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I have 4 24v DC motors that I would supply with a 24V 5A AC adapter I have 2 L289N motor driver board though so I wont be connecting them directly to the adapter.

Question: Is it safe if I power the 4 motors with just 1 adapter?

The motor's current draw (running current) is about 0.1A each so I figured it would be enough for it to power but I've read somewhere that unregulated power supplies (im not sure if this one I got is regulated or not) are unreliable to power motors especially because the current draws may vary because each motor I use will not work simultaneuously (e.g. at a time, only 1 or 2 motors are running, 2 are dead or 3 are running 1 is dead and all 4 may be running at the same time)

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With an unregulated power supply, the voltage will vary with the current draw. Motor speed is proportional to voltage, so any given motor will experience speed variation according to the current draw of the other motors. When each motor is switched on, it will draw a higher current than the normal running current. Depending on the motor design, that current could be much higher than the normal running current. With the very small motors described, the high current will likely be very brief and not extremely high. Even with brief surges of current, the speed variation of the other motors may be noticeable.

If the power supply has electronic over-current protection, switching-on motors may cause the power supply to shut off or cut the voltage to protect itself.

If the power supply has enough capacity and speed variations are not a problem, switching several motors on and off should not be a problem. The voltage in a car is not particularly well regulated, but the supply has a large capacity. The many motors for fans, windows, seat adjusters etc. turn on and off with no difficulty. However the voltage drops considerably and the lights dim if the starter motor is operated with the lights on.

I missed the mention of motor driver, one for each motor I assume. With proper use of the motor drivers, any change in the supply voltage due to varying load or raw input supply voltage can be compensated for. Attempting to accelerate a motor too quickly or overloading a motor could still shut the supply down.

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  • \$\begingroup\$ If I understand this correctly, this means that it is not recommended to power the motors with an unregulated power supply directly but if I use a motor driver then it will be fine. Also, I would also like to mention that I will be using 2 motor drives as the motor drivers can drive 2 motors. I'll add the link for my motor driver. Thanks a lot! \$\endgroup\$ – John Michael Garcia Aug 29 '18 at 6:25
  • \$\begingroup\$ You provided a link to the eBay listing for the motor driver. You really need the manufacturer's specification sheet. The listing calls it a stepper-motor driver for Arduino, but also calls it a dual H-bridge. I expect that the Arduino can treat it as two independent H-bridges driving two independent motors. With the proper programming, should work fine assuming that the drivers are adequate for the motors. An unregulated supply and on/off switches is fine for multiple motors if the supply capacity is adequate to handle the current draw of stalled motors. Motor performance is impaired some. \$\endgroup\$ – Charles Cowie Aug 29 '18 at 10:13
  • \$\begingroup\$ Sorry about that. I cant really find a proper documentation for the board so Im going to provide the a link for the L298N instead. The running current of my motors is about 0.1A and Ive read somewhere that I can assume the starting current to be about 10x the running current, so 1amp per motor. The motor driver indicated a peak current of 2A per channel so I think it's adequate for the motor. It seems that the Last thing I have to check is the stall current. \$\endgroup\$ – John Michael Garcia Aug 30 '18 at 2:53
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The switching power supply is designed to power constant current LEDs, not the wildly changing current of an electric motor. It will probably shut down the moment one of your electric motors start.

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    \$\begingroup\$ You are alluding to a real concern, but the way you are stating it is not really accurate. Switching power supplies do well with varying currents (and in fact controllable LEDs have widely varying current draw). However, there is a legitimate question of startup (and also stall) motor current. Since H-bridge drivers have already been mentioned, startup can often be mitigated by ramping up the drive in software. \$\endgroup\$ – Chris Stratton Aug 25 '18 at 15:12

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