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I have a servo from an rc car with 6 wires, it turns out the servo controller is built into the RC Car with a bad board. I have a motor, a gear box and a 10k pot attached to it. I'm trying to build a modified H-Bridge with an opamp. For my circuit I need negative voltage. My question is if I use the output of a 5V Regulator as Gnd, the source anode as + Voltage, would the source anode then be usable as - voltage. My idea is that I could take my battery source of 10v, use a 5v regulator and have postive 5v, negative 5v and gnd. Feed the negative and positive into a pwm controlled opamp, connected to a half h bridge and finally powering the tiny dc motor. I also think maybe I should add a diode to the motor to prevent negative voltage coming back across the circuit. Schematic

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Not a good idea to do that with linear regulators - they are not push-pull outputs and if you attached a motor between the regulated output and the positive feed to the regulator, the regulator won't regulate any more.

What you are trying to build is a half bridge and if you want some kind of "neutral" mid rail for the motor return wire then use exactly the same circuit you have shown but biased to produce half the battery voltage.

But, then you have a H bridge in all but name so, why not just use a H bridge and avoid wasting heat in the "neutral" connection (or linear regulator should you find one that has a push-pull output).

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  • \$\begingroup\$ Thank you, I've thought about using a full H-Bridge it would certainly make things easier, and I have plenty of transistors. The only reason I'm looking for an alternative to the standard h bridge is that the gearbox is attached to a pot and this setup is just a servo without the control electronics. I want to be able to easily control the position of the servo. \$\endgroup\$ – Cfoote7 Mar 22 '15 at 17:33

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