Digital stop watch 2011-06-18

3lectrix submitted a new article:

Digital Stop Watch - A digital stop watch built around timer IC LM555 and 4-digit counter IC MM74C926 with multiplexed 7

A digital stop watch built around timer IC LM555 and 4-digit counter IC MM74C926 with multiplexed 7-segment LED display. The MM74C926 consists of a 4-digit counter, an internal output latch, npn output sourcing drivers for common cathode, 7-segment display and an internal multiplexing circuitry with four multiplexing outputs. The counter advances on negative edge of the clock. The clock is generated by timer IC LM555.The circuit works off a 5V power supply. It can be easily assembled on a...

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OK, thanks
Please let us know the accuracy of this device.
You employ one 8 pin & one 12 pin IC.
I have not checked the size, or pin spacing, but I'd expect that both will present soldering difficulties for all but the very experienced.
5V supply also will present problems, it would require a dedicated supply or at least regulation of a 6V battery. So why not design for (3 x 1.5 = 4.5) or 6V batteries?
A rotary switch is far from ideal when timing short duration events with any level of accuracy, has an alternative been investigated?

what software that used ?

I builted this, and added a 5 volt regulator. At first it didn't work. I double checked every thing retraced all circuits and did a final trouble shoot at the timer and what I found was a defect on the schematic. R1 feeds, but R2 and R3 need a junction at the top side. As you look at the schematic it looks like two seperate circuits. Dialed it in with a scope gets pretty close.

what is the oparation of digital stopwatch?

i built this too.but can't work.
press resest ,the led display 8888.so ,please tell me what happen?

sifiso said:

what is the oparation of digital stopwatch?

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does it worked after making changes ??????

what if we directly connect R1 and R3 and neglect R2 ?????
i guess it will work !!!