Building a manually-controlled touch screen tapper for controlling farm tractor GPS

Thread Starter


Joined Apr 1, 2022
Hello, first post here. I apologize for what will be a long post. I'm basically trying to create one of these, but one that I can manually control instead of having it tap non-stop:

Aside from engineering, I also farm. Our tractors can be driven via GPS though our Agleader Incommand 1200 displays: They do this by following a set guidance line and then automatically follow that line through the field. There are some touch-screen buttons on the display that allow the driver to manually nudge the tractor left or right from that guidance line if needed. See pic.


My problem is that the most convenient place to mount the display in the tractor is frequently not very convenient to be reaching over and manually touching the buttons on the screen. Therefore, I want to make a simple wired remote control that will simulate touch the screen whenever I push a physical button.

From what I've read, these displays are capacitive touch screens. I experimented today with taping a piece of aluminum foil to the screen and then running wire leads from the foil to a switch, and then from the switch to a spool of heavier gauge wire. (no electricity actively involved in the circuit) I discovered that so long as the initial lead from the foil to the switch was short and used a light-gauge wire, then the screen did not sense the foil and the initial lead. However, once I closed the switch, it would sense touch due to the longer, heavier gauge wire on the backside of the switch.

This was great, except that the initial lead had to be so short such that I really wasn't gaining anything to use the switch instead of the actual touch screen button. So, I experimented with placing a relay that we had laying around into the circuit. This relay is a fairly heavy-duty 12vdc that I've seen called a starting relay. Theoretically, using the relay would allow me to place my switch farther away from the screen while still keeping the initial wire lead from the foil to the relay short.

When I did this, the screen did not sense the foil when I had it hooked up to the relay with the switch off. I also tested and there was no continuity between the relay terminals that I was using to connect the initial lead to the heavy wire spool. Perfect. However, when I close the switch, the relay clicked, but the screen did not sense the foil. I probed the two relay terminals, and there was now continuity between them. I also tried ground the wire spool to the tractor and also to the monitor itself via a usb cable that I stripped down and plugged into a USB port on the side of the monitor. I connected the wire spool to the ground lead in the usb cable. Neither of these things helped. For some reason, adding the relay into the circuit is preventing the screen from sensing the foil, and I cannot figure out why.

I'm a mechanical engineer. I typically leave stuff like this to you sparkies because I usually end up letting the smoke out of everything. I got a nice whiff of burning wires today from a cab fan I supposedly fixed. So, if anyone has any suggestions on how to improve my circuit, or even how to possibly hijack the tapping probes used in the product in the amazon link above, I'd be very interested in hearing your ideas. Here is another product where in the photos of the product you can see the chip they are using: If anyone knows what the chip is and sourcing and using a similar chip isn't difficult, I'd be willing to look into that as well. thanks in advance.