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Right now I have a bunch of motors (in blue on the diagram) that I believe are connected all in parallel. I tried hooking them up to the Arduino (3.3V-red and GND-black), but can't seem to get the motors to run. I think it might be a current issue but am not completely sure. The motors can only take 3.3V and I think they need a minimum of 230mA to run (I attached a picture of the motor information if needed). Is there a way that I can increase how much current that I am putting into the circuit? Or is there another issue aside from current that is preventing the motors from running? I was thinking about using capacitors but don't know how to include them in the circuitry. I'd prefer to keep the configuration in parallel for the practical purpose of the rest of the motors working if one decides not to.

Any help would be greatly appreciated! Please also let me know if you need more background information! This is my poorly made circuit drawing This is the information provided for the motors

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  • \$\begingroup\$ Duplicate question: electronics.stackexchange.com/questions/354808/… You are correct. Issue is current. The MCU pins provide voltage but little current so you need to use it to drive a transistor or transistor-relay combo so they act as a switch for a larger current. Similar to how your tiny little finger can open and close a dam by pushing a button. The reason you can't use just a relay is that the relay coil requires more current than the MCU can output so the transistor is used to switch the relay coil. \$\endgroup\$
    – DKNguyen
    Commented Apr 4, 2019 at 22:40
  • \$\begingroup\$ What is the maximum number of your motors that would start at once and run at once during intended operation? \$\endgroup\$
    – K H
    Commented Apr 4, 2019 at 23:25
  • \$\begingroup\$ why would you even think of using the arduino as a power supply? \$\endgroup\$
    – jsotola
    Commented Apr 5, 2019 at 3:50

2 Answers 2

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26 motors x 0.68A(start) = 17A if using 3V, allowing 10% drop from 3.3V means the driver RdsOn is 0.3V/17A <= 176 mΩ.

It also means your power supply can deliver 17A @ 3.3V or has a Supercap with 100ms start time, with dV/dt=0.3V/0.1s=3=Ic/C so for 17A C=17A/3 =~ 6 Farads with ESR ~ < <<100 mΩ such as this but now you need to regulate the charge current.

Back to the drawing board on what you really need to do.

Arduino drivers are 25~50 Ohms.

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If I count right here, you have 26 motors that each require 680mA to start. This is far, far beyond what can be supplied by the arduino's on-board regulator.

The regulator on the arduino board varies depending on type and manufacturer, but as the arduino doesn't consume that much power it's reasonable to assume it might use a cheap 78xx or LM1117-x, both of which can't provide more than about one amp. You're asking that poor regulator to give more than seventeen times its rating! You need a much higher current power supply to have any hope of starting all these motors at once. Even running them all at once takes over six amps.

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