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[on:]

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.

[Reply #1 on:]

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,

[Reply #2 on:]

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.

[Reply #3 on:]

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

[Reply #4 on:]

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.

[Reply #5 on:]

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!

[Reply #6 on:]

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.