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Sherman sudden acceleration when trolleyed around


Shad0z
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My Veteran Sherman has been working perfectly fine for over two years now, with no issues whatsoever.
But today I trolleyed it around, and it lost balance briefly, before accelerating to top speed, where I had to hold it down and try to shut it off, which I eventually managed to do.

I was worried the thing was gonna catch on fire, or that I had likely blown a mosfet, but after lugging it away and turning it on, the thing works perfectly fine, even tried riding it cautiously, and it functions completely normally now

However, I'm looking to have this NOT happen again, and make sure this thing is actually safe.
So I've opened it up, cables and mostly everything i could see on the control board seems fine, nothing is burned or seemingly off.

 

Any ideas as to what could have caused this, what to check, and any potential ways to solve this?

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Happens when trolleying in malls and public spaces. I think it may be RF interference. Likely the control board is not shielded against this radiation so it messes with the gyro.

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My Sherman has gotten weird around automatic doors a couple of times. It never took off, but started dipping forward and I had to rush to hit the power button to resolve the matter. Two different stores as well...

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  • 2 weeks later...
On 9/6/2022 at 2:22 AM, gon2fast said:

My Sherman has gotten weird around automatic doors a couple of times. It never took off, but started dipping forward and I had to rush to hit the power button to resolve the matter. Two different stores as well...

Seems like this happens at stores and malls specifically. I think I've nailed down the issue at play here.

Static from the floors. When you walk on them you generate static, that static goes through the trolley handle which you can sometimes feel walking in those stores, and where this is unique to the sherman is that the trolley goes right down next to the control board, it's covered by plastic, but I think what happens is the static interferes with the board in that way, and causes it to freak out for a moment, which results in a sudden dip or acceleration.

 

There are a few cases of this happening, and every case happened in a mall or store, which all have these smooth floors that generate a bunch of static when walked on.

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On 9/4/2022 at 4:11 PM, Mango said:

I think it may be RF interference

There has been evidence of the door post sensors [used to pick up RFID tags used to deter shop theft] causing issues with the hall sensors. So I agree this could be likely as you have stated.

https://www.sensormatic.com/loss-prevention/eas/detection-systems

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On 9/18/2022 at 2:13 PM, The Brahan Seer said:

There has been evidence of the door post sensors [used to pick up RFID tags used to deter shop theft] causing issues with the hall sensors. So I agree this could be likely as you have stated.

https://www.sensormatic.com/loss-prevention/eas/detection-systems

It sounds plausible, but as for the specific incidents including mine not actually being at or near said doors
and this being exclusive to the Sherman models, despite every EUC in existence having hall effect sensors.

My take is that it's due to the static generated by walking on the floors in malls / shops being transferred through the trolley handle, which on the sherman passes very close by the main board. Others had brought up static in relation to this issue before, and as random as it sounds, it's brought up for a reason.

When I trolley my sherman around certain shops I get very slight static zaps when I touch the trolley handle metal, I get this only in a few shops, and nowhere else, and I'm assuming static was brought up in the first place because others have had the same happen.

Edited by Shad0z
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On 9/4/2022 at 2:54 PM, Shad0z said:

any potential ways to solve this?

If its static, to confirm this I would try replicating the conditions again. You could create your own static electricity and use it to emulate the conditions and this should confirm your analysis and/or when next going to the shops wear and then don't wear antistatic gloves to see if you experience the problem again.

Or if you are 100% certain it is static (which it could be, I was merely answering the question of possible reasons) then can you use antistatic tape on the trolley handle? or ensure the area that the static can travel to the motherboard is eliminated. Could you use copper shielding around the ? I'm not an an electrical engineer so you will need to confirm this. Good luck. 

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