Any ideas on these encoders?

[RRRoamer]

Folks,

I picked up 6 Sanyo Denki P5 servos for a VERY reasonable price, three 100W and three 1kw servos. They appear to be almost brand new, which matches the description of their previous life from the seller to a tee. The smaller servos have grease in a gear reducer attached to the output shaft and the grease looks absolutely brand new.

The only odd feature of these servos is the encoder. All six servos have the same encoder on them: Kawasaki M21KA6Z0100B encoders. They are fairly small diameters encoders (case is about 1 1/2" in diameter).

The very odd part of them is the wiring. They only have four wires coming out:
Red
Black
White
Blue
and the wiring is done with what ALMOST looks like CAT5 twisted pair cable with red/black and white/blue twisted tightly and then the pairs loosely twisted together.

I pulled the case off of one encoder and it very much is an optical encoder with very tightly packed SMD components. In the quick inspection I was able to give the encoder, I did see a MAX417 (dual opamp) near the cable, but I did not have time to see how this thing is wired.

Anyone have any experience with these encoders? From looking at them, it almost looks like they are either outputting a differential resolver signal or possibly a serial type of communications. Needless to say, any help in figuring these things out would be greatly appreciated!

[samco]

my guess would be - they are just single ended quadature encoders.

power and A and B channels

black and red is power
white and blue are A and B.

(Just a guess)

sam

[Al_The_Man]

Also if not 0 to 5v on the A & B then check for a low signal sine wave output.
This type simulate a resolver in function.
With opamp fitted, this could be the case.
The other possibility to check if low signal is being single ended they may be open collector, if so they would need a pull-up resistor.
Al.

[vpcnc]

I think they are similar to this type of encoder.
http://www.usdigital.com/products/en...y/shaft/sp-16/

[Al_The_Man]

Those appear to be simple low res. encoders. 16 counts/rev?
If TTL out then you should not need a pullup and it will be 0-5v.
Al.

[RRRoamer]

They are definitely NOT low resolution encoders. There is definitely a high resolution glass encoder wheel in there and a LOT of SMD electronics packed on both sides of the board. None of that would be required for a low resolution encoder.

I should be able to do some more tests this afternoon and see what the scope shows me. That dual channel opamp makes me lean towards "resolver" more than quadrature encoder. Hopefully, it will be easy to find out!

One other thing: Is it safe to assume that 5V is the correct voltage (once I verify that power and ground leads to know chips...)? Are there very many odd ball parts that require lower voltage or higher voltage? The date stamp on the servos is 1996, so I can't see it requiring 3.3V or anything like that, especially given they are industrial servos.

[Al_The_Man]

I have never seen anything lower that 5vdc even for the Heidenhain sine wave out, which is either 1v p/p or 11µa.
Al.

[RRRoamer]

I dug a bit deeper into it. The servo has an integrated brake, so I had to apply 12V to that before I could even (easily) turn the shaft. The encoder itself is a three track unit with some very nice looking optical components above and below the disk.

There are also three major ICs on the bottom of the PCB:
1) 2S210-102 637100 that appears to be from Nikon. No datasheet found, but it appears to have something to do with decoding the encoder disk signals.
2) 2S237-024 as above
3) A TI 6LB176 ic that appears to be an RS-485 transceiver.

I did hook up 5V to the encoder and give the shaft a spin, but I wasn't able to get anything out of the white or blue leads. I really need to hook another motor up to this thing to keep it spinning at a decent speed so I spend more time scoping and less time spinning.

[RRRoamer]

Stranger and stranger. I did a bit more probing and found a couple of other interesting bits:
1) There is a voltage regulator on board. The MAX417 is getting 2.8V (within spec of 2.5V min) at it's input from an input of 4V to 6V at the red wire on the connector.

2) The outputs from the MAX417 do NOT go to the blue and white output wires at the connector. While reading the datasheet for the MAX417, it lists one of it's applications as a photodiode pre-amp...

3) I appear to be getting nothing on the output. I have pretty much ZERO experience with RS-485 drivers, so I have no idea what to expect. I was able to verify that the TI 6LB176 RS-485 driver IS the output driver. It's two output pins (6,7) check out as the white and blue wires in the connector.

Next steps to test this thing?

[Al_The_Man]

Strange, as RS485 is usually associated with differential output, and there is not enough outputs to implement the usual 2 outputs per pulse, i.e. each having the complement of the other, in an encoder without a 1 rev marker this would be at least 4 outputs.
But a single 6LB176 has only one output channel (and one IN).
So if the two encoder outputs were from a single 6LB176, you essentially would only have one signal and its complement??
Al.

[RRRoamer]

Originally Posted by Al_The_Man Strange, as RS485 is usually associated with differential output, and there is not enough outputs to implement the usual 2 outputs per pulse, i.e. each having the complement of the other, in an encoder without a 1 rev marker this would be at least 4 outputs. But a single 6LB176 has only one output channel (and one IN). So if the two encoder outputs were from a single 6LB176, you essentially would only have one signal and its complement?? Al.

A single RS485 stream can carry all the information needed to fully decode that wheel, even at 4500 rpm. It would definitely have to be sent as data instead of raw bit levels. So yes, it only has the + and - differential signals for a single RS485 stream. That also explains all the other high pin count ICs on the back of that PCB. There is a lot of processing going on inside there! I just hope someone comes along that has a bit more information on what was going on inside this encoder. Otherwise, figuring this out is NOT going to be quick or fun.

I suspect I will be looking into RS485 protocols in the near future..

[mike_Kilroy]

perhaps u would do better looking at sanyo danki for the answer? I googled and quickily found:

http://www.sanyodenki.eu/-200V-P5-SERVO-MOTOR-.html

the motor manual pdf download there describes a 'reduce wiring incremental encoder" which sounds like what u have. check it out.