We're working on a car where we've replaced most of the electrical system. We've also replaced the transmission, and the new gear box doesn't have a speed sensor that we can use for the instrument.
We're replacing that with signals coming from the ABS-sensors but passed through an ECU.
The signal generated by the ECU is a 0-12V square wave with frequency linear to rotation speed (0-800Hz). The instrument takes a sine wave signal with varying frequency. We need help designing a circuit to achieve this conversion.
We've previously tried simple solutions
But for whatever reason (not sine-like enough?) it's not working.
Super thankful for any help! At work right now so my only tool for drawing graphs is paint. Sorry.