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12v to 9v
greggors84 - 11/4/06 at 12:06 AM

Whats the best way to convert 12v dc to 9v dc.

Basically i want to use a little on board camera in the car, its powered off a PP3 battery, the camera specs are 9V 0.1A 1.2W, could i power this straight off the car battery, so i could leave it on and save me from changing the little battery.

Also, this wouldnt drain the car battery too quick would it?

Thanks

[Edited on 11/4/2006 by greggors84]

jambo - 11/4/06 at 12:37 AM

you could use the supplied mains charger with a 12v to 240 inverter
would also be handy for other small load devices

greggors84 - 11/4/06 at 12:42 AM

240v inverter would get a bit hot running all the time wouldnt it?

I just wanted something small and cheap. And i probably wouldnt be running too many 240v devices out of the locost.

greggors84 - 11/4/06 at 12:54 AM

Just though, when the car is running, the voltage across the terminals will be more like 14v, will this make much difference.

Found this also;

http://cgi.ebay.co.uk/3V-4-5V-6V-7-5V-9V-12V-DC-800mA-DC-DC-Car-Converter_W0QQitemZ9709488839QQcategoryZ96942QQssPageNameZWD10VQQrdZ1QQcmdZViewIt em

Im guessing this is what i need. Are they complicated? Not something that can be knocked up with a few components?

Thanks

[Edited on 11/4/2006 by greggors84]

Fatgadget - 11/4/06 at 01:03 AM

Maplin



Rated at 1000ma.Adjustable voltage. £8.99

[Edited on 11/4/06 by Fatgadget]

nitram38 - 11/4/06 at 05:14 AM

I use the maplin adapter on a colour bullet cam with no problems.
If you have a 200Amh car battery, your cam will last approx 2000 hrs! (minus a few losses)

[Edited on 11/4/2006 by nitram38]

[Edited on 11/4/2006 by nitram38]

rusty - 11/4/06 at 07:17 AM

If you dont mind doing a bit of soldering just get a voltage regulater IX i think part number is 7809 for the 1A or a 7809S for a 2A.

02GF74 - 11/4/06 at 07:43 AM

as rusty says, 7809; you could make the whoe thing for about £3 and wire it to the igntion. that way you will not drain the battery should you leave the camera in there all the time.

greggors84 - 11/4/06 at 11:35 AM

The input voltage for the 7809 is stated as 35v, does this matter?

Also is it as simple as soldering this into a switched ignition feed then onto the camera?

Sorry i dont have much knowledge on these components!

DarrenW - 11/4/06 at 12:01 PM

i think id just go with the Maplin idea - sounds very cheap and easy. A 12V accessory plug would be useful for other things as well.

02GF74 - 11/4/06 at 01:17 PM

quote:
Originally posted by greggors84
The input voltage for the 7809 is stated as 35v, does this matter?

Also is it as simple as soldering this into a switched ignition feed then onto the camera?

Sorry i dont have much knowledge on these components!


I haven't at the data sheet for this but know it is a 3 pin device; volts in, common i.e. 0V and output at 9 V.

the voltage you query sound like maximium inpiut; typically you need a couple of volts more on the input than the requlated out put so slapping your car battery on the input is fine. (12-15V approx)

It may to have capacitors across the input and output so that any spikes are absorbed....

if you are having to ask this typoe of question and say you don't know much about these things, do as Darren ^^^ says - how much would it be if you f*cked up your camera with some incorrectly made circuit? (I'd offer to make you the circuit but wouldn't want to be liable for effing your camera.)

greggors84 - 11/4/06 at 05:10 PM

Yeah i just liked the idea of the compactness of it! I will just buy a cigarette lighter socket and wire that in then hide it all under the dash.

Cheers for the info.

Bob C - 12/4/06 at 07:20 PM

Bear in mind that most wehicle electronics is rated to deal with a 44V transient for when the battery is unplugged when the alternator is recharging it at full chat, this is the "load dump" scenario. So a 35V rated part might just turn up its toes if you were daft enough to uncouple the battery with the engine running. Sounds like a daft thing to do but happens a lot when your car won't start so you borrow a mate's battery to start it, then put your own back on - or if you have a big red battery isolator switch.
I agree with the 7809 though - for 0.1A you wouldn't need a heatsink. Better might be an LDO (low drop- out) part - then you could feed it through a 10ohm resistor to protect against load-dump. Better still, I'll try & dig up an automotive rated part number tomorrow if I remember (there are stacks of these things)
Bob

Krismc - 12/4/06 at 08:04 PM

sorry to hijack...... but what is the best setup for a small camera, what camera? recorder? etc

wilkingj - 13/4/06 at 08:24 AM

quote:
Originally posted by greggors84
The input voltage for the 7809 is stated as 35v, does this matter?

Sorry i dont have much knowledge on these components!


35 Volts is the Maximum input voltage for the device. It will work fine on 12 volts.

If you are drawing more than 200ma, then make sure you bolt it to a decent heatsink. The 1Amp Max of the device needs a decent heatsink, its not obvious but it does.