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Robot with Various voltage requirements

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Robot with Various voltage requirements

By osfreak
-  Sat Dec 08, 2012 10:22 pm #152980
Hello everyone!
I have a question about a robot I am currently in the design stage on. I have been monitoring the voltage requirements of the components I will be using and the amperes of each item. Currently, the project is going to require 3 seperate batteries, 6v, 9v, and 12v. The highest amperes needed are from the Sabertooth motor driver, 2x5 RC, requiring 5A continuous per channel, 10A peak. I was wondering if anyone has a suggestion, or schematic from a previous build, to create a board to supply each of the voltages from a single battery? I need to run a single 24v battery because of weight and space requirements.

My idea is to have either a 14.8, 18, or 24 volt battery which will then run through this board and supply 12v 10A (for the Sabertooth), 9v for both Lynxmotion's Botboarduino and the SSC-32 (Both would need 35-50mA each), and 6v to run all the servos (Hitec servos - 3x HS-422, 3x HS-485HB, & 8x HS-645MG). I figured I would be safe with 12v 10A, 9v 1A, and 6v 5A.

So far, I have this in mind for the curcuit:
LM7809 for 9v (Mouser # 512-LM7809CT)
LM338T for 6v (Mouser # 926-LM338T/NOPB)
LM3150 for 12v 10A (Mouser # 926-LM338T/NOPB)

My only unknown is the LM3150. I personally have never used this chip. Is there another chip anyone would recommend to step-down the 24v to 12v 10A? Better yet, is there a different circuit anyone would recommend over this entirely? Any help, suggestions, tips would be greatly appreciated! If anyone needs any other information or has questions about my circuit I'll be more than happy to answer. I'm really trying to get this circuit built fairly quickly to have it tested prior to installation.


Thank you! :D

Re: Robot with Various voltage requirements

By Duane Degn
-  Mon Dec 10, 2012 5:47 am #153038
Do you have a reason for the battery voltages you listed?

The Sabertooth runs fine on a three cell LiPo. I'd think that would be my battery of choice.
I worry about the 6V regulator. It's a linear regulator and will get very hot. With that many servos, you'd be better off with a switching regulator (they're more expensive but your batteries will last a lot longer).

I don't think you need the 9V regulator at all. The Lynxmotion board will run fine off the 6V line.

I'd worry about the 12V regulator you chose since you mentioned not having used it before. Switching regulator often require external inductors and capacitors to work correctly (or at all). I don't think make your own switching regulator in a trivial matter. You might want to spend the money for a ready made unit (again, these will be a bit expensive).

If you use a 12V (like a three cell LiPo) you wont need to regulate it at all for the 12V line.
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