Hot-wiring a power supply

[ack79]

Does anyone know how to make a power supply provide voltage while it is not connected to a motherboard? I have a couple old ones and would like to use one to power a 12 volt car stereo in my room. I have an ATX type with one connector and also a pre-ATX with two connectors.
Thanks

 

[bcastner]

This is not such a good idea. I was going to type "not such a hot idea" but the fact of the matter is it could be a very hot result.

The power supplies were built presuming a certain minimum load on them at all times. I think they would last only a few minutes after you turned the radio off.

In addition there is no shock protection whatsoever for you or anyone else with such a use.

You should be able to find an AC - to - DC converter at Radio Shack or similar that could provide the power. But the antenna then would be a problem. Most car antennas depend on the body of the car to act for the antenna as a ground plane. While this too could be worked around it will not be as trivial as you might think.

I vote no on this project. Sorry.

 

[G0AOZ]

I agree with bcastner.... Probably not a good idea. Also, depending upon your radio, you might find the computer PSU causes interference on the signals you're trying to receive. Make sure whichever DC power supply you obtain is of a suitable rating (amperage), otherwise distortion of the audio will be apparent on music peaks.

The aerial and ground system shouldn't be a problem. Yes, the metal body of the car acts as a groundplane, but unless we're talking about fringe area reception (poor signals), a few bits of wire ought to do the trick. Assuming you're wanting FM VHF stations (88 - 108MHz), a vertical piece of wire about 30" long for the aerial (inner connection) and, say, 2 or 3 pieces of wire also 30" long connected to the outer connector (where the braid would ordinarily connect), spread out roughly horizontally to simulate the car bodywork. Or, if it's more convenient, run the 30" aerial wire vertically up from the radio connection and just one earth wire vertically down from (braid) connection. The first configuration is known as a quarterwave groundplane aerial, and the second is a halfwave dipole.

You might need to move this configuration around within the room for best reception. The close proximity of objects like radiators, waterpipes etc., may enhance or decrease the received signals. Trial and error...

Good luck!

ROGER - G0AOZ.

 

[ceh4702]

There is a company called I-Tuner that has a Yahoo shopping site that sold 60 Watt DC-DC ATX POWER supplies that were just basically a small board 7 inches wide that is designed to plug into a Mini-ITX motherboard. They also sold small AC-DC external power converters rated at 55 watts to plug into the DC-DC power supply board. I dont know what the watt rating is on a car stereo, but hopefully it isnt too high. Might try Radio Shack also.

You really need to make sure you get the right amount of amps/wattage for the device. I think the conversion process uses some power up to create the DC.

If you do not like my post feel free to point out your opinion or my errors.