Laser Sensor and Counter

[eptheta]

I have created a circuit which is supposed to detect light from a laser (using a photodiode) and increment a counter every time the light is blocked. It works partially, but sometimes the signal bounces and the counter jumps from 1 to say 4 and then to 5 then 7 etc... it's just unstable. If i flash the laser on and off very slowly, then it registers the count more or less properly, but i want it to detect fast changes, for example me waving my hand back and forth in front of the laser.
Here's a link to the diagram of my circuit. The counter circuit works perfectly, so there's no need to include it.
**broken link removed**

If you can't improve or point out the faults in my design, could you perhaps suggest an appropriate alternative circuit that would suit my purpose ?

If anyone here can help me i would be very grateful.
Thanks

 

[Nigel Goodwin]

You need to implement 'de-bouncing' just as you would with a mechanical switch.

You should also post attachments here, not on a third party site, where people won't bother looking at it (I didn't). Click on 'Go Advanced' then 'Manage Attachments'.

 

[MikeMl]

I went to the third party site and looked, although I agree with Nigel.

Your circuit makes no sense. Why are you using the -5V supply. What kind of gate is between the collector and the counter?

 

[eptheta]

Sorry, i meant 0V not -5V. I am using a TTL Chip with a NOT gate (7404) , basically to convert my variable voltage because of the photodiode to a digital signal.
**broken link removed**

Any other things i'm doing wrong ?

 

[bankai]

can someone teach me how to make an infrared counter( at least 4 digit numbers)???

 

[Reloadron]

can someone teach me how to make an infrared counter( at least 4 digit numbers)???

Hi and Welcome

You would likely do better starting a new thread with your question. Also you need to spell out when saying four digits if you want a maximum count of 9999 or 1999 because it matters though I would assume 9999. Anyway, starting a new thread and clearly stating your objectives would be a good way to go.

Ron