Hi, I had a question if you guys could help, I want to convert the cars 12V source to 5 or 6Vs to power a small DC motor. What size resistor should i use? (OHMS) Thanks

 

Need more info. The voltage level in your car will fluctuate from about 11.3V when off to up to 14.5V when running. Do you not care the specific voltage level that it is dropped to? What current level is required?

 

http://focus.ti.com/docs/prod/folders/print/ref02.html

That can give you 5V +/- 150mV at a price of $4.07 from Digi-Key assuming you don't need more than 1.4mA.

Mike

 

1.4mA is the supply current, not output current, for that piece. Also, it's not even close to being suited for a motor application. Unless it's a pager motor, the moment it turns on you'll swamp the regulator.

Let's wait until we understand the application before suggesting components...

 

Sorry 21mA, I didn't read the spec sheet and tried to qualify it being for lower power apps. At any rate, cut me some slack... I think the chemicals the water damage recovery crew sprayed after this morning's flood in my apartment are getting to my head

 

This is a small 12V DC motor that only goes 5000RPMs. It probably has 1 or 2 watts going through it, Imagine a Servo on a RC car or an RC car motor spinning real slow. The cars 12V power spins the motor at its highest speed 5000RPM, I tested a 6volt power source to it which made it spin slower and that is what I want. Im guessing there is only 1 or 2 watts going through it. Is this enough info? Some tech shop told me I should get a resistor but he didnt know how many OHMs to get

 

Use a multimeter and measure the resistance of the winding... that will tell us how much current it pulls at 12V. Once we know the current, we can suggest appropriate values. Resistors will be the (slightly) cheaper method, but a voltage regulator will offer a constant speed.

 

Ok, I got some ratings off the small 12V DC motor im using:

Gearhead Motor
60 RPM, 12VDC @ 110mA

This spins to fats when I plug it straight up to my cars 12V power supply. I want it to spin slower, I tried hooking it up to a 6V battery and it did spin incredibily slow, which is what I wanted. So how would I get this motor to spin to the speed of 4 or 5Vs?