On-Board Battery Checker

VEX V5 General Discussion General Forum
1

Will this On-Board Battery Checker from lynxmotion work with the vex?

http://www.lynxmotion.com/Product.aspx?productID=463&CategoryID=48

It says its Plug and Play, I’m not sure if its Lynxmotion products only.

2

Well for one you would need a female to female connector to even be able to hook it up to the VEX brain. As far as whether or not it would work I have no idea.

3

I have one and it works well. I took two header pins to allow it to plug into the controller.

It’s not Vex legal in a match, but it does work well in seeing how battery life is going.

4

Do you plug it into the analog/digitals or the motors, or interrupts?

5

It can go any place that has voltage available to it. I’ve been putting it in the last digital/analog slot to keep it out of the way.

6

The voltage provided on the I/O and Interrupt ports is regulated to +5VDC, so if you plug it in one of those ports, it’ll see 5V constantly until the battery has dropped down to around 5.5V and the regulator can no longer keep up.

For this to provide a descending reading as the battery discharges, you’ll need to plug it into a motor port. You can attach it via a Y cable to avoid loosing a motor channel.

Cheers,

  • Dean
7

so is this why whenever my battery is low my sensors don’t work?

8

Now would that only show when the motor is running?

9

It shouldn’t be. The voltage regulator is there to prevent exactly that. It puts out a steady 5V to the PIC microprocessor and the digital/analog and interrupt ports regardless of battery voltage. Once the battery gets below about 5.5 volts, the voltage regulator can’t do its job perfectly anymore and so the 5V starts to fall off. This is what is called a “brownout” condition and it causes the PIC processor to reset. This is what is happening when the power LED flashes red periodically.

The battery V+ is constantly present on the center pin of the motor port connectors while the Vex Microcontroller is on. This is why you can plug VEXplorer accessories into the Vex Microcontroller motor ports and they will run/work continuously.

The PWM signal that controls the motors speed is just a logic-level signal and doesn’t provide any power itself. So, the three-circuit motor connector is two battery conductors to provide power plus one signal conductor to provide speed information.

Cheers,

  • Dean
10

I’ve been doing experiments on the “brown” out, based on the current robot and the motor loads, so I want the voltage to drop below where the PIC will reset. The big display makes it easy to see.

Dean is right, to follow full battery loads, plug it into the motor port.

Sorry to have confused the issue.

Foster