VexAI power connector

@levipope

Can we get clarification on why there are two connectors on the v5 brain side for sending power to the jetson? Maybe a schematic of the connections too. I assume it’s functionality is to increase current capability (meaning the wires are in parallel). Thanks.

@JusticeLeague5233J

You are correct. We use a parallel connection for both power and ground to better distribute the current load on the 3-wire ports.

Thanks
Levi

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Is there a fuse on each individual port or just a shared fused on all the 3 wire ports together? Or is the goal to share current to protect the wires / pins?

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@tabor473

There is one fuse for all of the 3-wire ports. So the double wire was just to protect the wires and pins/connectors.

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@levipope Feedback on powering the Nano module.
First thing we did was power the Nano using a buck converter and surplus 7.2V NiMH batteries (got a few of those lying around). Ran the Nano at full power rather than 5W mode.
Two 7.2V battery connections were used so we could live swap during development without rebooting the Nano. Controlled shutdown of the Nano was also a consideration.

In essence we weren’t happy with powering from the 3 wire ports for multiple reasons. Runtime from a V5 battery wasn’t adequate.

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Are we the same person? 2 7.2V batteries to allow hot swapping is how I powered by jetson years ago. I also had an inline power monitor just in case it was useful.
IMG_20210322_142333

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Nope, we diode isolate the batteries and use Anderson Power Pole connections. And a much cooler buck/boost module with input and output VI monitoring :wink:

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@wdr_mentor

What y’all are doing sounds great. We created the power adapter for the V5 to keep things simple and not require an extra battery for matches. In low power mode the you should easily be able to run of a single V5 battery for the length of a match. But I 100% agree that it does make it a little more difficult for development. I will note that if you run the Jetson in the 5W mode you can work on a stationary robot for an extended period of time if you leave the charger plugged into the V5 battery. But testing on a field does require a lot of battery swaps. The only thing to watch out for, running at full power, make sure you have adequate air flow on the Jetson. That baby can get hot.

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Understand the need for simplicity. Just providing feedback that simplicity didn’t work for us and hot swapping was an important consideration. If you’re just using the Jetson Nano as a black box VEX sensor then the supplied power cable would be okay.

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See my girlfriend (ECE major then, and now ECE PhD student) promised it would be fineeeee. Okay actually she said I needed to ensure a fully charged battery and a depleted battery were only both plugged in for short periods of time. For extended use the two batteries needed to be very similarly charged otherwise directly connecting them would cause the more charged of the pair to try to discharge aggressively until the charge was equalized. We made sure to always swap both together, one after the other.

(I realized I should actually explain what is required to mimic my picture without obvious danger)

Diode isolating of course removes that risk.

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Lol, she is right, it’s all going to be fine…

If the batteries are not new and have had many charge discharge cycles, then their internal resistance grows and that would limit the current of energy transfer while you swap them.

You only going to run into problem if batteries are new or you leave them connected for long period of time - then they will overheat and damage to electrodes will occur.