On 5/11/2010 2:31 PM, Stephen wrote:

> Feck! About 35 years ago I built a digital clock out of TTL. It used 30
> amps at 5 volts Vcc. The power supply was bigger than a modern PC.

30 AMPS? O_o

Umm, you sure that's not 30mA? I mean... for a digital clock 30 amps 
seems like an unreasonably huge power draw! Were you using nixie tubes 
for the display?

 From this data sheet:
http://www.jameco.com/Jameco/Products/ProdDS/48119.pdf

A max if 15mA for a decade counter. 66 of these would draw one amp of 
current. To draw 30 amps you'd need:

~2000 chips.

Of course, if a classic 7400 series, it's a different story:

http://www.jameco.com/Jameco/Products/ProdDS/50690.pdf

Still, that's over 700 chips to get that kind of current draw.


> You are mad, you know ;-)

Yeah, I know ;)

> Does your wife know about this ?

She does. She's surprisingly tolerant of my antics. ;)

>> The TTL version should be fun, too. I plan to have lots of LEDs to show
>> what's happening inside the machine.
>
> I hope that you have comprehensive fire insurance :-P

We do! I think ... I better read my policy closer... I expect the relays 
will use quite a bit of current, which is why I want to be able to keep 
the thing as small as possible in the number of relays.


-- 
~Mike

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