Servo failure

The USDA grant that funded the grower trials of the scarecrow ended in April 2024 and our ability to offer support will necessarily be reduced. Nevertheless, we are interested in your continued success in using these devices and would like to hear from you so we can try to help if we're able. For questions about how to use the scarecrow to protect your crop, contact Dr. Rebecca Brown: brownreb@uri.edu. For more technical questions (mechanical, electrical), please contact David Brown: david_h_brown@uri.edu. 

Servo failure/overload: We started seeing more servo failures than before in 2023 units and mostly solved the problem for 2024 by reducing the speed at which the servo moves. It's also possible to cause this sort of failure if the laser is forced too high or too low, jamming the servo. I've seen jammed servos that got so hot the plastic gears melted!

A failed servo can draw too much current and trip one of the self-resetting fuses on the circuit boards. This cuts power to the microcontroller, turning everything else off (including the servo), allowing the fuse to reset so the scarecrow tries to start again (and fails again).

This failure is easiest to observe in "ignore" mode -- jumper connecting the middle pins -- where the scarecrow stops after the pre-laser warning. The following video shows this. Notice how after the first pre-laser warning, the motor shudders to a stop and the power LED on the microcontroller flickers. The microcontroller did restart once, repeating the pre-laser warning, though the second time the LED did not flicker and it just stayed stuck. 

 Easier first check: 

The servo, laser, and tape sensor will all be disconnected if you carefully unplug the 8-wire "Slip Ring" connector located on the side of the board away from the key switch. There is a ridge going all around the plug that you will need to pull straight up -- one end then the other rocking back and forth is okay; just don't pull on the teeny wires. 

With the cap on the laser(s), start up the scarecrow. If the problem has gone away, it's one of these, but not necessarily the servo. (If the problem doesn't go away, it's probably not one of these.)

 To verify the servo is the problem, disconnect the servo connector only (inside the rotating arm in 2022 and 2023 models; see assembly guide; for 2024 models and 2025 Berry Prototype, see below). If the scarecrow can then operate normally (except of course that the laser won't tilt up and down), the servo will need to be replaced; see the page where we list replaceable parts. 

2023 servo connections

You connected the servo in section 2.10.5 of the 2023 Kit Assembly Instructions (find links to the manuals here). Look for a 3-wire cable (white, red, black) going into the end of the rotating arm. Remove the PVC endcap if present, and gently pull out the cables (it's fine if the cable manager comes off, too). Be sure to remove the servo cable clip first and pull the plug and socket, not the wires themselves. 

2024 and 2025 Berry Prototype servo connections

The servo connector is a black rectangular plug with three wires near a white rectangular plug with two wires (for the laser). To disconnect a servo, just pull the plug straight back out the side of the cap that is over the small circuit board that's on top of the rotating arm. They are held by the friction of the pins (and the cap). 

To reconnect, make sure you align the darkest wire to the outside (black or brown); lightest wire to the inside (white or yellow) as you push the tip of the plug back through the opening in the cap. The three shiny points you can see about ½" (13mm) in from the edge of the board are for the right-angle pins you are trying to push the plug back onto. It can be tricky; try tilting the tip of the plug up so it slides along the bottom of the circuit board until it is stopped by the pins hitting the plug housing. Then back off just the tiniest bit, level the plug, and push it onto the pins.

These photos show the scarecrow upside-down as it’s easier to work on the scarecrow that way: