[time-nuts] Digital Clock kit - no Integrated circuits!

Bob Camp lists at cq.nu
Sat Jan 9 14:51:26 UTC 2010


Hi

Yes indeed.

A lot of this was worked out a very long time ago. Most of what you see on the net these days is simply an IC circuit broken out into a bunch of discrete parts. IC's have different issues than discretes.

Bob

On Jan 8, 2010, at 10:46 PM, Bruce Griffiths wrote:

> 
> At high temperatures the circuits with the additional diodes in series with the base will have problems with transistor leakage currents when all inputs are low.
> The person who created that page doesnt know how to design reliable circuits.
> A base to emitter shunt resistor is one way of avoiding this problem.
> 
> Bruce
> 
> Stanley Reynolds wrote:
>> Knowledge of history doesn't = having lived it :-)
>> 
>> http://www.play-hookey.com/digital/electronics/dtl_gates.html
>> 
>> 3 to 1 is not all that odd if you have 5 to 1 and 2 to 1 ratios as the page above indicates.
>> 
>> Stanley
>> 
>> 
>> 
>> ----- Original Message ----
>> From: Bob Camp<lists at cq.nu>
>> To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>> Sent: Fri, January 8, 2010 8:10:34 PM
>> Subject: Re: [time-nuts] Digital Clock kit - no Integrated circuits!
>> 
>> Hi
>> 
>> It seems like the diode to resistor ratio is a bit off in that design.
>> 
>> In order to go into further detail, I would have to admit to starting out in the pre-integrated circuit logic era ....
>> 
>> Bob
>> 
>> 
>> On Jan 8, 2010, at 8:07 PM, Tom Clifton wrote:
>> 
>> 
>>> http://transistorclock.com/  has a very interesting (though a bit expensive) kit for sale.  A 10" x 11" circuit board sporting nearly 200 transistors and 600 diodes to drive six seven-segment displays.  Suitable for framing...  As delivered runs on 60hz but there is a note about conversion to 50hz mains.  You can buy a  bare board, just the components or a full kit.
>>> 
>>> You must see it to believe it!
>>> 
>>> Tom
>>> 
>>> 
>>> 
>>> 
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> 
> 
> 
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