Hi all
I have built a lap counter for slot cars. 556 monostable providing counts to 4029 BCD --> 4511 BCD to 7 segment --> LED displays. Originally I placed reed switches beneath the track for triggers. All worked well on bench top but charging the track and running cars send the displays wild. I guessed EMF from the charged track and dc motors so I replaced the reed switches with IR Light gate (IR LEDs above the track and photo diodes beneath). Once again, benchtop was great but when I run the cars there is false triggering. It is now only once or twice a lap, and with some cars only once, at a location where the track is momentarily broken.
I was sure that IR would work and don't know what I could be doing wrong?? Could EMF from the cars be triggering the photodiode? Just to clarify I even took the step of powering the entire counter circuit from a battery completely isolated from the track/cars and still got the false triggering.
Please let me know if anyone has an idea what is going wrong as I am out of ideas.
Cheers
Blue Wolf
I have built a lap counter for slot cars. 556 monostable providing counts to 4029 BCD --> 4511 BCD to 7 segment --> LED displays. Originally I placed reed switches beneath the track for triggers. All worked well on bench top but charging the track and running cars send the displays wild. I guessed EMF from the charged track and dc motors so I replaced the reed switches with IR Light gate (IR LEDs above the track and photo diodes beneath). Once again, benchtop was great but when I run the cars there is false triggering. It is now only once or twice a lap, and with some cars only once, at a location where the track is momentarily broken.
I was sure that IR would work and don't know what I could be doing wrong?? Could EMF from the cars be triggering the photodiode? Just to clarify I even took the step of powering the entire counter circuit from a battery completely isolated from the track/cars and still got the false triggering.
Please let me know if anyone has an idea what is going wrong as I am out of ideas.
Cheers
Blue Wolf