THE HORROR! THE HORROR!

[Kevin Sevcik]

Originally Posted by Tom Line

This is almost always a failed cell in the battery - or many failed cells.

We use the West Mountain battery tester to test our batteries. We found several this year that had normal voltages initially, checked good on our battery beak, but fell off after 5-10 minutes of testing fairly sharply.

On the one hand I want one of these. On the other hand I don't want to spend the money. Maybe I'll spend some time this offseason working out some software to use a Black Jaguar and some power resistors as a poor man's version of this.

[Ether]

Originally Posted by Kevin Sevcik

Maybe I'll spend some time this offseason working out some software to use a Black Jaguar and some power resistors as a poor man's version of this.

Hmm. You've got me curious. Can you give a general idea of what you have in mind? Is the purpose of the Jag to allow you to record data (via CAN) and shut off automatically so you don't have to babysit it?

[Kevin Sevcik]

Originally Posted by Ether

Hmm. You've got me curious. Can you give a general idea of what you have in mind? Is the purpose of the Jag to allow you to record data (via CAN) and shut off automatically so you don't have to babysit it?

Black Jags are serial controllable and have current control modes plus built voltage and current feedback. So all you would need for a battery tester is a serial port (or USB-Serial adapter), a serial to Jaguar adapter, a Black Jaguar that most every FRC team has 1 of, and a power resistor you can get at Mouser or your local electronics surplus store. Battery on the input side, power resistor on the output side, tell the Jag to dump X amps into the resistor, then record and plot your feedback. Primary difficulty is making the program to control the Jaguar. Either I'd need to figure out how to generate the FRC heartbeat, or you'd have to flash the Jag with custom firmware.

[Alan Anderson]

I remember one work session where a robot decided to "spin out" as soon as it was enabled. It did not respond to any control inputs. The cause turned out to be a disconnected gamepad. Pressing F1 on the Driver Station brought things back to normal.

[Ether]

Originally Posted by Kevin Sevcik

I'd need to figure out how to generate the FRC heartbeat.

Is that documented somewhere, or would you have to put a sniffer on the line to analyze the traffic?

[Kevin Sevcik]

Originally Posted by Ether

Is that documented somewhere, or would you have to put a sniffer on the line to analyze the traffic?

I have no idea. I've put zero effort into the project at the moment. I've run serial sniffers before for various work projects, so I have a reasonable idea how to go about it. I'm hoping it's actually just documented somewhere, though.

[Radical Pi]

Originally Posted by Kevin Sevcik

I have no idea. I've put zero effort into the project at the moment. I've run serial sniffers before for various work projects, so I have a reasonable idea how to go about it. I'm hoping it's actually just documented somewhere, though.

If you roll your jaguar back to the factory firmware (available at the bottom of VEX's product page), the "trusted mode" heartbeat isn't required. Last I heard, the trusted mode stuff isn't documented to prevent people from replicating it (the code is in the closed-source NetworkCommunication library. Security though obscurity I guess). AFAIK, the factory firmware is functionally identical to the FRC one, minus the heartbeat.

You can also find the source code for a slightly older version of both the factory firmware and bdc-comm in TI's RDK-BDC24 package. I have no idea whether VEX plans on making a similar release with the newest code.

[Team23pitboss]

Originally Posted by Kevin Sevcik

Black Jags are serial controllable and have current control modes plus built voltage and current feedback. So all you would need for a battery tester is a serial port (or USB-Serial adapter), a serial to Jaguar adapter, a Black Jaguar that most every FRC team has 1 of, and a power resistor you can get at Mouser or your local electronics surplus store. Battery on the input side, power resistor on the output side, tell the Jag to dump X amps into the resistor, then record and plot your feedback. Primary difficulty is making the program to control the Jaguar. Either I'd need to figure out how to generate the FRC heartbeat, or you'd have to flash the Jag with custom firmware.

Wow, that is an absolutely brilliant idea I think that our electronics guys would probably be interested in trying something like this out at some point. It also give me something to do with all the ancient computers with serial ports I have floating around my house.

[Ether]

Originally Posted by Team23pitboss

It also give me something to do with all the ancient computers with serial ports I have floating around my house.

You can turn those ancient computers with serial ports into test equipment, like for example a poor-man's logic analyzer to inspect the timing of digital signals like encoder pulses. Or DIO set by tasks to inspect scheduling timing and jitter.

[Team23pitboss]

You can turn those ancient computers with serial ports into test equipment, like for example a poor-man's logic analyzer to inspect the timing of digital signals like encoder pulses. Or DIO set by tasks to inspect scheduling timing and jitter.

I recently turned an old PCI-X sound card I had in an old gateway into a low-voltage oscilloscope and it happens to have a built in mic input and radio antenna so I can analyze radio and sound frequency as well (if I ever have the time to really muck around with it). I have never actually used a serial port for anything so my lack of familiarity could be a bit of a hindrance as far as creating makeshift equipment is concerned, but maybe over the summer...

[Chris is me]

In the two regionals I've attended so far, I have only ever seen one robot lose comms. I didn't watch every match, but it's been one of the best years for this sort of thing since 2009 in my experience.

[Kevin Sevcik]

624 was having comms problems at Lone Star, but they definitively tied it to a radio reboot under heavy current draw. Unfortunately, they've swapped out everything, sometimes twice, in their attempts to fix it. I know they were fine in their last quals match, but I don't know if that stayed that way during the elims.

[Ether]

Originally Posted by Team23pitboss

I have never actually used a serial port for anything so my lack of familiarity could be a bit of a hindrance as far as creating makeshift equipment is concerned, but maybe over the summer...

Borrow Jan Axelson's book Serial Port Complete at your local library. It will get you up and going in no time.

If your local library does not have it, use inter-library loan to get it.

Or buy it.

The demo code and code examples downloadable here show how to read and write some of the RS232 control pins, and how to read the Pentium's RDTSC 64-bit nanosecond timer.

[Ether]

Originally Posted by Team23pitboss

I recently turned an old PCI-X sound card I had in an old gateway into a low-voltage oscilloscope

I'm running Lucid Linux with Xoscope and Osqoop on a Gateway PA6. All you need is to download the Lucid Live CD ISO and burn it and boot from it, then get online and download the scopes.

The trickiest part (but hardly difficult though) is to make a small passive circuit with caps and resistors to divide down the signal voltage and block the mic DC power coming out of the laptop mic port.

It will work with just about any reasonable signal voltage, given the appropriate voltage divider. The limitation is the 96KHz sampling frequency. The upside is that it will store hours and hours of data (limited only by available disc space).