Making tachometer using arduino

Other Hardware Sensors
1

Hi, I'm working on a tachometer for my RC car and it appears that there's no other way to do it than using small DC motor as a dynamo. Arduino will read generated voltage and convert it to speed. But I ran into some potential problems. What will happen when there's a small voltage applied to the ground (when the motor spins backwards)? I put a protective Schottky diode D1 there but it will not open until there's at least ~ 0.2 V. Next question is what will happen if the generator spins while the Arduino is off, so there's more than 0.5 V above supply voltage (which is obviously 0V). Will it damage that analog pin? Or does it only apply to digital pins?

Schematic I made: Ulož.to Disk

2

Hi,

You can use this type of encoder. You will get an accurate reading and will solve your problem!

You can also use Dedicated Optical Encoders

Note: You can take help from here.

3

There's one thing I forgot to mention. The Arduino has already a plenty of work to do (among other things processing signals from optical rpm meter) so I don't wanna add anything that generates pulses to be count by the microcontroller. Long story short: it must be done with a dynamo or something that has analog output. But thanks for your post anyway.

4

I've just run a test and Arduino survived.
SOLVED