I’m trying to implement a remote kill switch for an autonomous robot. The robot is about 45 lbs and travels around 8 MPH so we would like to be able to shut it off without running to catch up with it.
Ideally we’d like a solution that is as simple as possible (the fewer failure points such as microcontroller code, the better).
I was looking at the WRL-07813 transmitter and receiver pair. In the description it says that “What the transmitter ‘sees’ on its data pin is what the receiver outputs on its data pin.”
Ideally I’d like a switch on a remote control to pull the transmitter data pin high, this would send the receiver data pin high which would keep a relay on the robot turned on.
My question is can I use the WRL-0781 as a switch like this, or can I only use it to send serial data?
The wrl devices you mention require that the signal be in bits. From the sounds of your description of what you want, you may want to look into automotive clicker type transmitters, wired properly they will only allow the robot to run while receiving the signal from the transmitter.
For what it is worth I made a remote e-stop for my college using the wrl series radios, and a pic 16f88 and some dev boards from spark fun. If you do enough testing and implement proper hardware usage and watch dog timers you can make a very reliable kill switch. Note that you should always have a manual kill switch easily accessible on the robot to shut down all power just in case.
I took your advice, jstiltner, and looked at the automotive switches. What I found was a wireless 1000m (range not tested by me) killswitch. The receiver/relay package and the remote (antenna and case) ran me about $40.
Would require a micro on the receiving end, but if your familiar with micro’s it wouldn’t be too bad. Then just hook it up to a big relay.
Best to keep the killswitch as isolated from the main system as possible, I would even run seperate power wires directly from the battery/power source.
Those are pretty nifty little devices, gussy. There are a couple reasons the prepackaged devices I mentioned win out over those though.
Price. After incorporating a microcontroller on the receiver, case and antenna on the transmitter, the key FOB and receiver are more than the ~$40 for the devices we used.
Range (the real issue). We wanted the longest range possible. The robot was a roving model where one person would be supervising it from a distance. 3280 feet works better for us than 100 feet.
For another robot, the two devices you mentioned could work very well. Two things I noticed: 3.3v for the receiver, and 5.0V for the transmitter. This would be ideal when the robot voltage isn’t at 12V (required for the kill switch we used). Also the kill switch we used took up quite a bit more space than these devices would have.
