dual power supply

Hi everyone! I just want to ask if it is possible to create a split or dual supply power supply circuit from a car battery source??

Any comment or suggestion will be much appreciated?

Hello Erwin

Yes, creating a split powersupply from a car battery is possible. The supply will depend on the amount of voltage that you want the power supply to deliver. The simplest version of a power supply would be to connect directly to the car battery. This would provide 12 volts positive and 12 volts negative (although most batteries will deliver about 13.8 volts and have some pretty nasty voltage spikes up to 30 volts or so, due to the alternator)

A simple regulated (Very little to no voltage spikes) version of a power supply would involve LM7805 and LM7905 voltage regulators. This would supply 5 volts postive and 5 volts negative, and some heat.

You can make a variable regulated power supply using the LM317 and LM337 IC's, but because all voltage regulators will drop the voltage output by about 2 volts, the best you could get would be around 9-10 volts split supply.

If you need an output supply higher than the input supply, you'll have to do some work with a torroidal transformer and some additional circuitry. If this is the case, I suggest looking at some car audio amplifier schematics, as they will almost always require a voltage higher than 12 volts.

So I guess this leaves it up to you...what kind of output are you looking for?

Please be a little more specific on what voltage and current you would like to produce. If you are using the - or frame of the automobile as the common, the only way to generate a - voltage with respect to the frame is with a voltage pump for low currents, generally less than 100ma. If you require more current then it can be accomplished with a switching circuit.