Powering a sub woofer, in my car

[hamdiya]

Hello good folks at electro-tech

I have a small sub woofer which is connected to my computer and would like to now try it out in my car. (as you might have guessed, my car's audio system, well, that's being too generous, it's crap!)

I'd like to temporarily go with a cheap solution and install the sub woofer connected to my computer, in my car. I've had past experience with making normal desktop speakers run on batteries (hook up a 9V to the transformer output and it works like a charm. If you're interested in doing this, be sure to disconnect the transformer output wires before you hook up the 9v battery). I tried doing the same to my sub woofer but i got stuck when i saw the center tap from the transformer.

I've drawn a diagram showing the transformer output. Find it attached

How can i get power to my sub woofer from my car's 12v supply? Mind you that max power consumption is about 25W

I have thought of a DC/AC inverter, but a good one is too costly, and installing a proper sound system will put an even bigger hole in my pocket. Cant afford that at the moment.

Also, on a different matter, what program can i use to draw circuits and have them converted to strip board layout?

Thanks everyone and have nice day

 

[stevez]

You'll need to know (and share with us) the power requirements of the subwoofer. 25 W is a start but what voltage? Is it AC or DC?

 

[hamdiya]

Well, AC of course ("I've drawn a diagram showing the transformer output."). The AC is then rectified to DC through 8 diodes. 4 for the 'left' coil and 4 for the 'right' coil. Voltages are shown in the picture.

The maximum power consumption could reach 25W, give or take.

 

[audioguru]

The transformer might make 15.5VDC times two or it might make positive 15.5V and negative 15.5V.

Why bother trying to blow up the sub-woofer's amp by connecting the power wrong? It probably doesn't have enough power to be used in a car. 25 Whats might be only 4 Watts.

 

[hamdiya]

I don't quite follow you, sorry.

Would the ultimate solution be to get a DC/AC inverter?

 

[stevez]

I have a small subwoofer/amp and the power supply is separate from the amplifier. That would easily allow substitution of an alternate power source (DC in my case). I am still not sure I understand what you have. As Audioguru indicated, the transformer in he sketch allows for several possibilities.

If your transformer/rectifier/filter 16 volts or so you could power it directly from your car and accept some loss in power. I would agree with Audioguru in that if you make a mistake you've ruined your amplifier. The other problem with this approach is that you'd have to add protection from the high voltage transients that are present in auto electrical systems. If your power supply is different than this would not work at all.

If you can't power it directly then you'd need to construct a power supply, probably switched mode, to deliver the DC power needed in place of the existing AC supply. That by itself it likely more trouble than it is worth. Here in the US an inverter (DC to AC converter) that might do the trick can be purchased for modest amounts of money - but so can an amplifier that is powered from the auto electrical system.

 

[hamdiya]

Thanks for the input.

It seems like it's more trouble than worth it. Here in the UAE, you can get a standard 60W inverter for about $12 and a branded 100W inverter for about $35. I'd go with the $12 one but with any cheap electrical product (especially in this case cause you'd be dealing with 220V) spells trouble to me.

Today i got an idea while in the shower. I could bring a pairs of 12v rechargeable batteries and use them to power the sub woofer. Arrange them so that there is a center tap common between them, just like in a transformer. Once they run dry, charge them in the car. Of course there will be safety precautions so i don't blow up my car's battery and ruin the electrical system Sounds like a lot of work, but then again, I'm also doing this for the fun of it and by just buying an inverter would beat the purpose!

I really don't have much worries about wrecking my amp. Got it for about ~$15 in a bargain.

Any ideas on the solution proposed above?

 

[HarveyH42]

You can get car amps an sub-woofers dirt cheap from pawn shops (crack users either steal them from each other for rock, or get tired of being beaten up for rattling people's windows when they drive by). So places are putting limits on noise levels and enforcing them. Might get a good deal at a police auction as well.

 

[hamdiya]

I went ahead and tried my method and it worked good. Problem is that given the noise from the engine, its not much different from my current 'audio system'. I don't see any reason to continue and make a new power supply for it.

You can get car amps an sub-woofers dirt cheap from pawn shops

Sad to say there are no pawn shops here Guess i'll have to wait until i got enough dow to spare to get a good sound system.

I just want to say thanks to everyone for providing your support. Good to know there's a place to get help when you need it most.

 

[palesha]

it is not difficult to make dc/dc convertor. The circuit is available on Rod elliot site. Only problem is getting the ferrite core & transformer wound as required.