WATCH BEFORE YOU BUY: PWM issue on certain ELRS receivers and some digital servos.

I stumbled on to a little problem with certain receivers running ELRS and Theta 989 digital servos. Watch this video to hear what happened and what do do about it. Thanks to PCBWay for sponsoring this video.

PRODUCT [AFFILIATE] and SPONSOR LINKS

REFERENCE LINK

RCVR CHANNEL LINKS

GENERAL AFFILIATE LINKS AND FAVORITE PRODUCTS

MY RADIO

[RCVideoReviews]

Point of Clarification: ESP32 is not exempt from the issue as is the case with BetaFPV SuperP using GPIO1 on PWM14. If an ESP32 does not use GPIO1 for a PWM output, it will not exhibit the issue as is the case with Radiomaster ER6 and ER8.

[MrZeek]

Great job John! I'm glad you guys caught this and hopefully there's a quick solution for it. And thank you for the dedication to this hobby and for other people. You're a good man! John

[crash_gordon]

Good info, thanks! Here's a list of the affected models from the json file:

BETAFPV PWM 2.4GHz RX (esp8285)
BETAFPV SuperP 14Ch 900MHz RX (esp32 + pin 1)
HappyModel EPW5 2.4GHz PWM RX (esp8285)
HappyModel EPW6 2.4GHz PWM RX (esp8285)
MATEK R24-P PWM 2.4GHz RX (esp8285)
RadioMaster ER4 2.4GHz PWM RX (esp8285)
RadioMaster ER5A/C 2.4GHz PWM RX (esp8285)

[darrenehlert]

Thanks John! Showing once again why your channel is the absolute best regarding edgetx and elrs. Great work and nice catch! Thanks for all you do for the hobby!

[geoffh]

John, this is a great piece of sleuth work by you and the ELRS devs! Imagine how much hair-pulling you have probably saved us by putting out this video!! If this alone isn't worth a Patreon subscription, I don't know what is! 👍👍

[johanopperman]

Thanks John just so glad you weren't in the air when this happened. Thank you so much for sorting this out for us. Very much appreciated

[simitarknut]

I am an Industrial Electronic and calibration technician, for 40 years, retiring the end of this month. This issue may be similar to some of the electronic noise issues I've encountered in recent years with modern motor controls, AC and DC. The newer digital servos may be throwing noise on the dc buss and the receivers may be getting 'confused'. It may be worth a try to install a small RF choke on all red servo wires, or if you can find a ferrite torroid(? spelling) (iron powder doughnut)that will allow you to pass the servo lead through and wrap around 2 to 3 times. If you have or can borrow an oscilloscope and monitor the voltage buss especially on power up you may see the noise.

[dingr]

Thanks for this. It explains the problem I discovered a few weeks ago on PWM2 output pin on two receivers (Matek R24-P6 and BayCK PWM RX) with a Savox SH0255MGP servo. Upon powering up, even before bind was achieved, the Savox servo on PWM2 was driven slowly to full lock and beyond the physical stop in an aileron linkage, damaging the linkage. I tried some other servo brands but they didn't have the same problem. I just moved the servo to another PWM output to work around the problem. Both receivers turned out to be ESP8285-based.

[BeaversHobby]

Thanks for the video. I'm looking into using ELRS with my cars and, well, they are all PWM. Worse still I use programmable servos. Safe to say I'm regretting my decision right now. This will probably result in using a receiver with more channels than needed and map the output somewhere else to avoid the issue.

[brunofporto]

It is a problem to be aware off. The incredible thing is that ELRS is so well done with the flexibility to remap pins that the workaround was already there :) really great to know, thank you very much!

[DGarrett-bt]

Started to have problems with my ELRS 915mhz DIY receivers a few months ago. Used the PWMP flash and only have three channels with chan one being the problem. Wouldn't connect when that servo was connected. Simply made a buffer with a 2n2222 transister and two resistors (1K and 10k) . Works great, never looked back!

[RubyS.]

Very interesting. Vbat telemetry alone is worth running elrs.

[alantoseland]

It is all very interesting, although I tend to use cheaper servos most of the time. Keep the good work you do up!

[steelrainfpv]

Whew 😮‍💨 I'm glad I bought the Radiomaster ER6's and dodged that bullet, thanks for the information on this potential problem.

[derrickmitchell]

Great Video! You really do a HUGE service to the ELRS community! Do you think you can do a new setup video for these new Radio Master receivers? I haven't seen any in depth videos on Youtube, only quick mentions that they exist.

[Katanacc]

Thanks so much for the vid.
Ya, i think those who work with esp32 for microcontroller projects are aware of "safe" and "unsafe" GPIO Pins to use.

[bitogre]

I would love to see more videos from you with Helicopters. Including using ELRS with telemetry on your helicopters. I am looking for RX to replace my FrSky RXs for both planes and Helis (I use iKon2 FC in my helis). For my helis, I am hoping to have the Main Battery Voltage and the Brain2.luac script for configuring the IKon2 from my radio work. Anything else would be a nice bonus.

[Coyotehello]

that video with its little quirkiness was the funniest this morning! LOL

[fd]

Great troubleshooting job John, thank you a lot! Fotios

[ulungprabowo]

I use ER4 for my tank and tracked robot. Its worked perfectly for a month and then this morning it is stop working.
I only use channel 3 & 4. I thought my ESC was burned but then I try the same receiver for my tank it is also not worked. Try to rebinding it and no luck.
I try my fpv drones and all working so definately my receiver.

Is it related to what you experienced?
It is the throttle that not worked.