Now that there have been a couple events under the belt for this machine: sons birthday party and a carnival, I am looking to make the claw machine more noise immune.  

The last event showed a random reset of the machine that would cause it to home out. As if the program was being told to reset or an MCLR pin had been set low.  Not sure where else to look, I intend on doing the following:

1. Replace all wires running to limits and joystick with shielded cable wires.

The joystick is no longer screwed to the frame.  I can move it freely like a wired remote.  It has also been updated to use a shielded cable.  I then checked to see if a plasma cutter will cause resets when it first fires an ark.  It still did.  I then proceeded to remove the z axis (claw height control) and also the limit switch for the z axis.  These both were no longer being used as I removed the claw and claw drop motor for testing with a plasma cutter.  Once these were removed my reset problem quit when firing the cutter.  But if I would touch the plate being cut to the grounded frame (using a groudn lead from my controller box and being grounded via the outlet), then the machine would reset.  This lead to looking into grounding practices on CNC plasma cutter machines.   It looks like these installs include a grounding rod at the machine and grounding the machine to it.  I will attempt this in the near future as there are steel tie downs in the concrete in the shop I am using.

Tried a second night of squashing noise from causing problems.  Grounding to the tie downs did not seem to cure any problems.  What we did notice was that when the plasma cutter was sitting on a trailer, we could not get rid of the reset issue, even if we kept the ground for the cutter away from the grounded frame.  Once we placed the plasma cutter on the ground then it would work fine until I touched the work to the frame.  

We also tried to throw the whole controller into a stainless steel refrigerator with all sides grounded.  This still did not cure the problem.  What did finally cure the problem was when all wiring was pulled from the frame and placed inside of the refrigerator.  When I would connect the limits back up then the problem would reappear.  If I would unhook the limits and hook the motors up, the problem will still exist.  The motor frames are grounded to the frame but the cable shielding is not grounded to the frame, only at the controller.  There is about 4 inches of unshielded cable right near the motors. There is also about 12 inches of unshielded cables running to the limits.  The limits are also NO.  This might be changed to NC to hopefully get rid of some of the noise.

2. Make a PCB for the PIC or ditch and convert to an UNO I purchased a little while ago.

The board has been designed.  I am planning on milling out the pcb with a CNC mill that was purchased.  This is a slow process as it is 3 phase and as time allows I have been getting a phase converter up and running that is contained.  Also had to build some fixturing to raise the bed up to allow for direct bolting fixture plates.  The board uses opto isolators to isolate the outside switches from the controller.

3. Find complete metal enclosure and place electronics inside.

Will still maintain the computer box as that is what I have for now.

4. Look into noise immunity between the A4988 and the controller.  Look into RepRap boards to see how those are designed.

The new board designs will utilize opto isolation between them.  Will also use two different 5V power sources. 

5. Look into more filtering on the 110V side.

Found a filter from a copy machine and plan on installing this also.

This is as far as I can see into mitigating this problem as I do not have much experience with this.  We will see where this leads. . .