I am trying to control a brushless dc motor. I have a H-bridge style MOSFET circuit and am controlling the gates with an Arduino. However I am trying to power the motor with a 7.4 V lipo battery (which is required by that motor). The MOSFETs are also high current rated so shouldn’t be an issue (linked here https://4donline.ihs.com/images/VipMasterIC/IC/ONSM/ONSM-S-A0003584711/ONSM-S-A0003584470-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0). But when I connected the battery to the circuit it all started smoking. Is there something obvious I'm missing- I hadn't started the Arduino program yet so none of the MOSFETs should've been 'open' so no current should've been drawn. I am aware that a breadboard and breadboard wires probably arent suitable for the current levels but seeing as the motor wasnt connected at this point (was just trying to test the MOSFET circuit) I don't see how that could've been the issue. On that note does anyone have any advice on how to test a higher current circuit like this if breadboards don't take that much current.

Motor: https://www.amazon.co.uk/dp/B075731ZJM?psc=1&ref=ppx_yo2ov_dt_b_product_details lipo battery: https://www.amazon.co.uk/dp/B08JCM7HBH?psc=1&ref=ppx_yo2ov_dt_b_product_details The numbers in the picture are connected to arduino pinsenter image description here

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    \$\begingroup\$ Piece of advice: NEVER connect a battery (especially a high power Lipo) directly to a circuit you are testing. Use a current limited power supply, or if you don't have one a low voltage incandescent light bulb (eg. 12V 6W) in series, which will increase resistance to limit short circuit current and light up to tell you. DIY brushless motor controllers are particularly prone to 'opening' when they shouldn't while being developed. \$\endgroup\$ Jul 17, 2023 at 10:40
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    \$\begingroup\$ Please draw a full circuit diagram showing all connections, and if you can a photo of the setup. \$\endgroup\$ Jul 17, 2023 at 10:42
  • \$\begingroup\$ Thank you. Apparently the motor max current is 27.6A, had a quick look at DC power supplies but they all seem to be much lower current? \$\endgroup\$
    – io19
    Jul 17, 2023 at 11:16
  • \$\begingroup\$ If you can’t get the motor running with a lower current, it won’t work any better with a higher current. Best use a power supply and avoid the smoke first. Then go to a battery. You circuit will not work as is. Find yourself an ESC and see how their circuit is arranged. There’s also plenty of open source projects to work from so you can avoid designing from scratch. \$\endgroup\$
    – Kartman
    Jul 17, 2023 at 11:30
  • \$\begingroup\$ should've been 'open' so no current should've been drawn. ... please use the word conducting because open usually means not conducting \$\endgroup\$
    – jsotola
    Jul 17, 2023 at 15:43

1 Answer 1


From your description, I'm guessing that you are connecting each gate directly to an arduino output (if not, please provide full schematics).

If so, you should know that when the gate of the mosfet is not driven at all (ie not connected, or connected to an arduino pin configured as input, ie high impedance), you have no way to know the state of the mosfet : it might be conducting, blocking, or somewhere in between (it depends of the charge of the internal gate-source capacitor). So without any additional components, it is possible that both top and bottom mosfets where conducting at the same time, creating a short circuit.

If you care about the "default" state of a mosfet, always add a pull-down or a pull-up resistor (in your case, I would recommend a 100k pull down resistor for each gate).

Note that there are many other possible problems, but those depends on the exact circuit/setup. pictures of your (burned) setup might also help


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