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crgwbr
07-19-2006, 12:35 AM
Hello All,

I'm biulding a BS2 powered robot, as part of the motor controllers, I need a way the raise a voltage from 8.4 V, to 12 or 15 V.· Is this possible, or do I need· a seperate battery.· If it is possible, please explane.· Thanks!

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aalegado
07-19-2006, 01:23 AM
You could use a "DC-DC Converter" to raise the voltage you have to the voltage you need. However, there is no such thing as a free lunch and you don't get the increased voltage for free: A perfect conversion (i.e. no loss) would give you increased voltage at the output but at lower current than what is supplied at the input. But the conversion is always lossy so if you want a fair amount of output current you'll need significant input current.

You can find DC-DC Converter modules that can provide large output currents but they will cost more in $$$ and require higher-capacity batteries in your low-voltage power source since the converters will draw more current. A DC-DC Converter with a 10W capacity runs about $30-$40 in single item quantity.

In your application weight will be a factor so you have to decide if having two batteries (one for logic and one for motors) is more efficient than having one larger, higher-capacity battery and a DC-DC Converter to power your motors.

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I wouldn't connect that if I were you...

Vive Le Tour!
July 1 - July 23

Post Edited (aalegado) : 7/18/2006 6:30:24 PM GMT

crgwbr
07-19-2006, 01:25 AM
I only need a really small current, 10-20 mA. Just enogh to turn on a mosfet. I need the higher voltage so that I get a little resistance from the mosfet a possible.

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NerdMaster
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Mike Green
07-19-2006, 01:29 AM
Here's a small 2-6V to 12V switching converter that may still be available as a kit. It's easy enough to duplicate yourself.

aalegado
07-19-2006, 01:33 AM
crgwbr said...
I only need a really small current, 10-20 mA. Just enogh to turn on a mosfet. I need the higher voltage so that I get a little resistance from the mosfet a possible.


Jameco #216830CK. 1W capacity. Output of 12V@84mA from an input of 4.5-5.5V (around 200mA). $11. http://forums.parallax.com/images/smilies/tongue.gif

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I wouldn't connect that if I were you...

Vive Le Tour!
July 1 - July 23

stamptrol
07-19-2006, 01:40 AM
Or, use a mosfet like an IRL520 which will turn on quite nicely with only 5 volts on the gate. They are good for 10 amps or so and can be parallelled.

Cheers

crgwbr
07-19-2006, 01:45 AM
Thanks

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NerdMaster
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Life