Hi all,
I have on of those power supply, and I want to use it for powering a small amp and fm radio. The rated output is 12V DC 1.3A.
The power supply is suitable for the amp, but probably not for the radio, as this circuit is designed for a 9V battery. My need is to drop the voltage to 9V and also to drop the current because the radio only draws 8 mA, and feeding the circuit with a 1.3A would probably damage it.
What is the best way to have 9V 8mA from my power supply?
Thanks, Ralf
I have on of those power supply, and I want to use it for powering a small amp and fm radio. The rated output is 12V DC 1.3A.
The power supply is suitable for the amp, but probably not for the radio, as this circuit is designed for a 9V battery. My need is to drop the voltage to 9V and also to drop the current because the radio only draws 8 mA, and feeding the circuit with a 1.3A would probably damage it.
What is the best way to have 9V 8mA from my power supply?
Thanks, Ralf
Pretty simple circuit 
Something like this: Portable CD Player Adapter For Car
Don't worry about dropping the current...the load will draw the current it needs.
Something like this: Portable CD Player Adapter For Car
Don't worry about dropping the current...the load will draw the current it needs.
Oh, sorry, I have skipped some points reading your post...
Also, you can simply connect a 3.3V Zener Diode between 12V power supply and your radio, to get approx 9V
This will be about 8.7V, but this should be ok...
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you can run the little power amp directly after the rectifier of the 12Vac 1.3Aac supply.
The DC voltage after rectification and smoothing will be about 16Vdc to 18Vdc.
If you really meant 12Vdc then run the amp direct off that supply.
From the same supply attach a lm7809 to give your 9V for the radio receiver. Download the datasheet for the lm7809 and follow the advice accurately.
The DC voltage after rectification and smoothing will be about 16Vdc to 18Vdc.
If you really meant 12Vdc then run the amp direct off that supply.
From the same supply attach a lm7809 to give your 9V for the radio receiver. Download the datasheet for the lm7809 and follow the advice accurately.
Mmm, never used a zener, how do I connect it?
Will this one be good (zener from rs-components)?
Anyway, it will cost me less to use a L7809, if I only need the 2 non polarized caps depicted in the datasheet (0.1 and 0.33 uF), because I already have them.
Regarding the current drop, anybody knows for sure that my supply won't do any harm to the radio circuit based on a TDA7000, that needs only 8mA?
Thanks, Ralf
Will this one be good (zener from rs-components)?
Anyway, it will cost me less to use a L7809, if I only need the 2 non polarized caps depicted in the datasheet (0.1 and 0.33 uF), because I already have them.
Regarding the current drop, anybody knows for sure that my supply won't do any harm to the radio circuit based on a TDA7000, that needs only 8mA?
Thanks, Ralf
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