JamesNewman

11 anni fadiscuss

A couple of reasons. Firstly its dynamic behaviour, If I'd known about the 1us gate propagation time earlier I may have tweaked the componentry a bit. The second reason is that it may have picked up some of my mistakes such as transposing the outputs or missing off some pullup resistors.

JamesNewman

11 anni fadiscuss

I have to confess that power efficiency wasn't/isn't top of my list. As it happens the parts you suggest don't feature on the Farnell website which is where I did my selection. I use the L-1334SRT. I can't now remember quite how I chose it but I'd have been looking for some combination of brightness and cheapness and availability. I would be budgeting 10mA per LEDs as that's the kind of number I was used to, if it didn't want more than that then that was all I asked on the power side of things.

JamesNewman

11 anni fadiscuss

I did do a lot of simulation of the logic. I built models of the hardware in software (C++). But I didn't do any analog simulation, which was a mistake. I was aware of SPICE and had a look around but the tools I found seemed expensive. It was only after I'd started that someone pointed me at some free versions, LTSPICE in particular.

JamesNewman

11 anni fadiscuss

The cost is a rather embarrassing £20k. The biggest cost is the circuit boards about 7 or 8k now I think. The simple hardware such as the aluminium, nuts and bolts etc was a few thousand. Cables and connectors were thousands. I've had to get 300m of ribbon cable so far and its not going to be enough ! There's about a thousand connections. The proper electronic components transistors/resistors/LEDs not as dominant as you might expect. There seemed to be just an endless amount of stuff that was needed.

JamesNewman

11 anni fadiscuss

I never really thought of using relays, just not into them. There's a chap called Harry Porter someone mentions below who has built a processor out of relays which looks very impressive. My starting point was that I was trying to learn about transistors and was looking for ideas of something to build.

JamesNewman

11 anni fadiscuss

Not at the moment, I'll try and remember to have a look at that next time I test a module. Currently everything is shuffled into the corners so I can start the construction of the decoder frame.

JamesNewman

11 anni fadiscuss

I have a unicycle ! But never mastered it. Furthest I've managed was a metre or so and most of that was falling. But if I put the processor on casters it might support me as I pushed it along on the unicycle. Got to be worth a try...

JamesNewman

11 anni fadiscuss

I saw the Babbage machine when it was first built at the Science Museum. It is truly beautiful.

JamesNewman

11 anni fadiscuss

I'd be delighted if there was enough interest and a way for it to be on public display. But there's a way to go yet.

JamesNewman

11 anni fadiscuss

Extrapolating from the three frames so far it's looking about 48A at 5V, so 250W. Nearly all of that is for the LEDs.

JamesNewman

11 anni fadiscuss

I hadn't realised people would be so interested ! I'll try and answer some of the questions that have been asked.

I just use a single type of MOSFET, the 2N7000. I did look at BJTs (in fact the whole thing started because I wanted to teach myself about "proper" transistors) but working out what resistor values to use to cope with varying fanouts/ins etc was too scary for me. One of the fundamental drivers when making design choices was that I really really want it to work when its built, it'll be heartbreaking if/when it doesn't, so I try to favour robustness.

The single MOSFET is also, I'm currently guessing, the cause of the slow speed. If you look at how the professionals (chip makers) do gates they tend to have two versions of the logic, one driving the positive case and the other driving the negative using both P and N MOSFETS. So the output is actively driven either way. My circuits only actively drive in one direction and rely on a pullup resistor (the 10ks) to generate a 1 output. Halves the number of transistors I need, but cripples the speed. I need to do some experiments to prove/disprove that.

I am planning on putting the design files on the website.

And I'm in Cambridge UK as opposed to Cambridge MA.

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