Mastech HY3020MR Constant Current

[osteichthyes]

The user manual I found claims that you set it by applying a load. I interpreted that to be a short. Not sure why. I'll track down a load and report back. Manual attached.

[bitseeker]

2.2.2 Setting current limit: Take turns pressing ( I ) button (0~9 digital) button (ENTER) button, until
it to the voltage value needed. (Must connected load, The actual current limit value should be display.)

Apart from it saying "voltage" where it should say "current," at least it does say that you have to connect a load. However, the fact that you enter the limit value using the numbers on the keypad leads me to believe that you can set the current limit without anything connected.

Anyway, I look forward to hearing about your experience actually trying it.

[osteichthyes]

I belive its working as it should. Mostly. I tested it on an old hard drive (that I then bumped, shorted, and fried) and was able to control current. I think it's working as designed, but that design clearly requires a real load, not a short.

[bitseeker]

Sounds good. Thanks for the confirmation.

[Ordinaryman1971]

It may be overkill but you could also buy one of the electronic loads on ebay and then you could control the load somehow. They are not that expensive, last I've looked they were about $35 or so... I mean, this way you could vary the load and see if and when it goes in to CC mode.

[osteichthyes]

OK. I tracked down a few giant resistors and gave it a whirl. Fun fact, apparently our lab benches are painted with something that does not handle heat well.... Learned that the hard way.

Anyway, it turns out that if you set the current low and voltage high, it is current controlled. When you turn the current high and voltage lower, it is voltage regulated. It's just based on ohms law. So, I was able to test it up to around 3A, around 24V, and about 70 some odd watts. It seemed to work fine. I calibrated the current as best as I could without igniting our apparently flammable lab benches and now it's working!

I've also decided that for myriad reasons I don't need it and will probably sell it.

I haven't seen a $35 variable load. Do you have a link?

Thanks for the advice all, and I hope the documents I posted help others.

[bitseeker]

I haven't seen a $35 variable load. Do you have a link?

Price is generally proportional to watts of dissipation capability. Of course, higher-quality ones cost more too. You can buy one for as little as $10, but it's not much more than a transistor and a CPU fan/heatsink. The ones in the price range you specify are often used for testing power banks (i.e., LiIon batteries). Search eBay for electronic load. There's oodles of them.