Hall Effect Generator/ RPM sensor

Hi there,

I have a rpm sensor that I want to interface to an Arduino. I am not sure what I need to search for?

It is on an old Starter/Alternator test bench and is used to drive an analogue gauge. It has a shaft driven straight off the front of an Alternator/Starter Motor.

I have run up the sensor and I get out of the 2 wire an AC voltage which varies depending on speed. I got out 500mV AC just running it up with a drill at full speed.

I want to interface it to the Arduino but I am not sure what to do with AC voltage. I am using an MCP3208 for 2 other circuit as the resolution wasn't enough with the 10 bit onboard ADC.

Any help would be much appreciated.

Well I have had another idea.

Is it possible to convert the signal to DC without too much loss.

I could then use an instrument amplifier to increase the signal for the Arduino?

Any ideas?

Cheers,

I think you would need the instrument amplifier before you convert it to DC, as a simple diode will take 700mV to turn it on. Look at things like a synchronous detector circuit or a true RMS conditioning chip.

Thanks very much for that. It will give me some areas to look into and hopefully solve my problem.

chippa71: Hi there,

I have a rpm sensor that I want to interface to an Arduino. I am not sure what I need to search for?

It is on an old Starter/Alternator test bench and is used to drive an analogue gauge. It has a shaft driven straight off the front of an Alternator/Starter Motor.

I have run up the sensor and I get out of the 2 wire an AC voltage which varies depending on speed. I got out 500mV AC just running it up with a drill at full speed.

I want to interface it to the Arduino but I am not sure what to do with AC voltage. I am using an MCP3208 for 2 other circuit as the resolution wasn't enough with the 10 bit onboard ADC.

I would use a LM393 comparator to convert that AC into a 5V square wave, feed that into an Arduino digital input pin, and use the Arduino to measure the frequency.

I'm dealing with the same kind of problem, can't get pulse counts with a hall sensor. The signal is now 0.9V above ground, do you think if i would use a comparator to set it to 5 V , the arduino would recognize it easily? Or doesn't it make a lot of difference with the signal i have now? (small amplitude, need to count frequency to measure wheel speed)

Thanks anyway!

Yes, if you amplify the signal to 5V using a comparator, the Arduino will recognise it easily.

You could also try using the analog comparator built into the Arduino microcontroller, although that requires more programming knowledge.