How do I convert 12 VDC into 3 VDC?

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  #1  
Old 01-08-03, 06:33 AM
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rvitek
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How do I convert 12 VDC into 3 VDC?

I have a big big 12VDC battery that powers my starter for my RC car. Well, I want to use the same battery to power my glow ignighter, but the glow only takes 3 volts (anything more will blow the glow plug).

Can I create some type of resistor system to get a 3VDC current from the 12VDC battery?

Thanks!

Ry.

Attached is a picture of what I'm thinking, the box in the middle is what I want to build.

<img src="http://www.explorerforum.com/data/3059/9266drawing1.jpg">
 
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  #2  
Old 01-08-03, 07:13 AM
J
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I would suggest a voltage regulator circuit.
here is a link to one.
http://www.opamplabs.com/zenerreg.htm

This one is even better
http://www.mitedu.freeserve.co.uk/Ci...ower/lm317.htm
 
  #3  
Old 01-08-03, 07:25 AM
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You can, but you can go to Radio shack and buy a cheap voltage regulator (keep in mind the amperage requirements of the glow plug). You can also use a DCtoDC converter, but they are not cheap.
 
  #4  
Old 01-08-03, 07:41 AM
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brickeyee
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Post back the resistance of a cold glow plug and I will try and find a part number. The circuit might take 2 resistors and a three terminal voltage regulator. Digikey is the best part source.
 

Last edited by brickeyee; 01-08-03 at 10:20 AM.
  #5  
Old 01-08-03, 07:52 PM
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Digikey's a good supplier, but for these few parts, shipping will slaughter any cost savings over Rat Shack.

If you were building dozens of 'em, Digikey would be the way to go. For three parts, mail order's not worth the hassle.

IMHO, of course.
 
  #6  
Old 01-09-03, 07:47 AM
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brickeyee
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Problem with rat shack is that they no longer carry enough stuff to be at all usefull. This will probably take a big TO-3 regulator since over 9 volts will be dropped. At even 200 mA thats 1.8 watts and will quickly overheat a smaller package. While the 3 terminal regs have overheat protection built in, a design that will overheat and use it is a bad idea.
If the resistance comes back I will run the numbers and find the smallest part. A local electronic supply house would be my first suggestion normally, but they are getting to be few and far between.
 
  #7  
Old 01-09-03, 08:01 AM
J
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Here is alink to amodel air craft glow plug driver.
http://www.vision.net.au/~timotsc/plugdrvr.pdf

General glo info here
http://www.excelsiorweb.com/rcair/glowplug.asp
 
  #8  
Old 01-10-03, 04:43 AM
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If it takes less than an amp or so, you can buy a DC to DC convertor with a multi voltage selector for less than $15 at walmart.
 
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