TX/RX Labs Electronics Special Interest Group Message Board › R/C Servo for Chris's Camera Mount

R/C Servo for Chris's Camera Mount

Mark S.
user 97484812
Houston, TX
Post #: 3
Chris, after discussing the groups mission last week, I have decided that I gave you bad advice about your project. For the rest of you: Chris is working on an automated security camera. So he needs to make the camera pan and tilt. I suggested some starting points for building a servo motor system starting with a raw BLDC motor.

Having thought about it, I now want to suggest that you look at R/C servos. You probably have seen these, but they are primarily used to move the control surfaces on radio-controlled airplanes. Each servo includes a motor, a geartrain, a position feedback sensor of some kind, and the electronics to control these. You supply the servo with power and with a variable-width pulse. The pulse width commands the position of the output shaft.

Power in most units is 5 volts DC and they used to commonly run on 4.8V NiCd packs. I don't know what the state of the art is now that the batteries are mostly 3.6V but Mike Reynolds will know.

The pulse input is simply a 5V logic level. You can easily run it from a microcontroller pin (i.e. Arduino, Raspberry Pi, AtMEGA, PIC, etc) without any other signal conditioning. The relationship between pulse width and shaft angle varies between models and manufacturers, but is almost always centered at 1.5mS and generally about 1mS for CCW degrees and 2mS for 90 degrees CW. Unless I have CCW and CW reversed ...

Servos are available in a wide range of sizes and prices. Hobby King claims to have the world's smallest and it's around $5. At the other extreme, you can pay hundreds of dollars for large metal-geared units that provide high torques and run on higher voltages. For a camera mount, I'd look at Hitec. They have some reasonable Mama bear sizes and they have some waterproof units intended for model boats. This is likely another question for Mike, our resident expert on all things radio-controlled.

So, if you have an Arduino, a couple of these servos and some mechanical ability, you should be able to hack together a pan-tilt mount without designing H-bridges or worrying about gate drivers. Maybe you will bring it for show-and-tell to the August meetup!
Chris A.
user 25369232
Houston, TX
Post #: 1
Mark,

Thank you for your detailed advice. I will follow up on this and get the ball rolling. I will keep you posted.

Best regards

Chris
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