The boards have arrived! I only have enough mosfets for one motor right now, but that’s all I need for testing. I’ll order a bunch if I can ever make up my mind which ones to buy.
Anybody have an opinion whether I should use 30V or 40V mosfets with 24V power supply? The difference in resistance is about double, but still half that of my old friend SE3082G. 1.2mOhm for the 30V JMSL0302AU-13, 1.7mOhm for 30V BSZ0901NS (same ones used on Antun’s DriveShield), and 2.7mOhm for 40V AGM403AP.
I think the SMM4F26A TVS diode from ESC1 can only protect the 40V ones since it breaks down at 28.5-31.5V, and is still not 100% safe with 42V clamping voltage. But I think ESC1 has 35V ceramic capacitors, so maybe that’s ok? The next lower SMM4F24A looks like it would provide some protection for 30V mosfets while still being (I think) safe to use at 24V supply voltage, but would need 40V mosfets for full safety with 39V clamping voltage. And still not fully safe unless I use 50V capacitors, which I’d rather not since they’re huge. 35V can fit two 470uF per motor bent down over the mosfets, whereas 50V would need one big one per motor on the back side of the board to avoid blocking either the connectors or motor wire pads. Maybe 50V ceramics and 35V electrolytics would be safe enough? On the theory that the ceramics will charge up quickly, but the electrolytics will suppress typical transients before charging above 35V. But maybe something like a hoverboard motor could still kill them.
I’d also appreciate any opinions on the JMSL vs. BSZ0901 for <18V applications. JMSL is marginally better in terms of resistance and price, but Infineon is a more well known brand and it feels like a waste not to buy them while they’re on sale. Maybe I’ll just get some of each.
