View Full Version : Voltage Divider to change 12V to 5V

07-18-2006, 08:38 PM
Hey, guys...

··· I am working on a circuit that has a clean, filtered 12V input.· there is one component in the circuit that has a maximum Input Voltage of 6 Volts.· I have VERY LITTLE room for components and I am very cramped.

··· Does it seem feasible to just use a voltage divider with a 330ohm resistor and a 220ohm resistor (bringing voltage down to 4.8V?· If the input Voltage is clean and filtered, idealy the output of the divider should be stable enough...am I correct?

-circuit attached


07-18-2006, 09:15 PM
· It's not recommended to to that.
· The reason is that the voltage will change according to how much current the IC is using.
· If it's a gate there is a good possiblity that it will oscillate too.
· I can see it causing all kinds of problems.

· You could probably get away with using a resistor and zener diode.


Cheap 4-digit LED display with driver IC·www.hc4led.com (http://www.hc4led.com)

Low power SD Data Logger www.sddatalogger.com (http://www.sddatalogger.com)

"Remember, you are unique, just like everyone else." Unknown.

Mike Green
07-18-2006, 09:15 PM
With your divider values, the resting current is about 25ma and your sensor could draw up to 2.5ma or so without too much voltage variance. Typically, with a resistive voltage divider, you want the resting current to be at least 10 times the external load. Be sure to use 1/4W resistors since the power dissipation is more than a 1/10W or 1/8W can handle.

Mike Green
07-18-2006, 09:25 PM
Bean's advice is generally correct. It does depend on the device you're powering. Better would be a series resistor and a 5V Zener diode. I'd use a higher value resistor, maybe 470 ohm, for a lower resting current, as long as the device you're powering only draws 1-2ma.