Hi
I want to put a tachometer onto a milling machine. I purchased one of these..https://www.ebay.com/itm/280903275997 and it looks good. I had IR sensors QRD1114 so used them. I was able to construct a circuit on the bench and scoped a square wave (squarish, rounded edges) with a peak to peak of about 3.2 volts but the meter seems to display a fraction of the RPM. On the milling machine, it seems to be about 1/60 of the actual. I am waiting to hear back from the supplier but less than optimistic. The pulse train on the bench from a hobby motor and a disc **broken link removed** seemed about right although at first I felt the pulse train was off ie I thought the motor was spinning a lot faster than what the meter said but cannot tell. The period of the waveform varied fine with a variation in the motor voltage. I do not know why it would be different. Any ideas? The only literature on the tach is what you see on the eBay posting. I am considering upgrading my circuit to switch a mosfet for a more precise pulse train but since it all works, I don't think this will make much of a difference. Any ideas?
I don't have pictures to post but the circuit is simple. The output of the sensor passes current to a resistor in the collector leg, generating a pulse train. It is the fraction of the actual speed that stumps me. There are two buttons inside the unit but again, no instructions.
Anyone have any input?
I want to put a tachometer onto a milling machine. I purchased one of these..https://www.ebay.com/itm/280903275997 and it looks good. I had IR sensors QRD1114 so used them. I was able to construct a circuit on the bench and scoped a square wave (squarish, rounded edges) with a peak to peak of about 3.2 volts but the meter seems to display a fraction of the RPM. On the milling machine, it seems to be about 1/60 of the actual. I am waiting to hear back from the supplier but less than optimistic. The pulse train on the bench from a hobby motor and a disc **broken link removed** seemed about right although at first I felt the pulse train was off ie I thought the motor was spinning a lot faster than what the meter said but cannot tell. The period of the waveform varied fine with a variation in the motor voltage. I do not know why it would be different. Any ideas? The only literature on the tach is what you see on the eBay posting. I am considering upgrading my circuit to switch a mosfet for a more precise pulse train but since it all works, I don't think this will make much of a difference. Any ideas?
I don't have pictures to post but the circuit is simple. The output of the sensor passes current to a resistor in the collector leg, generating a pulse train. It is the fraction of the actual speed that stumps me. There are two buttons inside the unit but again, no instructions.
Anyone have any input?
