Instructables
One of the most common parts in remote control electronics is the servo. They offer proportional movement using a potentiometer, gears, a motor and an H Bridge Circuit. What we will be doing is taking apart a tiny servo to remove the circuit and potentiometer. We will then de-solder the motor and solder wires in it's place. These wires will then go to LEDs to light them up.

One interesting part about LEDs is that they are diodes (Light emitting diodes) so electricity will only flow through them one way. Based on this principle when we attach them to where the motor was, when the motor would be spinning one way, the electricity flows one way and will light up the LED. When you flip a switch on your transmitter it would make the motor spin the other way which makes electricity flow the other way but it can't becasue the LED won't allow it through the other direction. This essentially turns off the light. When paired up (the + of one LED to the - of the other and vice versa) when the motor spins one way, one LED lights up, flip the switch and that one turns off and the other turns on. This is what we will be making

Step 1: Take apart the servo

First you need to extract the necessary pieces. Remove the 2-4 screws to pull the bottom of the casing off, then pull the top off. Remove the gears as we will not need them. Then remove the potentiometer (It will have 3 pins and likely be what the main shaft of the servo rotates on. I had to cut my case to get it out without de-soldering the leads. You will then de-solder the motor and put it in your junk pile for some other project. 

Step 2: Prepare and solder your interface wires

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Circuit Drawing.jpg
I chose to put breadboarding leads on so I can experiment, however you can put on wires straight to the LEDs if you know your exact layout ahead of time. I cut the breadboard hookup wire in half so I was only killing 1 lead. Then I soldered each half on where the motor leads were. This will allow easy interfacing and prototyping. The Diagram below shows how the circuit works, note the position of the dial on the red servo tester. When centered (if the potentiometer is centered) neither light should come on. When turned one way, one color should turn on, when turned the other way the other color turns on. 

Step 3: Heat Shrink Time

You could easily use hot glue but it is harder to get back into the circuit if a wire comes out. I prefer heat shrink tubing. I put two layers around the circuit (so that when I put the potentiometer on it wouldn't poke through to the circuit). I then placed the potentiometer on top and slid a piece of heat shrink with a hole for the potentiometer shaft, shrinking each piece before putting on the next. 

Step 4: Done!

Now you have a remote controllable switch for lighting up LEDs, just plug it into your receiver. You will need to set up a switch and the process for doing this is different for every transmitter, follow your manual and figure it out. Also, you don't need to use a switch, you can use one of the sticks or you can do a mixing. One of the main reasons I thought up this design is so that I could mix it into the trainer switch. Then when I had control the craft would light up one color, then when I pressed the trainer button it will change the lights over and the trainee would know instantly when they had been given control. Give it a try and let me know what you think. 

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Showing it on auto (sweeping) with the servo to show what the commands going to the circuit look like.


This shows it plugged into a receiver and I am switching it on and off with the transmitter. 


 





 
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jaygreig8 months ago

Just curious how you ended up wiring your final project. How many total leds did you run? Wired in series or parallel? I am kicking around the idea of doing something similar on the 6v system on my 1/5 scale truck. I would like to run 12 5mm red leds in the rear and Y this into the throttle/brake servo to end up with functioning brake lights. I haven't actually purchased any leds yet, just tinkered around with some leds I have from previous projects, so I still need to figure up what specs I need on the leds. I would love to avoid having to run any resistors, which I am assuming with a 6v supply running 12 leds, I will have to wire in parallel and use at least one resistor. Will this end up draining my pack a lot sooner? (6v 4800mah)

I know I really need to start prototyping, but any advice you can give to start me in the right direction would be greatly appreciated.

Ben The Builder (author)  jaygreig8 months ago

In the demo I did 9 total, it's 5 in parallel one way and 4 in parallel the other way. You will have to use resistors, try an LED resistor calculator, they're all over the web. I might also suggest that you try using a small brushed ESC (3-10amps) but the downside is running it with a Y you will have trouble getting everything to line up. You could very likely run 12 standard 5mm LEDs off of the H-Bridge from one servo and then by turning the potentiometer you adjust the point where the lights come on. As far as draining your pack, you won't even be able to tell with one that big, 12LEDs only draw a couple hundred miliamps so if all you had connected was the LEDs it would take 24 hours of full on to drain your pack