CIM Motor Capacitors

[ProgramLuke]

Where is a good place to buy capacitors for the DC CIM Motors allowed under:

A one microfarad (1 μF) or less non-polarized capacitor may be applied across the power
leads of any motor on your ROBOT (as close to the actual motor leads as reasonably
possible)

[RyanN]

Originally Posted by ProgramLuke

Where is a good place to buy capacitors for the DC CIM Motors allowed under:

Locally? A Radio Shack. You may be able to find another electronic component store near you as well.

Online? Mouser, Digikey.

May I ask why you're doing this. Nothing wrong with it, but I'm just curious if you're having problems with the cRIO or the Dlink bridge cutting out.

[Al Skierkiewicz]

Luke,
I know that many teams do not think of moving the motor controller closer to the motor it controls but this is a good way to reduce motor noise and allow the motor to be connected directly to the controller without having to add wire to the motor. The CIM motor has not been known as a noise producer as compared to the FP for instance.

[ProgramLuke]

Originally Posted by RyanN

May I ask why you're doing this. Nothing wrong with it, but I'm just curious if you're having problems with the cRIO or the Dlink bridge cutting out.

We are indeed having issues with communications. We are using all 4 CIMS on our drivetrain but if we don't have a battery that idles around 13V We lose comms if we try to accelerate quickly. What happens is that the Dlink drops out and we have to wait for it to restart to get communications. Are other teams having issues like this and do you have any solutions?

[DarrinMunter]

Do you have the power converter (12v in, 5v out) connected to the 12v output at the bottom of the PD board? And then the 5v from the converter feeds the radio.

[ProgramLuke]

Yes the Dlink is powered by the converter.

[billbo911]

Originally Posted by Munter2081

Do you have the power converter (12v in, 5v out) connected to the 12v output at the bottom of the PD board? And then the 5v from the converter feeds the radio.

Originally Posted by ProgramLuke

Yes the Dlink is powered by the converter.

Luke,
Darrin's specific question included "Do you have the power converter (12v in, 5v out) connected to the 12v output at the bottom of the PD board?" for a very good reason.
If it is connected there, the regulator in the PDB will provide +12vdc even when the battery voltage dips below +12vdc. If the converter is not connected there, but is connected to the standard Wago connections, you will loose the +5vdc out of the converter when the voltage dips.

So, do you have the power converter (12v in, 5v out) connected to the 12v output at the bottom of the PD board?

[ProgramLuke]

Thanks for the guidance. We had it coming out of the PD through a regular circuit. We will get that changed right away and see if it makes a difference. Really hoping this is the issue.

Thanks again!

[DarrinMunter]

Originally Posted by ProgramLuke

Thanks for the guidance. We had it coming out of the PD through a regular circuit. We will get that changed right away and see if it makes a difference. Really hoping this is the issue.

Thanks again!

We did the same thing two years ago! We were at the BMR, when a mentor from WildStang help us out.

[Al Skierkiewicz]

Originally Posted by Munter2081

We did the same thing two years ago! We were at the BMR, when a mentor from WildStang help us out.

Me?!?

[DarrinMunter]

Originally Posted by Al Skierkiewicz

Me?!?

It was Raul,
He said that he seen a couple of teams make the same mistake.
Blew us away, because everything was working on the test frame. When we moved everything over to Lunacy robot some how that got changed.

Lesson 1: Move over stuff one thing at a time.
Lesson 2: Take picutes before hand. Use them as a reference.
Lesson 3: Labels! What to where.


You can learn a lot from making mistakes - even more from fixing them.

[RyanN]

Originally Posted by ProgramLuke

Thanks for the guidance. We had it coming out of the PD through a regular circuit. We will get that changed right away and see if it makes a difference. Really hoping this is the issue.

Thanks again!

Yep, that's the main issue. The 12V coming out of the bottom of the PD board is a boost circuit. It is supposed to operate down to a battery voltage of 4.5V.

http://usfirst.org/uploadedFiles/Rob...tion_Board.pdf
Page 6 of 10.

[caffel]

This is a great thread.

I'd like to add a note that 1712's and several others converters 12v - 5v for the Dlink, failed.

It failed by providing only 4.1 volts.
Once you have tried all of the above advice, try tracking the 5v in at the Dlink and make sure its OK all the time.

Dropouts are happening in other areas of the robots this year and they are hard to diagnose, so look at the threads on Jaguars and encoders next as well.

[caffel]

One thing I learned early on, in robotics what you get is what you don't see.

Use meters to reveal things.
Voltage is easy.
DC Current is thought to be hard, but check out the Kussmaul Electronics 091-8 strap on ammeter. (inductive ammeter)

If you are overloading the main or subcircuits, this will pinpoint the problem for less than $20 and without disconnecting any wires.

Snap-on Tools has similar meters, but they are pretty expensive.

[DarrinMunter]

I found a PDF that shows how and where the converter gets connected.