How to build a 12 volt to 1.5, Volt DC/DC Converter

Greetings all.  I suspect this is a pretty remedial question but I've not been able to find help or instructions online...so here I am. 

Basically I want to build my own 12V to 1.5V converter to power a small electronic device in may car that is currently chewing through a lot of batteries.  Such converters are cheaply available online but what would the fun of buying one be, if I could make my own instead?!  Can anyone help me get started by pointing me to an online resource with information on how to make such a device?

Many thanks


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mcbenney (author) 7 years ago
Durr... How'd I overlook that, I wonder?!

Yeah, I'd done the datasheet route... I just wasn't finding apples to apples to what was available at radioshack and I'm not conversant enough to know what technical differences are acceptable and what would be problematic. 

In any event I'll need to start at least with the right schematic. 

Back to google.
.  I hope you have a better source of components than Radio Shack - they just don't carry the number of hobbyist items that they used to.
.  With a lot of electrical/electronic parts having a higher voltage and/or current rating will not matter. Eg, if the schematic calls for a ¼W resistor, a ½W resistor is perfectly OK.
.  Sometime the letters in a component number will tell you such things as material used (Germanium, Silicon, &c), type of package (TO-252, TO-263, &c), &c. Codes vary a lot, so I can't make a blanket statement.
.  Sometime the numbers in the component number will tell you something. Eg, in the 78xx and 79xx series of voltage regulators, 78xx's are positive and 79xx's are negative. xx will indicate output voltage. So a 7809 is a +9V regulator.
mcbenney (author)  NachoMahma7 years ago
Ha.  I'm not a fan of Radio Shack either.  Generally the kids behind the counter know less than I do which is saying something. I used Radio Shack primarily to demonstrate the problem I was encountering.  I have a couple of other local options that probably offer better choices.  Then there's always the NET, I suppose.  Thanks again for your help.
mcbenney (author) 7 years ago
Thanks!
"Schematic" was the key word missing from my searches. \

Your tip led me to this page which seems to be what I want.   The set up appears to include a couple of resistors, a transistor and and zener diode.  My next question is how does one determine the which type of each component to get?  For example, at RadioShack, 10k resistors come in 1/8, 1/4 and 1/2 watt varieties.  The transmitters I found have dissipation ratings from 350mV to 80V. 

I realize I'm flaunting my ignorance.  Any help will be much appreciated.
.  Oops. I didn't notice at first, but the schematic you link to is for 12V to 9V, not the 12 to 1.5 you want.
.  To find the specifications for the zener, Google "BZX84B10" or "BZX84B10 +specs" or "BZX84B10 +datasheet". For the transistor, substitute BD139.
.  I'm not confident enough in my memory of circuit theory to try to answer how big the resistors need to be. Somebody else will probably speak up before long.
NachoMahma7 years ago
.  You'll have to wade through some trash, but the following Google search will get you what you want:
12 volt to 1.5 volt DC/DC converter +schematic