Servo Switcher

[defy]

Hi Guys,

I'm wondering if anyone knows of a device which allows you to plug in two sets of servo inputs, to one set of servo outputs, and switch between the two. Basically so that manual control could be taken over a UAV while its in auto pilot mode, with a normal rc transmitter and receiver. I've done a bit of searching and can't seem to find such device.

[Tom Harper]

defy,

I'm using a CD4019BC from DigiKey. It's a quad 2 input AND/OR gate so it will switch 4 servos. For the switch signal I use the board from an old servo - replace the pot with 2 10K resistors. Since you only need 2 switches you can wire one of the outputs as an indicator.

[kd7ost]

Nice Idea Tom. Sounds very functional.

defy, here is a thread discussing such a project.

Dan

http://www.rcgroups.com/forums/showthread.php?t=360746

[Tom Harper]

Dan & defy,

The opto isolators look good but you still need a pulse width detector. The servo chip is an easy solution. This device will handle 4 channels. You could use one channel to drive an indicator.

[defy]

Awesome thanks for all the info :D

[LukeZ]

Tom, that's a very simple and elegant solution there. Thanks for sharing that.

Luke

[defy]

Hrm..digikey say its an "Obsolete item", would that mean its discontinued or out of stock?

[Tom Harper]

defy,

CD4019BE

Digikey 296-2038-5-ND

Tom

[defy]

excellent, thanks again.

[defy]

I used the 157 mux chip since it was the only one my local electronics store carried, with the servo guts idea as the switch and it works PERFECTLY. I have 4 switchable channels off of the one chip. I can go from auto pilot to manual control with the flick of a servo switch :D I was worried this was going to cost me a lot but it was completed for under $10, Thanks again!

[Tom Harper]

Enjoy!

[MattChave]

we use a cpld, that way we can detect when its out of range and do something. we'll be realeasing the code someday soon, we're just trying to make it fly properly first.

[defy]

I ran into that problem after thinking about it for a while as well. I solved it by connecting the switcher channels output to the ADC port on my robostix (I'm using a robostix and gumstix as my autopilot hardware). And then one of the pwm ports to the circut. Teaching the robostix how to detect a dead signal wasn't too hard, so now my auto pilot is in control of switching over to manual control. I dont know how well this will work in the real world. I know if i lose the use of the autopilot hardware in midair I wont be able to gain manual control. But for now it works.

[defy]

Hey MattChave, I see you're in new zealand as well, I'm in auckland. What types of projects are you working on?

[Unterhausen]

defy,
Is any of your code public? I have a stack of Gumstix/Robostix sitting in my office and I'd like to do something with them.
Eric

[defy]

A small portion of my code is public at the moment, and can be found at http://defy.net/balloon/

At the moment only my gps parser code is up there. Its just a small microperl script which parsers NMEA data a little better than gpsd does. gpsd had some issues returning the altitude on every request. (with the gpsstix anyway)

Next to go public will probably be my waypoint code, and then the auto pilot code, once its all finished.

[MattChave]

hi defy,
mostly this http://uav.bravehost.com

Good to see another person from nz in here. I had a look around your site, I'm also a paraglider and your parafoil rc plane looks very interesting. You should post some pictures on your site of it flying.