Chris Anderson

Turning optocouplers into servo amplifiers

If you're using the UAV DevBoard with Futaba equipment or any other modern RC gear that outputs servo voltage of less than 3v, you're going to need a servo amplifier (also known as a booster or buffer) so the autopilot can reliably read your signals.
You can buy one from a commercial supplier like FMA for $15, or you can use our dual optocoupler and save yourself $10 for each pair of servos you amplify.

Out of the box, our optocouplers are designed just to clean up the RC signal, which is handy if you've got RF noise messing with your RC system. But if you solder two rails on the board (shown below), they become a very effective two-channel servo amplifier.


Make sure that the "input" side goes to the RC receiver and the "output" side goes to the servos or UAV DevBoard, like this (servo option shown):


When you're done, the servo amplifiers will take any input voltage and output a healthy 4.8v. Here's my scope data, from a Futaba FASST 2.4 Ghz system.

Before amplification:


After amplification:

Views: 190

Craig Palmer Comment by Craig Palmer on January 30, 2010 at 6:58am
how about a Futaba 6xa-fm ?
Chris Anderson Comment by Chris Anderson on January 30, 2010 at 9:53am
The older FM Futabas, such as the 6xa, output 3v, which is better than the 1.8 of the newer FASST ones. I'd still amplify for the UAV DevBoard

William Premerlani Comment by William Premerlani on January 30, 2010 at 1:08pm
Hi Chris,

Thank you very much for this posting this information. Its a great idea.

Best regards,
Bill
William Premerlani Comment by William Premerlani on January 30, 2010 at 1:18pm
Hi Chris,

One more thing, just to be clear: The booster connects between the Rx and the UAV DevBoard.

You do not need a booster between the UAV DevBoard and the servos, that interface is just fine. The DevBoard output voltage is nominally 5 volts.

Best regards,
Bill
Greg Comment by Greg on January 31, 2010 at 5:41pm
Great Idea.... After seeing this I realised I could use an opto coupler to convert 3.3V TTL serial to 5V TTL serial for a GPS output. This method could use 2 resistors and a 6 pin Optocouler.... I currently use 2 transistors and 4 resistors to do this. This idea could also be used for a TTL to RS232 line converter (once again 2 or 3 components ) - beats using a Max232 line converter and all the associated components.

Thanks for the Great Idea Chris!
Uzair Comment by Uzair on February 3, 2010 at 3:42pm
Handy tip.

Comment

You need to be a member of DIY Drones to add comments!

Join DIY Drones

Top Content 

1 ArduCopter 2.3 released

ArduCopter 2.3 released
2 Incredible Flight Endurance!

Incredible Flight Endurance!
3 Hunters shoot down Mikrokopter used by animal rights group to film pigeon shoot

Hunters shoot down Mikrokopter used by animal rights group to film pigeon shoot
4 MinimOSD meets ArduCAM OSD Config

MinimOSD meets ArduCAM OSD Config
5 jDrones ArduCopter Goes Color...

jDrones ArduCopter Goes Color...

Groups

© 2012   Created by Chris Anderson.

Badges  |  Report an Issue  |  Terms of Service

Sign in to chat!