752 RC switch question - wiring diagram?


This should be dead simple, but I can’t seem to get things to come to life…

I’m using a 752 R/C switch to–hopefully–turn on an LED headlight. I’ve got the board plugged into the receiver (and the receiver turned on), and nada. zippo. No signs of life. The onboard LED doesn’t blink, come on full, nuttin’!

Here’s how I have it wired…

Ground - black wire to ground on the receiver. (Spektrum 2.4 gHz 6-channel rx)
VRC - red wire to +5v on the receiver
IN - white wire to signal

On the output side, I’ve got an LED and 1K-ohm resistor going between “Out” and “Ground.”

Alas, Google has failed me. I’ve found one reference on one forum that mentions using this board for what I want to do (and it works well for that guy), but that’s it. It should bear mentioning that on his example, he’s got the +5 going to “IN” and the R/C signal going to VRC on the 752. (I tried that, too, with identical results.) I bought 5 of these boards, and have tried 4 of the 5, all behave the same.

So, the simple question–what am I doing wrong???



Call off the dogs. Once I bridged the VRC and VCC pads, things sprang to life and worked as advertised. (phew!) Bugger that I had to look on the MOSFET version of this board to see an actual wiring diagram that illustrated things, but now I know, and now folks who are searching these forums for “752” have another thread that might help them out.

For the record, “IN” is the signal coming from the receiver (white or yellow wire), and VRC is the +5 volts (red wire). The fellow on that other forum I think must have had his wires crossed when typing.)

Now back to the workshop to finish the wiring. Good times!



Curious behavior…

My thought was to daisy-chain two 752s, such that the first acted like a master switch controlling all the lights, and a second one would come on and off in relation to the position of the stick. It would seem logical–using the output of the first as the V+ to the second. Except for one minor little problem. When you turn on the power at first, everything’s kosher. If the lights are “off,” then the second board doesn’t get any power and all lights are out. However, the moment you turn the lights on, then the first board continues to feed power to the second board regardless of the signal coming into it. The on-board LED is flashing (indicating Low), but the output is still High.

Here’s essentially how it’s wired:

Board 1:

IN (channel 5 signal) OUT (wire to VRC on 2nd board and LED positive lead)
VRC (+5v)
Ground (ground) Ground (wire to Ground on 2nd board and 1K ohm resistor to negative lead on LED)

Board 2:

IN (Channel 3 signal) OUT (LED positive lead)
VRC (OUT from board 1)
Ground (Ground from board 1) Ground (1K ohm resistor to negative lead on LED)

Logic tells me this should work, but is there some weird feedback loop coming from the channel 3 in that’s backfeeding VRC? I haven’t a clue. For now, I’ve separated the two boards from each other, so I can turn the one light on with Channel 5, and the second one on with channel 3. I cannot use channel 5 to turn off the channel 3 light as I had hoped I could.




Hello, k.

I don’t understand why your system was behaving like that, but it is kind of unusual to power a Board 2 from the digital output on Board 1.

To get the effect you wanted, you could connect the boards independently and then connect both outputs to an AND gate. The output of the AND gate could power some LEDs.