Encoder Trouble HELP!!

[ty1295]

System: Rutex drives, Micro 100 Servo with a HEDS-5605 A06 encoders.

System was running great last week, shut down power, etc.

Go to use it, one axis goes wild, other doesn't until you go to move then continues to spin.

Track it down to encoders. Both are bad now. If I hook up my 3rd motor/encoder (which I had not installed yet) things work.

How did I manage to blow up encoders? Was it a fluke? Did I overcurrent them (BOTH?). I did operate machine successful for about 3 hrs, would think it would have blown during use, not while powered down.

Did a storm somehow affect them, but nothing else electrical, even though it was all off?

I have a resistor from the +5v to each channel A and B per rutex instructions.

Help, need to get it fixed ASAP but don't want to mess it up again.

Jeff

[snaggletto]

How are you powering your encoders, and what is the current rating of the supply?

[ty1295]

powering them via the rutex drive.

Did I somehow overpower them? Should I add a current limiting resistor, and what size?

[ynneb]

Just out of interest, is there any chance the encoders were swapped over where they pulg into the Rutex cards? If so, this will cause your srevos to run away. Please report back if this was the solution.

The symptoms you suggest are exactly the same as swapped over encoders. I know this problem first hand.

[ty1295]

That is the odd thing.

I ran machine for ~4hrs when I first got it going, due to other projects, time, etc didn't get a chance to play with it.

Electroics were turned off, cabling left intact.

Went back ~4days later, turned main power on and motor takes off on 1 of the axis. The other one continues to run if you give it any movement commands.

So last night I plugged in the encoder from my 3rd motor which was not hooked up last night, with power wires still going to mounted motor. As I would expect, as you turn shaft on encoder motor other spins, turn other way it stops then spins backwards.

Plug it back into correct encoder on motor, motor spins non stop on 1 axis.

HAd it been cabling I would have known, as I was "smart" enough during initial setup to have tried every WRONG combination.

Going to order some new encoders today from USdigital, with some of their made up cabling for it. Just don't want it to happen again.

[snaggletto]

Hey,
You need to know how much current your encoders are pulling and how much current the Rutex encoder+ 5V terminal can supply. I've got two different types of encoders and they both pull more than the 50ma that my Gecko encoder+ 5V can supply. I had to use an external +5V power source that had enough current capability on my setup.

I don't know much about the Rutex, you need to verify, but I'm guessing it will work like my Geckos. When powering the encoders from an external supply;

1) hook the +5V encoder wire to the +5V on the ext. power source
2) hook BOTH the encoder ground AND the power source ground to the Rutex encoder- (or ground) terminal.
3) jumper a 220Ohm resistor from encoder+ to encoder- on the Rutex terminals. This simulates a load to the Rutex +5V power source.

Please verify how this is done on your Rutex drives, this procedure might only work with the Geckos.

[ty1295]

I can see the encoder NOT working due to not enough amperage.

But they worked, and the 3rd one I hadn't installed yet still worked. So rutex had to be suppling enough, unless they required more current after a few hours use.

I may try to power them up tonight externally and see if the come to life.

[ynneb]

Actually,Snag may have a point.
I seem to remember other in this forum having issues with the Rutex power supply not been up to the job.

Also, if the encoders are not differential, you can only run limited distance of control wire to them. Did you put the resistor in the line as described in the Rutex instructions?

All these things may be causeing intermittancy.

[arvidb]

If all encoders worked just fine until you switched power off, and then two of them didn't work next time you switched power on, that sounds to me like you had some kind of spikes either at turn on or turn off.

Were any of the motors running at the moment you turned power off? Where in the system is your power switch located?

Arvid

[ty1295]

Power switch is located on the 220v input into my control box.

Is a main disconnect that turns everything on/off except for the PC.

The problem was discovered when I power up machine, table instantly headed for the nearest exit it could find. When you not expecting it, can make for interesting time.

Encoders were wired per Rutex instructions.

If it isn't a lack of voltage to encoders I can only assume a spike or bad luck.

I do have new encoders with wiring on the way from US Digital, hopefully arrive today.

Just hope it doesn't happen again. Will try to power one of the old encoders with external supply and see if that works. Still doesn't make sense why I can plug in the unused encoder and it worked with same wiring.

[snaggletto]

Hey,
It's not the voltage, 5V is 5V. It the amout of current that the Rutex can supply (50ma, for example) vs. the amount of current the encoders pull (150ma, for example). If you overload your Rutex 5V supply, you will burn it out. If your encoders don't get the juice they need, they may not work correctly/reliably. Hook your multimeter up in-line with an encoder to an external 5V power source (computer PS) to see how much current the encoder wants.

There are 2 possibilities;

No power (or not enough) to the encoder. Confirm 5V at the power source and the integrity of your wire and connections

No signal (or bad, noisy signal) from the encoder. With no power to the servo, but power to the encoder, you should be able to see (multimeter) the encoder A/B signals increase or decrease in voltage as you slowly turn the motor shaft by hand, up until the Rutex faults out. Then the voltage should reset to 5V.

The encoder signal wires are very sensitive to EMI from other wires/devices. You should have shielded wire for your encoders. The encoder wires should not be routed near power wires, and should be as short as possible.

Ironically, I highly recommend that you read the Gecko G320 users manual on geckodrive.com. Yes, I know you have Rutex, however they both work in a very similar manner. The Gecko documentation has some testing procedures that should work just the same on your Rutex.

Keep us updated.

[ty1295]

Made some progress tonight but not sure why yet.

Got new encoders today from US digital, while I was ordering I also ordered up cables at the same time 12 ft long. (just barely long enough for what i need).

Installed new encoder on 1 motor, had to reverse power leads on motor to prevent overrun.

During tuning motor was VERY slow to stop and graph jagged.

5v from rutex to encoder didn't waiver at all, was a strong 5.2-5.3 volts at all times.

For kicks installed external power supply. Same problem.

Finally added some pull up resistors (figured with new cable and short, shouldn't need it, was I wrong) and things are working good on the 1 motor.

Too late to adapt other motors to new encoder setup.

Of course above took 3-4hrs, as I left out 95% of the things I tryed.

I am fairly confident old encoders are not working properly as the external -vs- rutex 5v supply didn't change anything.

Pull up resistors were a MUST.

Even with new cabling I got some obvious noise while moving wires around. I knew wires were sensitive, but not THAT sensitive.

So progress made again, but like the whole project has been, to make 1 step forward requires 21 steps, 10 backwards, then 11 back forward.