Voltage reduction

[rc_farmer]

I want to build/buy a device that you can input a higher capacity voltage and have outputs of different voltages:


***************output------ 9.6
EX: input 18.5v----
**************output ------7.4

I am not an electrical engineer......so this is a challenge to all you engineers out there. Is this possible?

[Brian in PA]

Rob I think that a rheostat or potentiometer would to the job. They have a good selection of these at Radio Shack. Both of these devices are variable resistors.

Brian

[Espeefan]

Rob, any idea how much current capacity the device needs to have? Pots and rheostats are definitely an option, and cheap too, but not quite as efficient as say a DC switching regulator. As Brain said, both pots and rheostats are a type of variable resistor, and because of that they reduce the outout voltage and waste it in the form of heat. A switching regulator, on the other hand is much more efficient. Sometimes up to 80 or 95% efficient. Energy is not wasted in the form of heat as much as a resistor.

Here is a 3 amp switching regulator. This one can step up or step down the input voltage.

http://www.dimensionengineering.com/anyvolt3.htm

Here is a 2 amp switching regulator, step down only.

http://www.dimensionengineering.com/DE-SWADJ3.htm

Finally a 1 amp.

http://www.dimensionengineering.com/DE-SWADJ.htm

Depending on the load you expect the regulator to drive, these may or may not work for you at all. 3 amps is not going to run a 540 motor under a load, but 3 amps could run some other small devices.

For some more serious switching regulators, Castle Creations has external BEC switching regulators.

20 amps.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXYCA6&P=ML

10 amps.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXSWL3&P=ML

I am sure if you searched the web, you could find more switching regulators, but you would need one regulator for each desired voltage drop. In your example, you would need two regulators. One for the 9.6 volts output and one for the 7.4 volt output. Hope this helps.

[rc_farmer]

Thanks guys, I will sort thru these and determine what options to use. I am trying to to eliminated using two different battery packs in my Gator. My hydro pump is 12v and the MFU, of course is 7.4. If I thought the MFU wouldn't fry with 13v running thru it......I would just run one pack for both. I have run a medium-charged 12v thru it or about 5 minutes, but under no load and not on a fully charged pack. Too much money to cook! Tamiya said that 7.4 was the max, but i do know that it will handle almost 11v.


Thanks

[Espeefan]

Rob, I think your best bet would be the 20 amp Castle regulator. 20 amps should be enough to handle powering the MFU and the main drive motor. As long as you are smooth with the throttle, I don't think a 540 sized motor would pull 20 amps, unless it was under a serious load. A 540 can motor can pull more then 20 amps in the right situation, so if you don't think the regulator can handle the current draw, I would suggest this. Replace your hydraulic pump motor with a 7.2 volt motor, that will run the same RPM as your current 12 volt motor. Figure out what RPM you need to keep the pump speed the same and choose a lower turn 540 motor to keep the speed up. I think it would be easier to swap the motors then to bother with a regulator. A good 540 motor won't cost you anymore then a 20 amp regulator. The only thing to be concerned with is the bolt pattern of the current motor vs that of a new 540 motor. Sometimes the Germans have some odd patterns. An adapter plate might be necessary, and maybe a longer shaft coupler of some kind.

[Blender]

If you want to switch the motors the leimbach pumps use a standard M3 screws with 25mm spacing. the stock motor has an eighth inch shaft, but it's a little shorter than the standard motor shaft. that's easy to fix though. I've been experimenting with different motors on my pump over the last week. I'm now using a very tiny brushless outrunner.

espeefan's switching regulators would also work just fine.