analog Computer System
« Reply #45 on: February 13, 2013, 08:41:02 am »
Cool project!  O0  :-+
 

Offline GK

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Re: Home Brew Analog Computer System
« Reply #46 on: February 13, 2013, 10:45:47 am »
Oh no, another audio forum refugee  :) How's it going?
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Offline GK

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Re: Home Brew Analog Computer System
« Reply #47 on: February 15, 2013, 12:20:17 pm »
The last batch of 0.1% resistors arrived today and this evening I was finally able to finish loading the prototype Sine/Cosine module PCB and test it out. It worked just as planned. I haven't calibrated it with a voltmeter or linearity tester yet; just tweaked it while viewing the waveforms on the oscilloscope.

Here are some pics of it operating with the 0-100V unipolar triangle wave from the calibration/test oscillator used as an input signal.
To recap, the Sine/Cosine module accepts a positive input signal ranging 0V to 100V representing phase angle, which is scaled to 3.6 degrees per volt, so 100V=360 degrees or two pi radians. The output has a scaling factor of 100, so sin(90) and cos(0) = 100V and sin(270) and cos(180) = -100V. In the cosine mode the module generates a continuous sinewave output from the 100V triangle wave test signal.

Now I have another 8 of the Sine/Cosine boards to complete. I’m keeping a tally of the computers total component count. The PCB’s for the finished Sine/Cosine function chassis alone will contain a grand total of:

2252 resistors.
808 diodes
805 transistors
349 capacitors
51 trimpots
29 voltage reference ICs
27 single op-amps
18 quad op-amps
10 inductors
9 dual comparators
9 555 timers
9 reed relays
9 trimmer capacitors
4 CMOS digital ICs
2 regulator ICs
2 DPDT relays
2 diode bridges
1 quad comparator
1 crystal
« Last Edit: February 15, 2013, 12:29:42 pm by GK »
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Offline robrenz

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Re: Home Brew Analog Computer System
« Reply #48 on: February 15, 2013, 12:42:25 pm »
Awesome work there GK :-+ Makes me feel electronically inept :'(

Offline GK

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Re: Home Brew Analog Computer System
« Reply #49 on: February 15, 2013, 12:52:44 pm »
Yeah I'm pretty awesome.
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