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ethereon
Joined: 26 Feb 2006
Posts: 3
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 15 Jan 2009 3:15 Bipolar power supply out of a regular power supply? |
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Hi,
I have the following problem : I have a triple output DC power supply (Agilent E3631) : +6V, +25V and -25V. I need to construct something that will enable me to have -12V to +12V across two terminals. The current requirement is about 7 A (driving a heavy motor).
What would be the best way to go achieve this? Any suggestions are greatly appreciated.
Thanks!
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IanP
Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast
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15 Jan 2009 3:43 Re: Bipolar power supply out of a regular power supply? |
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One option is to create so called "virtual ground" ..
If your power supply can deliver 25V @ 7A then:
you will need two power transitors (1xNPN and 1xPNP, Darlingtons) mounted on a heatsink, and here is explenation on how it can be done:
http://tangentsoft.net/elec/vgrounds.html
for higher currents reduce the emitter resistors (R3 and R4) to 0.1Ω or less ..
Rgds,
IanP
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Mr.Cool
Joined: 20 Jun 2001
Posts: 641
Helped: 24
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15 Jan 2009 4:40 Bipolar power supply out of a regular power supply? |
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is this a DC motor? i have had similar problem before and i just put 24V across DC motor terminal - though it was only a 12V motor. it spins twice as fast.
yes motor is not rated for this so excersize care
Mr.Cool
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ethereon
Joined: 26 Feb 2006
Posts: 3
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15 Jan 2009 5:10 Re: Bipolar power supply out of a regular power supply? |
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IanP : Thanks. That might just be what I need. I'll check it out.
Mr. Cool: Yes, it's a DC motor. The issue is that I need to alternate the direction of rotation at a certain frequency. Since I can program the power supply, I thought the easiest way is if I could figure out a bipolar power mechanism.
Optionally, if there was something akin to a "high-voltage multiplexer", where I could select which terminal output to select (-ve or +ve).
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IanP
Joined: 05 Oct 2004
Posts: 6490
Helped: 1542
Location: West Coast
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15 Jan 2009 6:26 Re: Bipolar power supply out of a regular power supply? |
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For changing direction you can employ the H-Bridge configuration ..
Here is an example:
http://www.cadvision.com/blanchas/hexfet/np-s.htm
In this circuit, the supply voltage can be 24V (and more, with Z1 removed) ..
Rgds,
IanP
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