Don’t worry about not having reverse servos anymore because these days you can buy compact servo signal reverser modules at very low prices. A servo signal reverser, as the name implies, can rotate a forward servo in the reverse direction and a reverse servo in the forward direction. All you have to do is connect the module in series with the servo channel that needs to be reversed. That’s it!
Out of curiosity, I recently bought a few cheap servo signal reverser modules. In this post, I’m going to give you an introduction about a generic low voltage servo signal reverser module randomly picked from that assortment.
This is my generic low voltage servo signal reverser module. As you can see it’s a tiny stamp sized module with two servo lead extension cables.
As you might guessed, one connector (female) is for servo input and the other one (male) is for servo output.
The module’s single-sided PCB is populated only with chip components (SMDs) and the entire electronics is covered with a transparent heat shrink tube. Since one side of the module is blank, we can use that surface to stick the module anywhere in the specified area with a drop of glue.
After removing the transparent sheath, I scrutinized the circuit board and found that it carries only a few parts. As you can see, part number of the core component (perhaps a microcontroller) has been rubbed out by someone.
These are the key parts I found:
- 8-Pin IC x1 (Unknown Part – May be a PIC uC)
- 2SC1623-L6 Transistor x1 (SMD Code L6)
- 10KΩ Resistor x2 (SMD Code 01C)
- Nonpolar Capacitor x1 (Unknown Value – Probably 100nF)
(2SC1623-L6 Datasheet https://datasheetspdf.com/pdf-file/594110/MCC/2SC1623-L6/1)
You can see the schematic I’ve prepared after using a multimeter for a few minutes.
The intention of a servo signal reverser is to invert the servo command signal by mirroring the pulse around 1.5ms which is the center on a servo. That means, for a 2ms pulse input, the reverser will output 1ms and for a 1ms pulse input it will output a 2ms pulse.
This can be realized with a couple of transistors, or a Quad NOR gate IC can be exploited to do that. But a tiny microcontroller will probably take up less space on the circuit board and needs less components than the discrete version. Here you can find an interesting servo signal reverser project idea centered on a PIC12F675 microcontroller http://bhabbott.net.nz/Reverser.html
I’ve implemented a basic functionality test using a cheap servo consistency tester – really nothing special but some sensible outcomes. It should be very easy to employ an Arduino or Raspberry Pi to test this module (I have not done that yet).
I used an oscilloscope to see the pulse trains rendered by my servo signal reverser module which’s relative to the servo pulses generated by the servo tester. An oscilloscope is a good thing here because it can help you understand how the whole thing works. You can take a look at the random oscillogram down below.
To sum it up all, I’m happy that I was able to get and test a cheap low voltage servo signal reverser module. It doesn’t have too many functionalities but at least it works. Maybe I’ve inspired you to make your own low voltage/high voltage servo signal reversers – it’s really not as hard as it looks.
And that’s all. I will update this post if I find out something more. As always, you can post comments down below(If you have any questions feel free to ask).