Victor 888 PWM Problems

Technical Electrical
#1

Hello everyone!

I am here on behalf of FRC Team 5196, Breaking Bot, and we’re experiencing some problems. After the second our kits arrived where we were hosting kickoff, we began to build the kit bot and finished it with in a few hours, as well as all of the programming aspects such as flashing the cRIO and the wireless bridge. When we finally set the robot on the ground to test it with a joystick, the Victor 888 motor controllers would not stop flashing amber/orange, which (according to the manual) indicates that they are receiving no PWM signal.

We disconnected one of them from the motor and hooked it’s power and PWM cables to our only Jaguar motor controller and it worked completely fine. We then took the Victor 888 inside and tested it’s PWM with an Arduino and oscilloscope and it was still creating the same problems.

Is anyone else experiencing these problems with the new Victor motor controllers, or does anyone know how we can troubleshoot the problem?

Thanks!
FRC Team 5196, Breaking Bot

#2

Hey again!

After further investigation, we disassembled the Victor 888 and connected the Arduino directly into the sockets for the PWM connectors and it worked and turned a motor.

We confirmed this by reassembling the Victor and placing the PWM male cable as far into the socket as possible and tested the controller. This resulted in the flashing orange light. We then removed the shell of the Victor and placed the PWM male cable as far into the socket as possible again and tested the controller. This resulted in the controller detecting the PWM connection and spinning the motor.

With the shell removed from the controller, we tested the female socket to see where the PWM signal was not detected. The PWM signal was detected all throughout the female socket aside from being removed.

From our testing there is an issue with the shell interfering with the PWM connection with the motor controller.

Sorry for the double post, and hopefully other teams with the same problems see this!

#3

Hey! A Dog IRL!

In your code, whether it be Labview, C++ or Java, have you set your motor controller type to the Victor type? FRC code is defaulted to Jaguar, and that doesn’t work with Victor, so you’d have to change it, recompile, and load it back onto the bot.

#4

Getting your PWM cables seating into a Victor with the shell on it is challenging. This is a good thing, it means that the cable is less likely to fall out at an inopportune time. You are most likely not getting the cable fully seated into the port.

#5

Yeah, we actually fixed it by using 22 gauge wire and plugging that directly into the connectors as a temporary solution until we develop a better one. We have that connected to the PWM cable.

#6

Make sure all your pins are straight before inserting the connector. You will need to put a fair amount force into the connector. It needs to go down quite a ways. Take it out and try again if you don’t get it the first time.

#7

Be careful with the “fair amount of force” thing. If it takes too much force, you’re probably bending the pins.

Does anyone reading this have an 888 with the PWM connector fully seated? And if so, would you please measure and post how far the fully seated connector extends out from the body of the 888? If your installed connector substantially exceeds this measurement it is probably not fully seated.

#8

That’s why I said make sure the pins are straight, but yeah, don’t apply too much force, and don’t use an arbor press or a hammer or anything like that.

#9

OK. Attached. About 0.26 inch, fully seated.

PWM888.jpg
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PWM888.jpg
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#10

Victors have always been notorious for this problem. It takes a real knack to get them in right, especially when they’re buried behind or under some other component, as they always are.

The Talons, which have the same style connection, don’t seem to have this problem.

No idea why one would be better.

#11

Did you test this with a motor to see if it worked?

#12

Yes. The test data can be found here.

#13

No, test the new KOP Victor 888 that you were able to plug PWM into.

#14

If I read this correctly by the OP they say the Victors work with other forms of PWM source so to go to the next step.

Are the 3 power LEDs ALL on, on the digital side card?

Please make sure that the 6 volt jumper is removed on digital side car as well.

And one last thing, double check that the PWM cable is installed so that the grounds match.

#15

Yes, test results are here.

#16

*See attachment. It appears that some PWM connectors are more equal than others1.

Measuring how far the PWM protrudes is useful only if you you know the correct measurement for that particular brand/model of connector.

1 George Owell, Animal Farm

PWM.jpg
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PWM.jpg
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#17

I am a mentor for team 5196, and I think I might be able to clarify our issue a little more:

The female PWM connector on the VEX branded Victor 888 speed controllers on the 2014 KOP (I only specify this so strictly because I’ve never seen this issue on other Victors, but maybe I’m just lucky) seems to have a weak/loose connection when inserted straight up in the connector (and the plastic housing ONLY allows a straight, 90* insertion)

When we inserted the PWM cables (the NEW, UNUSED cables we got directly out of the KOP) into the victor, they were definitely going ALL the way into the female connector (you could feel that little bit of extra resistance as they slid in) and looked exactly like the picture you just posted.

They were, however, only giving us a flashing orange/yellow light which means “no PWM signal.”

At first, we thought we were getting no PWM signal from our DS, but connecting up a Jaguar as a test verified that we were, without a doubt, sending signal down that wire. We later ended up building a little PWM signal generator out of a spare arduino and verifying on a scope that it was, in fact sending signal before ruling out everything else except the speed controller itself.

After playing with the connector and trying to get it to detect the signal, we finally gave up and disassembled it.

We then hooked up the speed controller as normal, sans plastic housing, and inserted the PWM cable.

What we found was that the speed controller would only sense the PWM signal when the PWM cable was tilted a small amount.

This means that either

A. The PWM cable pins are too small and don’t properly make contact with the female connector

or

B. The connector is designed for larger male pins and doesn’t make a proper connection

or

C. The male pins on the PWM connector aren’t long enough to reach the bottom of the female connector on the victor

This issue occurred on BOTH of our KOP 888s, so I would guess that it’s either a manufacturing defect on the cables/speed controller OR FIRST gave us PWM cables with pins that were a little too small for the PWM connectors on those particular victors.

Our fix, as previously stated, was to insert solid 22 gauge wire into the connector (which was large enough in diameter to make a solid connection with the female connector in the victor) and put a female PWM socket on the other end of those wires.

#18

D. The shell often causes the PWM connector to not go in straight. The male pins end up missing the female socket entirely. The male pins deflect and end up resting beside the female socket, instead of inside of it. The male pins get bent slightly as a result, but it still “feels” like it went in completely, and correctly.

Pull the connector out, straighten the pins, and reinsert it part way. Wiggle the connector once you feel the pics hit the top of the female socket, but keep the connector absolutely straight. If everything is lined up right, it should actually take VERY LITTLE FORCE to insert the connector the rest of the way.

It may take a few tries to get it right.
This is also a very common issue. I have seen it 4 times already this year, and have lost count since I’ve started doing FRC…

#19

We verified this connection by shining a flashlight down the connector while we inserted it VERY slowly. We didn’t have any bent pins, either. Not even slightly.

However, I see your point. The Connectors kinda’ make it so you’re “going in blind” and makes it very difficult to get in properly.

#20

Question: Can only one CIM motor be attached to a Victor motor controller?