12v converted to 6volts. how to do?

lets say we have a mobile electronic product that uses 6volts from a cig lighter plug that id like to hardwire. im sure there is a resistor in the cig plug. how do i put a resistor inline to drop the volts?

-------------
owner of
Motion Marine & Car Audio
the florida keys

What kinda current draw is the load device going to be drawing? This will need to be determined before selecting a resistor because if you just pick a resistor you may end up burning it up by using it over its power rating.

Similar to the way speaker impedances work. If you have a 12V source, you will need a series resistor of the same value of the load (whatever you are powering).

When you have a series circuit, the voltage across each load will add up to the input voltage. Thus, if you have 3 resistors in series with a 12V source, they will drop a total of 12V. If you have 2 resistors, of the same value, each will drop equal voltage, thus 6V each. Therefore, if you select a resistor with the same impedance as your load, you will be able to drop 6V across your load.

WOW. ENOUGH SAID. I am working on a BS degree in Electrical Engineering. Actually working on designing a small 5-band EQ as a project for one of my classes this semister, how fun. Let me know if you have any other technical questions.

For quickest response, e-mail me @ drvnbysound@aol.com

-------------

Let  us know the current your device will need.You might be able to use a resistor and a zenner diode for a regulator.Or use a NTE 962 or 1962 3 terminal regulator ic(simple).Russ

-------------
BigDog

a mechanic friend of mine has a kit that will test the draw of the unit and determine the size resistor. i thought this subject would be fairly simple, but its very complex. i was thinking i could just solder a resistor inline with the power wire. i undestand i must use the right size resitor to make sure i have enough and no too much power. what does a simple resistor look like? where does one but them? blah blah blah...

-------------
owner of
Motion Marine & Car Audio
the florida keys

dudek38 wrote:

---

a mechanic friend of mine has a kit that will test the draw of the unit and determine the size resistor.

---

 Measure the draw of the unit with an ammeter then use Ohm's Law.

 Item draws 150ma.. needs 6 volts..

 Resistance = volts divided by amps

?=6/.150

R= 40 ohms

 To find wattage of the resistor, multiply amps times voltage..

Watts = 6 volts * .150 amps

Watts =  0.9 - use a 1 watt resistor.

 Personally, I'd just use an adjustable voltage regulator.. It depends on what the device is, but using a voltage divider circuit with resistors usually isn't the best way in terms of voltage regulation..

 For parts, I use Digikey, Jameco, JDR Microdevices, and when I need something right now, Radio Shack. Unfortunately, Rat Shack will be the most expensive, and the people behind the counter won't have a clue about electronic components.

 Regards,

 Jim

You can't use a voltage divider, because the resistance needed will change with the load hooked up. Use a regulator.

-------------
2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?

Yes, the regulator is the easiest way to do it. If you buy a three terminal fixed regulator, the most common being a 78xx with the xx being the desired fixed output voltage (and that's an industry standard number to cross reference) your installation is as simple and straight-forward as you can get. See the diagram below:



You can order this device pretty much any place they sell electronics components - should run about 4 dollars. The best part of this type of installation, is you need to do NO figuring, no math, no construction... it is a simple point to point device, with regulation. This means that whether you car is running or off (14.4/2 = 7.7 volts or a 28.3% OVERVOLTAGE if you use a simple voltage divider - BAAAAAD) and no matter what the load is (up to the safe operating load of the device) you will ALWAYS get just exactly 6 volts...

I would have thought a BS in Electronics would have known about simple three terminal fixed regulators... (jab - poke - jab)

-------------
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

Order from www.mouser.com btw, and if you need more than 1.5A, you can well, find a regulator that does support more, or you can put regs in parallel for (Current each will take) * (Amount of regulators)

-------------
2009 Pontiac G8 in planning stage
HU: ?
Speakers: ?
Amps: ?