AMT103 encoder ground *WARNING*
 

The AMT103 encoder from CUI has a metal body. It is electrically connected to the ground pin on the connector. If the encoder is physically in contact with metal mounting hardware that connects to the robot frame, then there is continuity from the frame through the encoder to the negative terminal of the battery. If battery voltage is accidentally applied to the frame, something is probably going to burn.

In our case, that "something" was the ground wire in the ribbon cable between a Talon SRX and an encoder breakout board.

We have metal 10-32 bolts holding the am-0208 encoder mounts to the gearbox. We are currently in the process of replacing them with nylon bolts.

Re: AMT103 encoder ground *WARNING*
 

Wow, that's good to know. I hope nothing else on your robot was damaged.

Ugh...

Re: AMT103 encoder ground *WARNING*
 

Very interesting; we may have burned a wire up because of this. We were accusing a student of being overly aggressive on the heat shrink, but this is a viable alternate theory. Hmm.

Re: AMT103 encoder ground *WARNING*
 

I'm glad we build wood robots...

Re: AMT103 encoder ground *WARNING*
 

Thanks for the heads up.

Re: AMT103 encoder ground *WARNING*
 

Thanks ever so much for this information!!

I had the students go through the three AMT103 encoders on the robot and verify continuity to the frame and found one of the encoders was indeed shorting to the frame. It turned out to be the nut that is holding the mounting plate that we made was touching the encoder case. We just had to turn the nut to rectify it. We have added heat shrink to the nuts for now. We will be replacing the mounting hardware with Lexan instead of aluminum and as you suggested replace the steel bolts with nylon.

Again many thanks and good luck this year!!

Aloha

Re: AMT103 encoder ground *WARNING*
 

As a side note, our students have been destroying the clips and red sleeves on these encoders like they were popcorn. Be very careful manipulating the plastic tabs.

I've just discovered you can order replacements backs and sleeves for the encoders separately, which will hopefully help.

Re: AMT103 encoder ground *WARNING*
 

Dido

One inexpensive solution I found to this is get the next size up sleeve and add gaffers tape, electrical tape or some other tape to the shaft until it is snug.

Re: AMT103 encoder ground *WARNING*
 

Are these encoders electrically isolated from the shaft? I'm reasonably confident that we can keep the case isolated...but I'm sure the shaft is going to be grounded to the frame through a bearing or something.

Re: AMT103 encoder ground *WARNING*
 

A pair of plastic components isolates the shaft from the main body of the encoder, and I think the part they interface with is also plastic. I do not believe there is any risk of an accidental electrical connection that way.

We're using the "snow" (white) one for 1/4" (6.35 mm) shafts. Red sleeves are only 6 mm.

We determined almost immediately that the encoder bases are too fragile to reuse. Of the ten we started with, only two survived having the encoder removed without at least one of the three clips breaking. CUI pointed us to the "naked" encoder base in the Digi-Key catalog:

http://www.digikey.com/product-detai...322-ND/4835233

From that starting point, we found many individual parts that might come in handy. Digi-Key search URLs are not persistent, so I can't copy and paste here, but you should be able to navigate to Product Index > Sensors, Transducers > Accessories and choose CUI Inc from the Manufacturer list.