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I'm trying to power a 12v 5rpm DC motor using a 2ch relay board and some 18650s. I am also using a MT3608 boost converter and a TP4056 to make the whole thing rechargeable. I'm having trouble that when the direction of the motor is changed too quickly it causes the whole circuit to shutdown until I reconnect power. I believe it is something being triggered on the charging board, because when that is removed there is no issues. My questions is there a way I can circumvent this problem. I would imagine there is a much more efficient way to do this (and if there is please let me know), but this was just a small project I was working on with stuff I had laying around. Any help would be greatly appreciated!

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  • \$\begingroup\$ That's called flyback or inductive kick. \$\endgroup\$
    – DKNguyen
    Apr 23, 2021 at 19:32
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    \$\begingroup\$ Don't go "forward - reverse". Go "forward - stop - reverse". You'll get a massive kickback if the motor is still turning when voltage is reversed. \$\endgroup\$
    – Transistor
    Apr 23, 2021 at 19:51
  • \$\begingroup\$ Would a TVS diode help in this situation? I'm not worried about having to switch directions quickly, more so protecting the equipment and not having it shutdown because it will be controlled by remote. Thank you both for the quick replies! \$\endgroup\$ Apr 23, 2021 at 20:42

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i belive that you are using something like this diagram in your wiring , reverse motor

since you`re using 2 channel relays ,you have 4 states for the relays,

1- ch1 on ch 2 on => this will connect both terminals of motor to the dc which will result in hard breaking,

2- ch1 on ch2 off => this will run the motor clockwise/clock side based on your connection

3- ch1 is off ch2 is on => this will reverse the motor direction,

4- ch1 is off ch2 is off => this will turn off motor but it will not break, its like Neutral [N] gear in the car,

  • to move from state 2 to state 3 you should go through either state 1 or 4 , as flipping the status of relays is not instant, a voltage (Ve) will be genetrated in motor also due to mechanical movement, this will be addup voltage to the source (Vs) and so on it will be Vs+Ve and a spike will activate the protection in the MT3608 converter.
  • if your replaced the relays with a transistors (4 of them, 2 n type,2 p-type) you should make sure to let time gap between on and of state for each side so that the transistor leaking current get dumped, else as @transistor said , it will short the system,
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  • \$\begingroup\$ Would adding a TVS diode help in this situation? I'm trying to prevent it from completely shutting down as it will be controlled with a remote and having to go reconnect power wouldn't be ideal. Thanks for the detailed explanation! \$\endgroup\$ Apr 24, 2021 at 0:50
  • \$\begingroup\$ @ShaneDaily A TVS diode will help for sure , it will eleminate the generated voltage (Ve), but you should know where to put it else the TVS will be the shorted path, you can connect the TVS as this diagram :img, please do not mistaken the place of tvs to be around the motor as this section is changing in direction and 1 tvs will short the powerline in of one directions, you are always welcome! \$\endgroup\$ Apr 24, 2021 at 6:36
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    \$\begingroup\$ Awesome! Going to go do some research right now. Thanks for all your help I really appreciate it. \$\endgroup\$ Apr 24, 2021 at 22:29

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