Operating a Spark MAX from a laboratory DC supply

FIRST General Forum
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This is for a non-FIRST application.

I want to operate a NEO, driven by a Spark MAX, using a laboratory DC supply to provide 12 VDC. My load will be relatively light except during starting, due to moment of inertia. By limiting the Spark MAX current I would like to stay under 20 Ampere DC during acceleration, and under 5A while the load is spinning at constant RPM.

My question for the community is, has anyone operated a Spark MAX from a laboratory supply? If so, what momentary surge current (before current limiting kicks in) should the supply be capable of? Using a battery in this application is not preferred, because it would introduce a non-standard workplace risk for the site.

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We have run plenty of spark max/neos on power supplies. Generally we try to use a supply that is 3x the current limit for what we are trying to do. You can get closer to 2x if you are sure to do slow ramping in either direction. We have a 60A supply and 200A supply that are mostly used for these purposes.

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Thanks, Greg.

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Could someone knowledgeable please clarify what type(s) of power supplies are appropriate vs. not? One can find an $85 12v 100a (supposedly) power supply on Amazon (people power CB’s with them), but I suspect using it to power a Sparkmax driving a Neo may not be a good choice.

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Pardon my ignorance, but what is a CB?

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Looks like the Solution is “Use a really big power supply”.

Appropriate power supply (for FRC applications) is one that doesn’t fold over during in rush and won’t overvoltage during recovery and does a pretty good job of voltage regulation.

The cheapest, easiest and most reliable that we have found is an FRC battery and a nice battery charger. As far as safety goes. Batteries and battery chargers see goofy loads all the time without a worry.

If you are doing dyno test/graphs or designing a motor then that’s a different story.

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Citizen’s Band radio was the way people talked to each other from moving vehicles, in the age before cellular phones.

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Breaker, breaker 1-9, you got your ears on?

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Ahhhh, a CB radio. Definitely know what those are, just didn’t know what it meant in the context of beefy power supplies and Spark MAX’s :sweat_smile:.

Thanks!

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And never forget their core plot significance in this little ditty!

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Back in the day, I used Sorensen DCS 20-50 power supplies to test CIM motors, fed by various FRC-legal controllers. As Greg says, that rating (20V, 50A) is probably still ok for some situations in the more recent, brushless world.

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I’ve had good luck with 600+ watt PC power supplies, especially 2010ish and newer as the 12V rail capacity increased. In the few times I’ve upgraded power supplies, I tie together all the 12V outputs (checking inside to make sure this won’t cause issues) and crimp them into an SB50 lug. I standardized everything at home to use SB50s for high current 12V, so that can get used almost anywhere along with various adapters floating around.

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A lot of server hotswap power supplies are 12v only and have a lot of capacity.

There is a community around hacking these and are really cheap on ebay.

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I was looking at purchasing some used server power supplies like this one to power the charger for an electric bicycle project. I think the one I linked is good for over 90A at 12Vdc out. That should give you lots of margin so it won’t trip out on a transient. What I read was that the fans for such power supplies are very noisy.

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