12v to 9v converter

Discodog

I have a little portable pir alarm that runs off a 9volt pp3 battery.
I would like to put it in a vehicle. Would a converter like this be ok to power it from the vehicle battery?

http://item.mobileweb.ebay.co.uk/viewitem?sbk=1&nav=SEARCH&itemId=300661988628

humbert

Yeah, I'd assume an alarm would draw far less than three amps. On first use just check it from time to time to make sure it's not getting hot (the regulator that is).

Discodog

Thanks. What's the likely drain on the car battery? I want to be sure that I can leave it on overnight.

humbert

Discodog wrote: »

Thanks. What's the likely drain on the car battery? I want to be sure that I can leave it on overnight.

Whatever it says on the alarm really. The voltage regulator shouldn't have an appreciable effect. Then compare that to the capacity of the car battery.

I'd be amazed if it was likely to be a problem but better to check.

Discodog

It runs for a week on one battery so the draw must be minimal. Thanks for the advice.

whizbang

Some of these regulators are extremely noisy (electrically speaking), also may not be able to regulate properly at the very low current you are going to be using. If possible, try to get a linear regulator, as the alarm may be sensitive to the quality of the power supply.

It would be a good opportunity to use a NiCd rechargeable battery also.

satstheway

Used a similar reg to run a electric fencer for a farm. It has no noise and worksas expected