I installed the 315 Mhz wireless relay kit with my RPi last year. (robotshop.com/en/seeedstudio … witch.html) The transmitter is in an acrylic box, and the receiver is 25 yards away in a plastic tool box. Most of the time, the system works. However, depending on conditions, the transmission gets ‘chatty’ and the relay on the receiving side goes on and off making my pneumatic cylinder activate and return, activate and return. It’s usually so fast, that the cylinder only loses say an inch out of a foot long cylinder stroke, but it’s enough to make the end device unstable.
I’m assuming it’s underpowered. The solution is to touch a piece of metal to the antenna, and then things work out perfectly. I’m doing this by touching a nail to the inside of the antenna, but it keeps the lid of the acrylic box from closing. I don’t understand why this works, but it does. I want a more stable, solid connection. If I try to bend the nail at a 90 degree angle so the lid can close, the communication gets chatty again.
Basic operation:
Raspberry Pi -> GPIO, which activates a 3.3v relay, controlling 5v output.
Relay then goes to power the transmitter.
Receiving side:
Relay Receiver kit (12v) accepts signal and activates solenoid, then pneumatic cylinder.
The whole operation is “Held” there as long as the RPi is sending signal, usually about 15 seconds at a time. Then, I turn off the GPIO signal, and the signal is cut, allowing the cylinder to return.
The distance is set at 25 yards. No more, no less. Signal needs to go through 2 plastic boxes.
Is there a way to change the antenna from a coil to a means that would be more effective? Can I add an external antenna (or better yet, connect an external antenna to the coil antenna?). I tried different metals. A shorter nail does not work. The current nail prohibits the box from closing (not to mention not a long term solution).