[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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