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I was hoping to use this mosfet shield to control a "Standard 3528 12V LED strip". The shield looks like this:

enter image description here

However, it doesn't come with a datasheet (I guess that's my fault for being cheap) and now I'm confused about how to connect this to my Arduino Nano / Wemos D1. The black connector has +, - and s on the bottom but both blue connectors have no labeling whatsoever. So I'm not sure how to connect it to the 12V and Arduino. I've googled but haven't been able to find any documentation on this shield other than lots of sites offering it and with the same (or similar) pictures but never with any labeling. Maybe these things are so common that 'everybody knows' how to connect them?

The MOSFET is an IRF540. Also; I've read somewhere that I may need a transistor or "driver" to get the MOSFET to switch?

I have relays lying around and they work fine for my purposes but I was hoping to switch the LED strip without the noticeable click of a relay, so that's why I was looking into this MOSFET. (I also have some solid state relays laying around, but they're for AC).

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  • \$\begingroup\$ Buying EE stuff that doesn't have a data sheet isn't being cheap because it's likely you won't get the best performance without reverse engineering it to understand it and this costs more (time is money etc.) than buying the right goods in the first place and saving everyone's time who reads this post. \$\endgroup\$ – Andy aka Nov 6 '18 at 16:15
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    \$\begingroup\$ The sloppy placement of the components is not making me optimistic about this board. \$\endgroup\$ – Elliot Alderson Nov 6 '18 at 16:24
  • \$\begingroup\$ That power mosfet is literally touching the connector to the microcontroller and defeating the protection of the optocoupler... I would advise not using this board, it looks like something designed by a beginner who didn't know what they were doing. \$\endgroup\$ – Hearth Nov 6 '18 at 17:17
  • \$\begingroup\$ Get in touch with the supplier and ask for documentation rather than just complain about the lack. I'm sure the supplier has had to deal with question on the connections if they are not marked. The board is however simple enough you could trace the circuit easily. \$\endgroup\$ – Jack Creasey Nov 6 '18 at 17:19
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    \$\begingroup\$ I pointed out myself I probably shouldn't have so cheap; no need to point it out again and it's not helpful in any way. I know the board doesn't look great in the photo; my actual board(s, I got 4...) look much better. I can try to contact the seller but I have a feeling that's not going to get me far (again: shouldn't have been so cheap). HOWEVER; this is all I currently got lying around. I don't have drawers and drawers full of this stuff. Is there anyone that can help me figure this thing out (bootleg or not), even if it's only to see if I can get it to work? @Felthry: I got 2 of those too… \$\endgroup\$ – RobIII Nov 6 '18 at 17:25
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I found a different supplier with a clearer view of suspiciously the exact same board. Looks like the input feeds into an optocoupler, allowing the load side supply to pull the gate high. There's a non-switched positive input on the control side that seems to be there only to allow an LED to indicate that the control input is on. Should work without that connected though.

The output side is then entirely isolated and has two power connections at the top terminal block, the positive is commoned to the load block, and the FET switches the low side. enter image description here enter image description here

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  • \$\begingroup\$ Thank you very much. I assume your opinion on the shield is just as bad as the others? Besides the MOSFET (almost) touching the connector (I figured I'd just bend it up vertically), is it badly designed components-wise? If I'd had to have done it myself I would've added just the MOSFET in the circuit, maybe an optocoupler. I have no idea about gate clamps, freewheeling diodes etc. But I'm just a hobbyist fooling around with (simple) DIY projects. \$\endgroup\$ – RobIII Nov 6 '18 at 23:34
  • \$\begingroup\$ You won't be able to bend it up, the tab is one of the connections and will be soldered to a pad beneath. It doesn't look to be a bad design functionally, but the placement of the components, not just in assembly, but in the layout of the PCB, is not good. \$\endgroup\$ – Phil G Nov 6 '18 at 23:41
  • \$\begingroup\$ Again, thank you very much. I appreciate your feedback. As a final question then, maybe... Would you use this board for a simple project or is it a fire-hazard or something? I guess what I'm trying to say (English not being my native language): are the complaints about the bad placement because of actual danger or more of a theoretical "it should've been done such-and-such" nature? Oh, and will I be able to drive the board straight from a microcontroller liker a Wemos D1 / Arduino or would I need a transistor / "driver" I read about somewhere? \$\endgroup\$ – RobIII Nov 7 '18 at 0:29
  • \$\begingroup\$ The isolators only take 5-10mA to drive, so the Arduino should be able to drive it directly. As for hazard, you'll have to inspect the board carefully and ensure that there are no solder bridges, components too close or bad joints. It looks like the surface mount components are reflowed on, so the joints should be predictable. \$\endgroup\$ – Phil G Nov 7 '18 at 14:44

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