| Electronics > Projects, Designs, and Technical Stuff |
| Home Brew Analog Computer System |
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| GK:
After many other diversions I'm back to allocating time to this ongoing project again. I've finally competed all 30 of the programmable integrator modules and have them attached to their brackets and ready to be chassis mounted. Should get them chassis-mounted this coming long weekend, and at least partially wired. As pictured earlier in this thread, I've had the panels drilled and the 366 banana jacks installed for over a year already. Also have the sine/cosine circuit boards completed and an order for another ~ 1000 4mm banana jacks has recently arrived, so I have some further panel drilling to get on with...... The (twenty) Summing and (ten) Logarithmic amplifier PCBs are currently underway..... The integrator board assembly was a little tedious as I had to pad the "timing" capacitors to the correct (measured) values. There are two selectable timing capacitance values. 10nF is permanently wired into the integrator and an additional 990nF (for a total of 1uF) is switched in by a reed relay. In each example I got the 990nF to within 1nF and the 10nF within 100pF. For low dielectric absorption I used polypropylene for the bulk of the capacitance (at least 820nF and 8n2 respectively) and padded with COG ceramic for the 100's of pF and polyester for the 10's of nF. Low value (nF's) polypropylene capacitors only seem to be available in very large packages with high voltage ratings (like 2kV and 1" lead pitch) and are expensive. The polyester was the most cost effective option. Back in the day the big analog computer manufacturers had custom polystyrene caps made to uF values with fraction of a percent tolerances - somewhat beyond the DIY budget. The low-leakage summing junction clamp/protection diodes at the JFET0switched inputs are heat shrink covered to keep out the light as discussed here: https://www.eevblog.com/forum/projects/glass-diode-photoelectric-effect/ |
| T3sl4co1l:
Wow! |
| Dave Turner:
Have you estimated the total power requirement of the finished product? Apologies if this has already been answered. |
| GK:
The computer is being built in modular units, each with it's own self-contained, regulated power supply. Each unit, housed in either a 2U or a 3U case will contain, in general, ten identical computing units - a computing unit being either an integrator, a summing amplifier, a multiplier, a comparator, a logarithmic amplifier, etc. The "integrator chassis", for example, of which there are three, for 30 computing nits in total, is a 3U case. Power consumption per integrator chassis is about 40W. |
| Dave Turner:
I, for one, eagerly await the completion of this project or at least it being sufficiently complete to demonstrate with a video or two. |
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