How to drop 12v to 1.5v?

[Waorani]

I'm trying to integrate a 1.5v sonde unit into a video camera system for inspecting animal burrows. I've got 12v going to the camera and would like to pull 1.5v off that to power the sonde. Looking for simplicity, dependability and small size. Options/suggestions?

 

[e9999]

well, seems like you have a choice between just resistors in series type system if power and power dissipation are no object or go from 12VDC to AC back to 1.5V DC which would be considerably more complicated. There may also be some easy way of doing this with IC or transistors and what not, but I don't know about that.


Anyway, how about a 1.5V battery?

 

[Waorani]

Sonde runs on 1.5v AAA battery but will be enclosed within a camera head and unaccessible in routine use. I could run a separate set of wires for the sonde to a 1.5v battery but was trying to avoid hassles that will create and just pull off the 12v DC going to the camera.

I've found a 12v to 1.5v cigarette lighter plug adaptor that I might be able to take apart and use the circuit but was hoping there might be an easier solution.

 

[Bret]

12V DC to 1.5V DC needed

Might try here. Will have to do a little figuring on load though.

 

[rusty_tlc]

The LM317 is a three terminal voltage regulator that has been around forever. It is simple to implement and very robust

LM317 <------data sheet and application notes are at this link.

Most radio shack stores will carry everything you need to build a simple regulator circuit. If you don't have a radio Shack nearby DIGIKEY sells stuff retail in small quantity's.

 

[rusty_tlc]

I had a minute to run the numbers.
Use 240 for R1 and 47 for R2
That will give an output of 1.49 Volts (48 ohms would be exactly 1.5 but 47 is the closest standard value.) If you feel you absolutely must have exactly 1.5V use 56 ohms for R2 and put a 5K potentiometer in parallel to trim the output to exactly 1.5V.

 

[FJ40_owner]

well, seems like you have a choice between just resistors in series type system if power and power dissipation are no object or go from 12VDC to AC back to 1.5V DC which would be considerably more complicated. There may also be some easy way of doing this with IC or transistors and what not, but I don't know about that.


Anyway, how about a 1.5V battery?

Are you serious?

Why not a LM series voltage regulator? Simple

 

[FJ40_owner]

I had a minute to run the numbers.
Use 240 for R1 and 47 for R2
That will give an output of 1.49 Volts (48 ohms would be exactly 1.5 but 47 is the closest standard value.) If you feel you absolutely must have exactly 1.5V use 56 ohms for R2 and put a 5K potentiometer in parallel to trim the output to exactly 1.5V.

Ah yep. I would use one watt resistors and call it good.

 

[Waorani]

Thanks guys. I did some searching after the initial LM317 suggestion and that looks simple enough. And now I don't even have to do the math!

 

[rusty_tlc]

Ah yep. I would use one watt resistors and call it good.

The current in the feed back loop should be pretty small, 1/4 W resistors would do. I suspect the device he is powering has pretty small current requirements, it normally runs on a single 1.5 V AAA battery. A TO-220 shouldn't even need a heat sink.

 

[rusty_tlc]

I found this today when I was looking for something else.

It could help


1Amp power supply kit $10.99

 

[Waorani]

Thanks again. I did pick up a couple of LM317s and the resistors you calculated but I'll grab a couple of these to play with as well. Plus another parts site I can poke around on and find stuff I didn't know I needed!