How do I create a voltage drop?

[BigAl1956]

I have a return signal from a mass airflow sensor of 1.1 to 1.2 volts at idle. I need the voltage to be .9 What do I need to put in line to drop voltage? Dio? Resistor? or what? And what ever it takes as far as a part, I need a part number of said part so that I can have a 2/10ths of a volt drop.

Any help can be e-mailed to bigal.1956@netzero.net

 

[Comcokid]

Not knowing the output impedance of your mass airflow sensor, it's a little difficult to answer.

However, I will assume that you mass airflow sensor is a low impedance output (assumes the sensor has an active device on the output - i.e. an op-amp). I will also assume that the input to your ECU is high impedance. In that case, all you need to do is to use a resistor voltage divider. You can do this using two resistors.

Use a 2.4K Ohm resistor and a 10K Ohm resistor. Put the two resistors in series. Connect the free end of the 2.4K to the sensor output, connect the free end of the 10K to signal ground (perferable the ground lead of the sensor, or the ground at the ECU, wherever you're locating the divider). Connect the ECU wire to the connection between the two resistors. This should drop the voltage by a factor of .806 (1.2 V x .806 = .967 V or 1.1 V x .806 = .887 V). But note - this will drop the voltage by this factor at all times, even when you're not idling.

This could also be done with a trimmer or pot - one end to the sensor output, one end to ground, and the wiper to the ECU. You could then adjust for the voltage you wanted. However, the adjustment may be touchy.

 

[jesse75]

BigAl1956,

I'm curious as to what you're working on?

jes from sunny florida

 

[Doug020668]

Hmmmm, sounds like you may have a problem that you may be disguising by trying to artificially force the voltage down.
Why do you believe you need to drop the voltage. if the voltage is that high in the 1st place, maybe you need to find the cause of the problem.

Or, are you trying to modify another component to suit your vehicle? If so, you will need to ensure that the voltages are correct throughout the entire rande of operation, not just at say, idle.

I would like more info on what you are trying to achieve before I say more