I am working on a formula style car and creating a digital dash based on an Arduino. I currently have a signal from the ECU running at 12v DC and a varied frequency depending on the RPM of the engine. What I need to do is lower the voltage to 5v DC and maintain the same frequency, with as little frequency noise as possible on the output. Is there a good way to do this? Do Voltage Regulators keep frequency, or at least keep some sort of ratio?
UPDATE – SOLVED
My team and I just realized yesterday that we can use the CAN-BUS signal straight out of the car and just comb through the data for what we need. A little bit more coding, but way easier in the long run. Less wires too 😀
Best Answer
If the load that needs to be driven by the resulting 5V signal is fairly high impedance then a simple voltage divider would be all that is needed to reduce the 12V signal down to a 5V swing.
Voltage dividers begin to be a bad solution if:
So I would suppose that you are using a timer/counter input to the AVR microcontroller to read the pulse frequency. The input impedance of this is very high as long as you keep the internal pullup/pulldown resistors turned off. In this case of voltage divider of 12K up and 5.1K down should do the trick quite nicely.
Do be sure to check the output of the ECU to make sure that the 12V signal makes full transitions from GND to 12V. If it does not go way to GND it may require some additional signal conditioning to be able to feed the signal to the AVR.