Little help please!

[stuee]

Ok this might be a stupid question but we all start somewhere.
Im making a power supply for my car to power my uniden cb. details below
Uniden UH040XR/UH042XR/UH044 handheld UHF CB radios
24/12 Volt
Output voltage: 7.0 VDC
Output current: 70mA

ok, the unit only needs 70mA, i was going to use the lm2675 stepdown regulator. The question is, its 1A so will that make any difference. or will the CB only draw what it needs ie 70mA.
Its to run the internal battery charger for it.

Another question is, i have a few things for the car i want to make a multi power supply for, Is there anything i can use that will go from roughly 1v to 24v and about 10A. my idea is to make a small box with a rotory switch on it, then put it to what i select. ie laptop, bettery charger, bla, bla
Thanks

 

[ante1]

Stuee,

As long as the voltage is correct and the available current is higher than what you need it

 

[audioguru2]

Hi Stuee,
If the radio has charging circuitry built-in, it will draw only what it needs, 70mA. But the current could triple or more if the radio is in operation while charging its battery.
You don't need an expensive, complicated switching regulator for only 70mA. An inexpensive LM317T linear adjustable regulator will work fine from a car battery and won't even need a heatsink, unless you operate the radio while charging.

You must make certain if your radios have charging circuitry built-in. Usually that circuitry is in the charger. If you connect 7V directly to the radio's battery, it might blow-up! If the battery is Lithium, it might catch fire!

To get 1V to 24V at 10A from a car battery, you need a complicated and expensive buck-boost switching converter circuit.

 

[ante1]

Stuee, Audioguru,

Many handhelds both scanners and two way radios have there charger circuit built in but some of them also have different input connectors for power and charge. There is another inexpensive regulator the LM7807 that should be considered here as an alternative.

 

[audioguru2]

Yes Ante,
I agree that separate chargers are best. Murphy's Law says, Ka-boom, oops the switch was in the wrong position!

7807? I've read about them, never seen one.

[move];D ;D ;D[/move]

My first happy face had too much to drink.

 

[ante1]

Hi Audioguru,

There is not always a switch just two sockets on the side of the apparatus, it all comes down to the human factor here. 8) So, you are looking down the barrel of a bottle today? Well I hope your face is still happy anyway. ;D ;D Since you haven't seen any, I can tell you the 7807 looks just like the rest of the family. ;D ;D