Car 12v to 4.5v resistor circuit needed for low current device

What resistor circuit is needed for a low current trafic alert device
which can be plugged into the courtesy light?
The traffic alert normally runs on 3 AAA batteries, but a terminal has
corroded off... }:-(

Happy with a soldering iron and vero board

cheers
Richard

 

Attach a 1 kohm resistor between 12 volts and the device you want to power.
Measure the voltage at the device. If the voltage is below, decrease the
resistor until you obtain 4.5 volts. Now add a 4.5 volt zener diode because
the vehicle voltage can vary from 7 up to 15 volts.

Harold

 

Thanks for that and other info have helped cheers

 

Thanks for that and other info have helped cheers

 

You shouldn't need much:
http://www.radioshack.com/product/i...tId=2103679&kw=dc+power+adapter&tab=techSpecs

Or, you could use a hash choke, a transzorb, and a regulator to do pretty
much the same thing. ;-)

Cheers!
Rich