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ahly20
Apprentece
Egypt
8 Posts |
 Posted - Dec 16 2005 : 12:53:56 PM
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i wanted to run my cd-rom in my car, & i found the wanted circuit in this site, but it worked just one time and every time i try it it works at home very well but just i atatch it in the car the regulators is burnt. i thought about the (+)cable and the ground one does it really make difrunt
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Dec 19 2005 : 09:49:25 AM
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What circuit did you use? How and where did you connect it to the car? How is it switched on an off? Do you have any surge protection at the input of the circuit (kickback diode, capacitors, MOVs)? Run any wires near ignition wires?
Lots more info is needed to figure this out.
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ahly20
Apprentece
Egypt
8 Posts |
Posted - Dec 19 2005 : 10:49:14 AM
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i used the circuit in this link http://www.aaroncake.net/circuits/cdsupply.htm
and added other regulator for 12V.
the input cable is taken from the cigaret light"already removed" and switched on & off by regular switch without surge protection.
what is driving me creazy is that it works at home verry well "after using 12V transformer to simulate the car" but i can't figure what happens in the car.
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Dec 20 2005 : 09:06:45 AM
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The 12V regulator needs at least 13.5V or so in order to function. It can be common, depending on the car, for the electrical system to drop below that. You also need a heatsink on the regulator because most CDROMs will draw more then 1A. Also, if you are using the LM7812, it is not powerful enough as it's maximum current is 1.5A.
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ahly20
Apprentece
Egypt
8 Posts |
Posted - Dec 20 2005 : 12:28:59 PM
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i already used a heatsink & i even added a fan to the circuit and what can i put instead off regulator iff it cant work proberly
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Aaron Cake
Administrator
Canada
6718 Posts |
Posted - Dec 22 2005 : 09:38:25 AM
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There are higher current versions of the LM78xx series regulator available in TO3 style cases. Check National Semiconductors site for info and datasheets. There are also "low overhead" regulators as well, that only need about 0.5V above their output voltage at the input. Those are much better.
Aside from that, there's not a lot you can do unless you move to a switching supply or first step the voltage up to above 15V or so then regulate down.
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plz help
