Re: A very weird digital sidecar problem...
 

Patrick,
I will bet dollars to doughnuts that your have some wayward metallic debris in the DSC. I helped a team with a similar situation locate one single metal flake that had fallen down between pins on the DSC. You need a very bright light. You might have to remove the DSC from the robot, remove the cover and check inside but I am betting that is what you will find. It is likely it is right next to the pins for your encoders.

Re: A very weird digital sidecar problem...
 

Even the brand new, still-in-the-antistatic-bag one we replaced the first one with? Metal shavings was one of our first investigatory culprits; we found none.

Re: A very weird digital sidecar problem...
 

Patrick,
Did you tell us the model number of the encoders you are using? I did a quick check but didn't see a number in your earlier posts.

Re: A very weird digital sidecar problem...
 

We had a very similar problem in Portland. We burned through three DCS's, and no one could figure out the problem. All of a sudden in a match, our robot would quit driving. We checked all of our connections, changed the PDB, swapped DCS's, and checked for metal shavings, yet nothing helped. The only thing that fixed the problem temporarily was a new DCS.

Re: A very weird digital sidecar problem...
 

Sorry, I was out sick yesterday -- feel much better after having spent 20 of the past 24 hours asleep!

We are using these: http://www.andymark.com/product-p/am-0791.htm

Re: A very weird digital sidecar problem...
 

Pat,
These encoders are virtually indestructible but there are a few peculiarities. The first is the encoder base is molded so that the encoder PCB only fits in one way. The other way causes the PCB to be bent due to the through hole electronics not fitting into the recess in the base. When you mount it, and hog down on the screws, it is possible to bend over the through hole leads or damage the PCB itself. Since the PCB does not have conformal coating it is of course easy to get shavings inside. The LEDs internal to the encoder are visible and can easily be seen when the encoder is correctly powered and the cover is off. It is also easy to bend over one or more of the pins in the white connector.

Cierra,
Is it possible you wired the DSC to the 24 volt power on the PD and not from a simple 12 volt output on the PD?

Re: A very weird digital sidecar problem...
 

I'm 99% certain none of that is the case here, but will double-check all of the above when we unbag at Buckeye. Thanks!

Re: A very weird digital sidecar problem...
 

Pat,
I should have also mentioned that while extremely hard to do, it is possible to plug the white connector in backwards. I think you only hope is to recheck everything at this point, including the encoder wheel position relative to the board.

Re: A very weird digital sidecar problem...
 

:eek: I think that would take some serious effort! (I'm certain we didn't.)

That's what I'm thinking, too. Thanks for your help.

Re: A very weird digital sidecar problem...
 

Al -

Is it possible that the mis-assembly you described to short out the DSC's power?


Cierra -

What do you mean by "burned through"? Are you sure you were destroying DSCs?

Re: A very weird digital sidecar problem...
 

Eric,
I am grasping at straws here to understand what might be happening. Pat seems to have checked most of the obvious stuff so now it is time to move onto the other not so obvious. I know one of my students assembled this encoder backwards on the base a few weeks ago. The board cracked in the exercise due to the mounting screws but it is also possible to bend over the tabs on the connector and cause a short between the 5 volts and the adjacent pin. I know another student from last year had managed to push in the connector backwards but the result was almost ripping the connector off the board. I don't have one here at work but as I remember there is only one LED assembly with two photo transistors or diodes and a couple of resistors. There is even the possibility that the mounting screws had been substituted for larger screws which could play havoc as well. I can't wait to hear what Pat finds out.

Re: A very weird digital sidecar problem...
 

Assuming we manage to track it down next Thursday, you can be assured I'll be posting the results here (though likely not until after Buckeye is over.)

Re: A very weird digital sidecar problem...
 

Update: We could not recreate the problem.

The good news is that this means we were shooting in autonomous and even scoring some balls at Buckeye. The bad news is that we have no idea what happened or why.

I've spent the past few days going over the robot with a fine-toothed comb (and oscilloscope) after school, and I can't find a single, solitary issue with the electronics, wiring, or sensors.

Thanks, everyone, for your input into this problem... I wish I had a more satisfactory conclusion in terms of problem identification and resolution, but I don't.