Along the line of remote control rheostats, how about any info on remote control solenoid to activate a servo to activate/reactivate, push/ pull without the customary joy stick or turn knob from remote cars or airplanes? I guess it takes a special circuit board to translate the signal.

Thanks for any help in the right direction.

Dr. Solar

I'm not sure exactly what you are doing, but it sounds like you are adding an unnecessary piece of equipment to the "lineup". With an R/C servo setup, the servo acts as its own proportional "solenoid", which plugs into and is controlled by the receiver. If you are trying to control the speed of an electric motor, there are electronic speed controllers that plug directly into one of the receiver channels.

Check out any reference on radio control model airplanes or cars for all the information you need.

The benefit of the solenoid vs. the servo is that, it's easier to control. It's function is instantaneous... (think Jumbo Sidekick). For single function applications, they're great. They also don't need a servo driver or control, just apply voltage and they activate.

I've modified many 12 volt key chain remotes to activate solenoids and other apparatus by remote. Just press one button and the function happens... Works Great!!! Look up car remote kits and I'm sure you'll find what you need.

Mike

Keychain remotes work great. Surplus electronics shops often sell these along with the matching receivers.

If you're set on using hobby type RC systems, there are a number of ways to get simple on-off functions with these. One way is to use the control arm of a servo to actuate or strike a mechanical switch. Another way is to use an RC switch that plugs in place of a servo. These come in a variety of flavors depending on how big of a load you need to switch. Here are some that are popular with the robotic combat crowd:

http://www.robotmarketplace.com/products/rc_interfaces.html

I've made my own crude RC switches by stealing the amplifier from a trashed RC servo and using this to drive a relay.

Be careful how you go about triggering something that can bite. A single glitch can ruin your day!

Ross Hironaka

Thanks for the input. If I took a servo and applied a 9-12v current to it would that make the arms pivot? Would they just go one way and need to be reset manually? My initial question meant to ask how to get the servo to pivot one way and then resume the original position. The dealer at my local R/C hobby store said that servos for airplane models needed the joy stick or turn knob to activate it. But that seems only necessary if you want action in incrememtal degrees. No?

Dr. Solar

No, your servo won't work by just applying a current to it(*). Unfortunately, servos have a + and - connection (usually about 5v I think) and a control wire. The control wire is sent a series of pulses, and the length between pulses determines the position the servo arm moves to. A quick search of "RC servos" on the internet should give you the information that you need, but from experiance, I think that buying a ready-made servo controller board is the easier option than trying to build your own circuit!

(*) actually, when you apply current to the servo, without using the control wire, it will probably move to the "center" position, if it isn't there already. Perhaps a spring could be used to return the arm to another position when the power is turned off, but that isn't really the way servos are intended to work, a simple solenoid would do the same thing.

I experimented with a 12V car auto door lock solenoid. You can connect this to a RC device to trigger it. The only problem is that you have to reset it.

Are you looking for a way to just toggle between two discrete servo positions via R/C? Most R/C transmitters that have 5 or more channels come with a two-position "retract" switch. It's commonly used for retractable landing gear actuated by servos, where you only care about moving through the extreme positions (landing gear up and landing gear down). When you flip the Retract Switch in either direction, the servo moves to a (usually extreme) position and stops. Some fancier transmitters allow you to adjust the endpoints of the travel. To get the motion you indicated with such a setup, the operator would have to flip the switch one way, then back the other way, which could get tedious.

If you want a spring-loaded toggle switch, some transmitters come with a "Snap Roll" switch. This is a momentary toggle switch that allows you to trigger one or more servos to user-defined positions, then the servos return to neutral once you let go of the switch.

If your transmitter lacks the above features, it's possible to achieve the same functions if you're willing to hack your transmitter. Getting the right transmitter would be easier, though, if you can afford it.

If you're looking for the servo to automatically follow a pre-determined profile, moving from one position to another, then back again at a controllable speed, that's more complicated but still doable.

You can also drive the servo directly off of custom or ready-made servo electronics, as magicjohn suggests. This would bypass the R/C system and avoid any interference issues, provided you can live with the non-wireless setup. Any of the previously mentioned ways of triggering the servo would still be doable.

Ross