RC-Monster Forums - View Single Post

BrianG · 12:33 PM

I suppose you could, but it would be kinda clunky, not to mention $$$. The LED thing could be done, but it's not "active protection" (meaning: it still relies on the user to notice something and stop running). I still think an overvoltage switch is the best idea since it would disconnect if it saw anything over a certain voltage.

I drew up the idea I was thinking of:

U1 is pretty much any Op-Amp that can work off a single supply as low as 5v and as high as ~30v (for if the BEC sends full v). The LM324 looks like a decent candidate.
D1 is a Zener diode to set the trip reference voltage.
R1/R2 is a voltage divider to fine tune the "trip" point in case the zener diode is not a perfect match.
Q1 is a PNO transistor set up as a switch. Power lost should be very minimal so no heatsink is needed.
R4 limits Q1's base current.

Since the output current will be limited by the op-amps output X Q1's hfe, you'll probably need a darlington pair. A single transistor that can handle ~10A usually does not have high current gain.

All these parts can be obtained at RadioShack for around $10-$15 at a guess.

	(#6)
BrianG RC-Monster Admin Offline Posts: 14,609 Join Date: Nov 2005 Location: Des Moines, IA	05.31.2008, 12:25 PM I suppose you could, but it would be kinda clunky, not to mention $$$. The LED thing could be done, but it's not "active protection" (meaning: it still relies on the user to notice something and stop running). I still think an overvoltage switch is the best idea since it would disconnect if it saw anything over a certain voltage. I drew up the idea I was thinking of: U1 is pretty much any Op-Amp that can work off a single supply as low as 5v and as high as ~30v (for if the BEC sends full v). The LM324 looks like a decent candidate. D1 is a Zener diode to set the trip reference voltage. R1/R2 is a voltage divider to fine tune the "trip" point in case the zener diode is not a perfect match. Q1 is a PNO transistor set up as a switch. Power lost should be very minimal so no heatsink is needed. R4 limits Q1's base current. Since the output current will be limited by the op-amps output X Q1's hfe, you'll probably need a darlington pair. A single transistor that can handle ~10A usually does not have high current gain. All these parts can be obtained at RadioShack for around $10-$15 at a guess. Last edited by BrianG; 05.31.2008 at 12:33 PM.