On 11/05/2010 10:00 PM, Mike Raiford wrote:
> 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?
>

Definitely not 30 mA and yes nixie tubes, retro even in 1975 :-)
At the time I was working for Burroughs and components were not a 


flops etc. It had an alarm function and you set the time/alarm by 
dialling in the time using rotary switches. A couple of years later I 
worked for Motorola and made a clock from CMOS. That ran on a pp3 battery.

>  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
>

File not found. :-(

>
>> You are mad, you know ;-)
>
> Yeah, I know ;)
>
>> Does your wife know about this ?
>
> She does. She's surprisingly tolerant of my antics. ;)
>

I suppose it keeps you off the streets. :-)

>>> The TTL version should be fun, too. I plan to have lots of LEDs to show
>>> what's happening inside the machine.
>>

Good luck and photos are required. :-)

>> 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.
>
>

I suppose if you use reed relays it will keep the power and noise levels 
down.

-- 

Best Regards,
	Stephen

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