Voltage divider 12v>5v

[zebbedee]

Hi,i am a complete novice when it comes to making electronic circuits so require some help,i am reasonable at soldering though so hopefully will be able to make a circuit.

I need to know how to make OR where to buy a voltage divider which could be made to make an old style car rev counter(12v) work with a newer engine(5v),these things are available to buy i have been told but the price is quite high for something that i have been told is relatively simple.

Its a while back now but the item i saw only had 4 wires coming out of it,

1, switched 12v
2, ground
3, rev counter output
4, >to vehicle rev counter

can anyone help?

 

[MikeMl]

Two resistors will make a "voltage divider":

 

[zebbedee]

Two resistors will make a "voltage divider":

ok thanks for the reply,are those the correct sized resistors i would need? and with me being a complete novice on this how would i get the 4th 'output' with the circuit you have given in the picture ie i need 1, switched 12v 2, ground 3, rev counter output 4, >to vehicle rev counter would the rev counter output be the 'in' and the 'out' go to the rev counter which requires the 12v?sorry i just find this kind of thing hard to take in

 

[MikeMl]

I misunderstood due to the bogus title you put on this thread. You have an OLD Tach and a NEW car, therefore you need to amplify the the amplitude of the pulse train.

This circuit does what you need. Total Cost ~$1. Pinout for the 2N3904. The circuit has four connections, too.