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Old Oct 10, 2015, 05:57 PM
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I'm confused about PPM vs PWM and my Dx6i

Hi there, noob here with a basic rx / tx question.

I followed a build guide for 180mm quadcopter and they connected only power, ground and channel 4 to a lemon rx. I want to do this, will my Dx6i work as a tx in this case? If so which lemon rx do I need? Seems there are ao many versions.

I ended up building it with an AR610 and it works but there are so many wires. Also I cant remember if PWM is the 3 wires or many wires but the build guide mentioned it.
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Old Oct 10, 2015, 06:04 PM
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This Lemon RX Spektrum compatible is for use with quad flight controllers that use PPM.
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Old Oct 10, 2015, 11:41 PM
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PWM is what a standard servo gets: a pulse is sent to it every 50 milliseconds, and the width of the pulse represents the position the servo is supposed to stop. PPM is a chain of pulses, and the position of each pulse in the chain represents the duration of the PWM for the channel that pulse represents. So, PWM represents a single channel, while PPM contains the info for as many channels as the transmitter sends. Both need only two wires: the signal, and a reference (like ground) to measure it. Servos require battery power, so a third wire is included to provide that. Receivers need power, too, and the third wire from your controller probably provides it.
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Old Oct 10, 2015, 11:55 PM
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For multi-rotor flight controllers, "PPM" means a single wire connection from the RX to the FC. As Wintr says, PPM is a pulse train that contains information on all the channels being transmitted by the TX. Unfortunately, most (all but one, as far as I know) Spektrum RXs do not support PPM, the AR610 definitely does not. To make this change, you would need to buy the Lemon RX as mentioned by 600Bob. Since you've got the copter assembled and flying, taking a little time to "clean up" the wiring, bundle things together with Zip ties, would probably be the better route. Save PPM for the next build you do. It's not going to fly any different.

I have a TBS Gemini Hex copter. I forget what the controller is. But it will interface with a Spektrum satellite RX, which outputs something like PPM. It makes for a very clean/small installation since the satellite is only an inch or so in size. So, even though Spektrum RXs don't have PPM (except for a brand new one they just released for Multirotor use) there are FCs that will work with a satellite RX which is essentially the same thing.
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