I modified a generic $1.60 LED controller to switch patterns from my TX

[Foamforce]

I used some cheap generic WS2815 12v individually addressable LED strips to build a night glider. It came with the little remote control that only worked within about 15 feet. It was fun trying to fly really close and changing the pattern as I flew by, but I wanted something better.

PS, before you suggest the MudLED, I know about that, and it's a much better solution than what I'm about to explain, but I enjoy tinkering, so that's my justification.

First, I got an ultra-cheap $1.60 LED controller on Aliexpress. It's labelled SP002E. By itself, it works pretty nicely and has attractive patterns. It doesn't have any remote control at all, instead it has three buttons for "next pattern", "speed", and "previous pattern".

I took the shrink wrap off that and first verified that the switches were simple momentary contact switches. When I bridged them with a jumper, they worked. I then measured the voltage at the high side of the switch, which was about 5v, and tried applying 5v to the lower side. That resulted in nothing but sparks. Surprisingly, no damage. I found a circuit diagram from Youtube which showed that the switches bridged between a pin on the micro processor and ground. So I guess these are pull-down switches, which I don't fully understand.

Next, I tried a transistor. I hooked up the collector pin to the high side of a switch, the emitter to the other side, and then added a resistor to the base, and connected 5v to that. That worked and switched the pattern as expected.

The last trick relies on a cool feature of ELRS PWM receivers. In the web interface for the receiver, there's an option to change the output of any of the channels from PWM to binary high/low. I set that and measured the output, which was <5v. Then I hooked that up to the base on the resistor and voila!

So now I have a single momentary contact switch on my transmitter that switches to the next pattern on the controller. Slick.

Was it worth it, vs a MudLED? Only if my time was worth nothing. Also, the MudLED has a big advantage in being able to control the patterns. I think what I would really like about the MudLED is being able to set the LEDs on the wing tips to red, green, and white, whereas my basic controller only allows colorful patterns. I'm also considering taking the Arduino approach. Is anybody aware of any other products that allow you to control LEDs from a PWM input?

 

[Piotrsko]

Could use the amp out of the servo that has stripped gears or crisped motor.

My pwm skills have gone south since everything is now addressed with packets

 

[Foamforce]

Could use the amp out of the servo that has stripped gears or crisped motor.

My pwm skills have gone south since everything is now addressed with packets

Do you mean to pull the circuit board out of a broken servo and use it as a PWM to binary high/low converter? Basically meaning that the DC output sent to the servo motor would be my signal? If so, it’s an interesting idea. I wouldn’t be able to directly use the 5v as my signal though, I need a relay. It’s possible that the servo control microprocessor is already driving a tiny resistor and I could use that.

Did you have something else in mind?

 

[Piotrsko]

Nope you understand perfectly what I intended. Servo control is done with a phase shift signal on old stuff, a digital word on the new stuff, isn't PWM per se, but timing between pulses. Either way the servo control decodes that signal and provides motor voltage. Also with diodes you could have two functions one forward biased, one reversed depending on stick position or switch use because your servo motor runs backwards returning to center. Not sure why you think you need a relay, mosfet perhaps for isolation, but you have a bunch of watts available to be dissipated by the removed motor. Logic levels on the light controller might be 3.3v instead of whatever the motor runs on (my stuff runs full battery voltage)
One caveat: unless the servo is crash damaged mechanically, the amplifier control is the typical point of failure

 

[Foamforce]

Nope you understand perfectly what I intended. Servo control is done with a phase shift signal on old stuff, a digital word on the new stuff, isn't PWM per se, but timing between pulses. Either way the servo control decodes that signal and provides motor voltage. Also with diodes you could have two functions one forward biased, one reversed depending on stick position or switch use because your servo motor runs backwards returning to center. Not sure why you think you need a relay, mosfet perhaps for isolation, but you have a bunch of watts available to be dissipated by the removed motor. Logic levels on the light controller might be 3.3v instead of whatever the motor runs on (my stuff runs full battery voltage)
One caveat: unless the servo is crash damaged mechanically, the amplifier control is the typical point of failure

Regarding the relay/transistor, I think I need that, and not just a 3.3/5v signal, because the switch in my LED controller can’t be activated by applying a control voltage to any pin. The switch in the controller shorts between a pin on the controllers microprocessor and ground. So my control voltage needs to control a transistor or relay to short that. Is there a different way to do that?

 

[LitterBug]

You could use an arduino instead of the controller. They are relatively cheap and you would have free reign to make it do whatever you want. There is however the programming learning curve.

 

[Foamforce]

You could use an arduino instead of the controller. They are relatively cheap and you would have free rein to make it do whatever you want. There is however the programming learning curve.

Yup, I’m considering that too. I’ve done some Arduino programming in the past, so it shouldn’t be too hard. Also, there’s a library called WLED for ESP32 that looks nice. It has an impressive looking web interface. Next project!

 

[LitterBug]

Yup, I’m considering that too. I’ve done some Arduino programming in the past, so it shouldn’t be too hard. Also, there’s a library called WLED for ESP32 that looks nice. It has an impressive looking web interface. Next project!

Yeah, there are quite a few "good" libraries out there. (fastled for example) I have some super high speed LED strips that I plan to use for a POV display with a TEENSY 4.0 or 4.1 board. I soldered extra RAM on the boards to store more images/animations.

 

[Piotrsko]

Even if you go the aurdino route you still need a mosfet or something to short the circuit. Are relays smaller than a TO-5 can? My self, I would remove that part of the circuit and try to run the led strip off the servo motor output.

 

[Foamforce]

Even if you go the aurdino route you still need a mosfet or something to short the circuit. Are relays smaller than a TO-5 can? My self, I would remove that part of the circuit and try to run the led strip off the servo motor output.

With the Arduino route, the LED control signal comes straight from the Arduino. The PWM signal from your receiver also goes straight to the Arduino. The LED controller isn’t used.

PS, I was using a little transistor for shorting the button and it works. No need for a mosfet because it’s only shorting a control signal.