AC and DC Servo projects with Kaflop+Kanalog

[Al_The_Man]

I have no info on the Renco encoders so I don’t know how I will ever be able to tell which wire does what.

The wire colours for Renco are pretty standard, I will dig a drawing up.

I’ve done another drawing here for a test setup using all the components for one axis. I used Al’s drawing (thanks) for the E-stop and limits. These are all NO switches so that when they register the 24V should “light up” the opto switches. Let me know if this looks okay.

Using the drawing I posted, all components outputs or contacts have to be N.C. the string basically retains the ESR relay when the E-stop Reset P.B. is released, otherwise it will be in permanent E-stop.
Al.

[Myk Bates]

I think I miss understood. I thought the opto switches were like a red light (stop) but it sounds like they are a green light (go). I see that in your drawing all the switches are closed on the 24v side and all go through the ESR. I'll have to do some more decifering on the com side. I dont understand Out 33, W/Dog, ESR, 2CR. What are they? They are open. Closing them would complete the link to Inp25? So tripping any of these would all register on the same input 25. I also dont fully understand the use of the ESR. How does it maintain the string?

Sorry for all my newness. Its just ignorace at this point. Hopefully all this will help someone else out as I try to figure out how much I dont know.

[Al_The_Man]

This should be it for the Renco.
Al.

[TomKerekes]

I’ve done another drawing here for a test setup using all the components for one axis. I used Al’s drawing (thanks) for the E-stop and limits. These are all NO switches so that when they register the 24V should “light up” the opto switches. Let me know if this looks okay.

The drawing looks better but still not right. You have a wire marked +24V going to the switches and then to the optos which is correct. But the wire marked +24V is coming from a Kanalog Connector which isn't correct. It should come from a +24V supply that you will need to add to your system. Also the Optos have a + and - connection. You will need to connect the - connection back to the - terminal of the +24V supply.

Think about a simple circuit with a battery, a switch, and a light bulb. It has form a complete loop for current to flow and light the light bulb. From the Power supply, through the switch, then through the opto, then back to the supply.

HTH
Regards

[Al_The_Man]

This also may help on I/O.
Al.

[Myk Bates]

Al, Great info. Thanks. I’ll spend the day absorbing it and figuring some things out.

Tom, I’ve corrected the drawing as you indicated. Thanks for the direction on what I am sure is vary basic stuff to you. I included a 24v supply and a 5v supply. I have the encoder powered from the Kflop. Should that be changed to the 5v supply? I also have all the limits and E-stop going to one terminal. That should be fine for testing but let me know if its not. I'm calling this drawing Revision D so I keep track of all my changes.

[TomKerekes]

Hi Myke,

You got it! The optos are now correct.

But the +5V supply has no ground connection to KFLOP.

Regards

[Myk Bates]

ooops, your right. I missed that one.

[Myk Bates]

Today was a lesson in what you don't know can cost you. Literally. I called US Digital today and ordered an PC4 and a cable. I was told the PC4 was necessary because the kanalog is using more than 5v. The PC4 does the same thing as the cable Tom mentioned but the cable can only be used for low voltage (5v or less) while the PC4 (plugs dirrectly into the encoder)can be used for up to (30?). Any way the PC4 was $40 the cable was $20 and the shipping was $12. Some seventy dollars later I almost could have bought a new encoder. I also could have returned this one but would have been charged a 35% restocking fee, plus the shipping Ouch. I just hope I got it right this time. Hopefully this will save someone else some money.

[Myk Bates]

I put a dial indicator on the servo shaft where the encoder will go. Turning it by hand it looks like the shaft is out by just under a thou. Does anyone know if that is enough to significantly affect the encoder? I’ve read that it can be affected but never was able to find how much was too much.

[Al_The_Man]

I called US Digital today and ordered an PC4 and a cable. I was told the PC4 was necessary because the kanalog is using more than 5v. The PC4 does the same thing as the cable Tom mentioned but the cable can only be used for low voltage (5v or less) while the PC4 (plugs dirrectly into the encoder)can be used for up to (30?). .

If you ordered US digital encoders, how come you did not order differential 5v output version?
Al.

[Myk Bates]

If you ordered US digital encoders, how come you did not order differential 5v output version?
Al.

The encoders are differential and 5v but are single ended signals. One A and one B channel. Kanalog uses +-7V differential input so I was told the EA 5v cable would not work and ordered the PC4 which does the same things but handles more voltage. This part gives me A+ and A- and does the same to the B channle. I didnt know about that when I ordered the original encoder.

[TomKerekes]

Hi Myke,

The encoders are differential and 5v but are single ended signals. One A and one B channel

You are mixing up your terminology. Single ended and differential are two different things. "Single Ended" means the just output A and B. "differential" means they output A+ A- B+ B-

Kanalog uses +-7V differential input so I was told the EA 5v cable would not work and ordered the PC4 which does the same things but handles more voltage

No that is wrong. Kanalog will work with 5V differential signals. 7V is the max allowed voltage where it will still work correctly. Actually only +/- 0.2V is required for the input to switch.

I put a dial indicator on the servo shaft where the encoder will go. Turning it by hand it looks like the shaft is out by just under a thou. Does anyone know if that is enough to significantly affect the encoder? I’ve read that it can be affected but never was able to find how much was too much.

I think such a thing will result in a small sinusoidal error in position. The amplitude of the error will depend on the radius of the encoder disk and your lead screw pitch. Imagine a perfectly centered disk with the read head at the top. Now shift the disk to the right by X inches. The read head will register that distance or X/(2 Pi R) of a rev. Multiply by your lead screw pitch to get the actual positioning error.

So for example X =0.001 R=0.5 inches Pitch=5mm

Amplitude = 0.001 /(2 x Pi x 0.5) x 5mm = 1.5um = 63 micro inches

HTH
Regards

[Myk Bates]

Tom thanks for correcting me. I feel like I am navigating through fog with only a bit of clarity here and there. One day I'll understand all this but the way my brain works it has to understand everything backward and forward before anything will make sense.

It sounds like differential must mean the difference between A+ and A-?

As far as the voltage does the encoder create the voltage and send it to kanalog through the A and B channel? And if so If my encoder is a 5V input will it only output up to 5V max?

[Al_The_Man]

A 5v RS420 or TTL encoder will output square waves from 0v to 5v, differential indicates that the A and B outputs have an exact complement, if you look again at the Renco PDF's I posted, it shows exactly what the signal waveform looks like for each output for a differential encoder.
Al.

[Myk Bates]

I cant seem to get ahead on this project lately. I have things shipped to my work address because I live in the sticks where mail is not always reliable. The encoder parts I ordered came after I left work on Friday and so I waited over the long weekend to get the box home. When I finally opened it I found that they sent me the wrong part. They sent me an EA cable instead of the PC4 that I had ordered. I'll have to wait to see what US Digital will do but it looks like I am derailed for another week.

[Myk Bates]

Looks like progress may begin again next week. I talked to US Digital today and they apologized for the mishap. I explained that the PC4 was ordered because I had ordered the wrong encoder in the first place. To make a long story short they agreed to take everything back and waive the restocking fee. They also offered to overnight me an E6 encoder that looks like what I should have ordered the first time. So come Tuesday I should have something to work with. I’m excited to get started again.

[Myk Bates]

I'm back working on this project for the weekend before leaving town for an entire week for work. Long days and hotel rooms.
So I have all the parts and pieces wired up. I checked the Axis screen to make sure the encoder counts are right. I basically followed the "Configuring DC Brush Motor with SnapAmp and Single-Ended Encoder to KMotion" Page on the Dynomotion website. The trouble for me is that uses a snap amp and I am using a AMC drive and a 32 amp motor. I have it set up in the TORQUE mode (I think that is what Al said he used). I backed off the current limit and loop gain settings until the motor stopped moving without commands, but I dont know what numbers to enter into the Step Response Screen. Tom had mentioned using DAC commands to turn the motor but I am lost on that too. I continue to scour cnc zone but cant seem to find where to start. Where should I start and how do I do it?

[TomKerekes]

The first step is to test all your wiring and such to show that KFLOP can command a DAC value that will create a DAC voltage that will go to the Amplifier which will create motor current and torque.

To test this command a small DAC value using the Console Screen and enter:

DAC0=100

This should generate about 5% of full motor torque. Even a small torque can accelerate to a high speed. So be prepared for this. Commanding a negative value should generate torque in the opposite direction.

You should not have the axis enabled for this test. If you do the Console DAC commands will not appear to work because the servo will immediately overwrite them.

HTH
Regards

[Myk Bates]

Thanks Tom. I disabled the axis in the step response screen and have the motor turning using DAC commands. The speed is fairly close in forward and reverse but it is not the same. I am using the TEST/OFFSET pot on the drive to get it closer. I have tried to get the motor to respond using the step response screen but have had no luck. Im not even sure what the values entered mean or what they should be but nothing I have tried has worked.