Any electronics engineers in the house? Linear encoder repair questions. - Page 2

lendaddy · 04-12-2007, 10:21 AM

A few pics might help.

Porsche_monkey · 04-12-2007, 11:56 AM

And a picture of the other half...

lendaddy · 04-12-2007, 11:58 AM

Quote:

Originally posted by PBH
And a picture of the other half...

This is a similar setup wih both parts shown:

Porsche_monkey · 04-12-2007, 12:01 PM

And the track that provides the quadrature pulses is undamaged?

Can you replace the linear pulse train with one of dynapar's rotary units, driven from a drive shaft or motor on the machine? Or add ona small rack and mount a pinion gear on an encoder? that's how the old boring mill displays worked.

tobster1911 · 04-12-2007, 12:01 PM

Quote:

Originally posted by lendaddy
Interesting, would there be a way to test those four coils via the eight pins just to be certain?

Also, the speed does vary.

Would the surface of the coil getting exposed and possibly "shorted" via debris possibly cause damage to the board? Thanks!

You could test them by measuring the resistance of each coil from one end to the other. If three of them measure very similar and one is way off, you might have found something. The hard part is going to be finding out which two pins are the ends of the same coil.

A better measurement would be to measure the inductance of each coil, but this would require special equipment.

I looked up a similar system and they are using a 10kHz magnetic field. If yours is the same, those coils should have a capacitor on the PCB that is used to create resonance at the 10kHz. This allows them to be more "sensitive" to small signals at that frequency. If one of these was damaged, it could cause the signal to be missed. This only make sense if one of the coils is devoted or on used for the registration mark.

Could you take a shot of the PCB where the connectors attach straight on? Are there any components on the top side of that board?

lendaddy · 04-12-2007, 12:12 PM

Quote:

Originally posted by PBH
And the track that provides the quadrature pulses is undamaged?

Can you replace the linear pulse train with one of dynapar's rotary units, driven from a drive shaft or motor on the machine? Or add ona small rack and mount a pinion gear on an encoder? that's how the old boring mill displays worked.

The scale or "track" is fine we believe. We have two of them and they act the same. There are multiple problems with a rotory in the output and reference mark departments.

lendaddy · 04-12-2007, 12:14 PM

Quote:

Originally posted by tobster1911
You could test them by measuring the resistance of each coil from one end to the other. If three of them measure very similar and one is way off, you might have found something. The hard part is going to be finding out which two pins are the ends of the same coil.

A better measurement would be to measure the inductance of each coil, but this would require special equipment.

I looked up a similar system and they are using a 10kHz magnetic field. If yours is the same, those coils should have a capacitor on the PCB that is used to create resonance at the 10kHz. This allows them to be more "sensitive" to small signals at that frequency. If one of these was damaged, it could cause the signal to be missed. This only make sense if one of the coils is devoted or on used for the registration mark.

Could you take a shot of the PCB where the connectors attach straight on? Are there any components on the top side of that board?

Here are both sides of all three boards. They come apart on pins:

Porsche_monkey · 04-12-2007, 12:20 PM

Do you have a scope or digital probe?

lendaddy · 04-12-2007, 12:22 PM

Quote:

Originally posted by PBH
Do you have a scope or digital probe?

No, so I'm SOL best I can guess. Like I said earlier, this is a long shot.

lendaddy · 04-12-2007, 12:37 PM

I assumed by digital proobe you did not mean a multimeter, I do have a nice multimeter.

Porsche_monkey · 04-12-2007, 12:47 PM

This:

Not this:

tobster1911 · 04-12-2007, 12:48 PM

I suspect that these are the trim capacitors for the coils. This is to tune the resonant frequency like I mentioned. There are more on the other board. I am not sure how this play in.

I do not see any visible damage to the PCB or circuits showing. Without a schematic, I can only speculate on the circuits. Also without an oscilloscope to look at time-based signals this could be very difficult to figure out.

I think that maybe your best bet is to try to "hijack" the signal (that should be) sent to the motor when the registration mark is found. Do you know if one of these dedicated for that purpose?

lendaddy · 04-12-2007, 01:00 PM

Yes, the pink and grey leads are labled "ref" but I have no idea how to introduce the faked signal nor even what it would be.

tobster1911 · 04-12-2007, 01:41 PM

Quote:

Originally posted by lendaddy
Yes, the pink and grey leads are labled "ref" but I have no idea how to introduce the faked signal nor even what it would be.

The hard part is to find out what it should be. I would think these unico guys would be able to tell you this. I suspect it is just a high or low. You could do that with a switch. If it is a more complicated signal, it could still be done but you might have to use a micro-controller.

Let me know if you get any information from them. I am intrigued now.

lendaddy · 04-12-2007, 02:18 PM

Thanks, will do. We have been tracking down the last 11 of these sold back in '03-'04 and we are hoping to locate one tomorrow in overstock but they are closed for the day. I have to be honest in saying I hope I don't have to fix this one