Reducing voltage from 12V to 1.5V

[Blue4Ice]

I am in the process of installing the temp monitor as posted by gtech a while back (the one from maplin). However I dont want to run it off a seperate battery but from the MR2 battery so that I can put power on a switch, and never have to worry about the battery running our, or drawing attention to the screen when parked up.

Anyway the current power requirement of the temp module is 1.5V from an AA battery. Does anyone know what I need to run it straight from 12v? I see there is a circuit in the knowledgebase under the CC temp monitor but this is for 5V. Can this still be used for 1.5V or will it damage the module?

Thanks

[Gordy]

That's a big drop. The problem is dissipating the heat from whichever device you choose to use to drop the voltage.

The first thing that you need to know is the current draw (load in amps) of the device so you can choose the right bits to use. As it's nominally a battery powered device it's likely to be low, in the region of milliamps.

It's many years since I have done any analogue electronics design, so I do not know if a chip is available to do exactly what you want. I doubt it though. If not then you are going to need a 5V voltage regulator plus potential divider to get you safely down to 1.5 Volts, and that is not something that I can easily describe here. It's also not something that you can knock up in five minutes unless you know what you are doing.

Best to use a battery and switch matey! You could always use a relay driven from the ignition instead of a switch to connect the battery power if you wanted auto turn on / off.

[Blue4Ice]

Thanks for that Gordy.

There do appear to be some products available to drop from 12V down to 1.5V but not too sure how important input voltage is (as the car is closer to 14.4V when on). I may just buy one and see how it goes. However I dont want a fire behind the dash lol

http://www.eurobatteries.com/sitepages/ ... -dc-dc.asp
Top one

[Gordy]

I never knew they made them. Good. That should work.

(Don't worry about the 14+ Volts because it's completely normal, and battery voltages are nominal anyway. You need more than 12V to charge 12V. Also, when you turn off the charging circuit the battery voltage will float around a bit anyway).

[paul port]

Well you may as well buy one from Maplin, L17AR £4.99 on special offer at the moment

Paul

[ben laden]

you could use an in line resirtor as used to lower the voltage for led's to be used. these can be bought off ebay for next to nothing.

Ben

[Gordy]

you could use an in line resirtor as used to lower the voltage for led's to be used. these can be bought off ebay for next to nothing.

LEDs need resistors to limit the current. It's totally different. Do not do this.