Hello everybody,

I would need a simple and efficient circuit for a car charger for my portable ham-receiver. The receiver needs 12V and 1A. I have some 7812 voltage regulators and I would like to use them, if possible. The circuit should also be able to eliminate or at least minimize the frequency interferences.
Can somebody give me a hint?

Thank you in advance!

Conrad

 

Have you got an old ATX power supply that still works, you can make a good 12V psu from those, very stable and good filtering, high current demand.

http://www.youtube.com/watch?v=YZ2_4_qYTNw

You will need at least 15VDC for the 7812 regulators, you can build one like this

http://www.google.co.uk/imgres?q=12...w=198&start=0&ndsp=15&ved=1t:429,r:2,s:0,i:77

 

When I operate mobile I do NOT use the car's electrical system. I use a pair of deep-cycle marine batteries that give about 12 hrs each on a 100W HF Transceiver (IC-706). There are several advantages to this method:

1. Noise is greatly reduced
2. There is little chance of having to go home barefoot

Additionally a 7812 requires a volt or two of headroom. The nominal output of my shack supply is 13.8V and the radio will work down to 11.7 volts. In a TO-220 package a 7812 is good for an Amp or an Amp and a half. You could run QRP I suppose but why limit yourself.

Edit: My mistake you did say "portable receiver" so the deep cycle marine battery might last a week on receive only.

 

Have you got an old ATX power supply that still works, you can make a good psu from those, very stable and good filtering.

They require input from the AC mains, unless I missed something.

 

As I understand it. It is car battery charger he want to use. They are often made out of a transformer and a rectifier. If it is one of those connect to a around 2200uF to 4700uF 25 volt electrolyte cap . Note the electrolyte polarity. Then measure voltage. I think you will se around 16 to 18 volt. And that should be enough headroom for the regulator. Note the regulator will need a cooling finn.

 

Sorry for the misunderstanding: I need a 12V power supply for my ham-receiver in the car, not a car battery charger. Papabravo got it right.
@papabravo: you are surely right using extra batteries, but I would still try to build myself a charger. My "ham-receiver" is a Stabo XR2001 scanner, which probably don't need a lot of power and I will have anyway the 4 AA accumulators allways in the device. I just want to charge the AA-s during the portable use of the scanner, or at least to avoid discharging.

 

Sorry for the misunderstanding: I need a 12V power supply for my ham-receiver in the car, not a car battery charger. Papabravo got it right.
@papabravo: you are surely right using extra batteries, but I would still try to build myself a charger. My "ham-receiver" is a Stabo XR2001 scanner, which probably don't need a lot of power and I will have anyway the 4 AA accumulators allways in the device. I just want to charge the AA-s during the portable use of the scanner, or at least to avoid discharging.

Just get a plug for the cigarette lighter and build your regulator on it, if you have extra voltage available. You could also google "Low Droput Regulator" and drop the headroom requirement to 0.2-0.3 volts. The alternator load dump is the thing that will kill your circuit so google "load dump protection".

 

Thanks a lot, papabravo, this is the information I was looking for. Thank you for the tipps, I'll do a little bit "research" now