Can I use an Arduino GPIO pin HIGH to trigger an NPN transistor to short two wires on the ESC?
Both the ESC and Arduino are on the same ground... but will this only work if the ESC switch is pulling to ground? Otherwise am I stuck using a 5V relay to mechanically short the wires?
Right now my dilemma is that I have to manually turn on my ESCs and I want the Arduino to do with minimal bulkiness. Also this ESC won't arm with throttle commands.
I think that some information is required. Which Arduino board? A data sheet for the ESC. A schematic of the setup.
It will be easier to help you if you will read and follow the forum guidelines.
groundFungus:
I think that some information is required. Which Arduino board? A data sheet for the ESC. A schematic of the setup.
Can't find any datasheet, but I doodled a schematic...see attachment.
When the ESC is powered I know wire 2 rings to battery ground (but multimeter shows -126 instead of 1?). Maybe I should try to short wire 1 to battery ground to too see if it would turn on the esc?
Here is the ESC. See the remote with two wires. When you click the buttom it just shorts the wires and the ESC starts up.
groundFungus:
It will be easier to help you if you will read and follow the forum guidelines.
Hey GF I followed the rules now throw me a bone! 
Sorry, I don't know anything about that ESC. My post was an effort to get the information that others would need in order to help you.
groundFungus:
Sorry, I don't know anything about that ESC. My post was an effort to get the information that others would need in order to help you.
Fair fair. But with the knowledge that shorting the wires momentarily works to turn on/off the ESC, then what mechanism less bulky than a mechanical relay could I use? I've read about solid state relays, do you think this could work?
What isn't known is how much current the switch is switching. That would make selecting a transistor much easier. I think I did read the ESC (Electronic Speed Control) was rated for a 3 Amp maximum motor. I am also not quite sure what we are switching but a guess would be turning the ESC On/Off. Something you can try is measure from each wire to Ground. Next using a multi-meter set to measure current place the meter leads across the switch wires, we really need to know what the switch is switching.
Just My Take
Ron
I expect that the switch is simply switching a signal level current.
The thin wires are one indication.
An ESC is a motor controller and most motor controllers have an ENABLE input pin.
Most likely the remote just pulls that high or low. The only way to tell which would
be to check the voltage on both pins with respect to the battery ground (thick black wire on the Deans connector). If one pin is 5V then Enable is active High. If one pin is GND, then Enable is active LOW.
(the latter is probably more likely). I would also disconnect power and check continuity of both remote wires
to the ESC servo cable red and black wires to see if one of the remote wires goes to GND or 5V.
raschemmel:
If one pin is 5V then Enable is active High. If one pin is GND, then Enable is active LOW.
(the latter is probably more likely).
OK so with ESC powered, the red wire measures 13.7V (battery voltage) and orange wire measures 0V.
raschemmel:
I would also disconnect power and check continuity of both remote wires
to the ESC servo cable red and black wires to see if one of the remote wires goes to GND or 5V.
The ESC BEC connector (white/red/black) does not have any continuity with the remote wires (red/orange). Only the BEC black shows continuity to deans black (battery ground).
Ron_Blain:
Next using a multi-meter set to measure current place the meter leads across the switch wires, we really need to know what the switch is switching.
When shorting the remote wires with a multimeter, it measures 0.3mA which suggests a resistance of ~50kOhms.
Does all this point to a solution where I could use an NPN transistor?
One other tidbit of info, with ESC powered, I can trigger the remote by placing my multimeter in continuity mode between battery ground and remote signal orange. Is that because the multimeter is providing some kind of voltage to the orange wire when checking continuity against ground?
Actually that makes me wonder given that the orange wire can be triggered by multimeter, should I just run a wire between my Arduino digital output pin and the orange remote wire with a 10K resistor in between? Then I can send a high to trigger the remote? Maybe throw a diode in there for additional protection?
Try disconnect the battery and checking continuity from both of the remote wires to the male deans battery
connector terminals.
raschemmel:
Try disconnect the battery and checking continuity from both of the remote wires to the male deans battery
connector terminals.
There is continuity between red remote wire and deans positive.
Is the remote switch momentary or on/off ?
Check resistance (not continuity) from red wire to battery POS.
raschemmel:
Is the remote switch momentary or on/off ?Check resistance (not continuity) from red wire to battery POS.
Yes its momentary like an arduino reset button.
There is 0.4Ohm between switch red wire and battery pos.
A high side p-channel mosfet might work but
I would just go with a foolproof approach of a small 5V
relay to short the remote switch for 500mS
raschemmel:
A high side p-channel mosfet might work but
I would just go with a foolproof approach of a small 5V
relay to short the remote switch for 500mS
Yeah figured.... thanks for trying to find a solution.
