Originally Posted by newimaging
I am trying to use the motor generated voltage as a voltage input for my Phiget board. But on my multimeter I am only getting about 0.065V, but it might be to short of a pulse for the meter to register it. But I don`t think its 4V, otherwise the board would be recognizing it. It does recognize when I tap a 9V battery onto the deadstrip very quickly.
I tried building an op amplifier today, but there was to much noise, so I have to play with that some more.
Dead strip counters are normally designed so the car will still count however slowly it crosses the counter strips. At the risk of stating the obvious, cars that go over the counters a bit slow still deserve to have their lap counted. Motors running slowly produce very little back emf, so simply using the motor generated voltage as a voltage input to the counters will mean the car won't count below a certain minimum speed.
The back emf from the motor will be well over 0.065V unless it's running very slowly.
The voltage will depend on how fast the motor is runing and the motor characteristics.
How fast the motor is running in a car going over the counter strips at full racing speed depends on where the counter strips are sited. It's normal practice to mount them on slow-medium speed part of a straight, so the back emf will be well below the value at maximum speed.
I've done a few tests, and at the sort of speeds the cars go over dead strips the maximum of the waveform is in the range 2 or 5 volts.
Originally Posted by 2FER SLOTS
I was of the understanding that a dead strip worked as a motor "shorted" the two rails.
This would make the small voltage the motor produced a troublesome byproduct.
Yes it is normal to design dead strips to work when the two rails are shorted. This means the car will still count even if the car is just put on the counter strip unpowered (that's a handy way of testing them).
However, counters are useless unless they can cope with cars passing over them at normal racing speed. When moving at racing speed, as well as the back emf quite a few cars bounce slightly going over the counter strip causing a somewhat intermittent signal. This is what is happening so unless the counter design can cope with that reality they won't work reliably.