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I'm trying to figure out how to connect a vibration motor to my Arduino. I've come across this resource and it seems pretty straightforward though for a while my eye glazed over at how complicated the circuit was (do I really need all of that to run my vibration motor?).

My real question is that I have a vibration motor similar to the picture in the link and I'm trying to figure out how to actually connect it to my breadboard. Do I have to solder wires onto those flimsy ends or is that a better way to get this to work?

Thanks!

  • What application do you need it for? I've seen vibration motors employed as regular motors to drive a tiny worm drive. – vsz Apr 5 '16 at 4:46
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Lets break down the circuit and have a look why everything in that circuit is there and what it does.

First we have the 33R resistor before the motor which limits the current to the motor. This particular motor is rated at 75mA and has a starting of 85mA. The 33R resistor limits the current to 130mA maximum through the motor. If the risk of the motor pulling too much current is an issue then stick a fuse in-line

Then there's the motor, not much to say here really. It's whatever motor you're using.

We then have both a diode and a capacitor across the motor. I find this a bit strange, I've seen the use of flyback diodes, I've seen the use of snubbers, but both? The purpose of the diode is to allow a return path for any spikes caused by switching off power to the inductive load (the motor) which stops them from damaging the transistor. For the capacitor, just remove it, it's not got any use here really.

Then comes the transistor, it might be easier to think of a transistor as a switch (especially in this example). When you put a little bit of current on the base, the transistor 'opens' allowing the motor to connect to ground. The reason we have to use a transistor is because the outputs of an arduino are only able to supply a maximum of 40mA, we need more than that to run our motor. Fortunately, the transistor is not going to need any more than 5mA on it's base which is why we use it to 'switch in' components that require more voltage/current. The 1K resistor on the base is to limit the current coming from the arduino and preventing it from killing our poor transistor.

tl;dr - You need everything except the capacitor

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There are actually a number of things wrong with that circuit.

First the motor runs from 2.5 to 3.8V, yet they show it running off the 5V supply pin.

Secondly they include a 33Ω resistor to "limit the current". It doesn't! It drops a voltage depending on the current flowing through it, and the current flowing through it depends on the speed and load of the motor at the time. So the motor itself will be getting a fairly random voltage applied to it, which at times will be below the specifications.

E.g.:

  • The start current is 85mA. V=RI, 33*0.085 = 2.805V. 5 - 2.805 = 2.195V: way below the 2.5V required minimum.

  • The run current of 75mA calculates as: 33*0.075 = 2.475. 5 - 2.475 = 2.525V: only just enough for it to run.

So it should be powered from a 3.3V supply that has enough current capacity to drive it (85mA) and the 33Ω resistor should be removed entirely.

  • I'm really grateful for your answer. I've been doing nothing but LEDs for so long I'd fallen into a trap and completely forgotten something so basic. Thanks for waking me back up – Doodle Apr 5 '16 at 12:56
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I've never used a vibration motor, but I think you do need all of the circuit. Its says in the text, but the transistor is needed because the Arduino 'doesn't supply enough current through the output port' and the diode and cap are required to prevent spikes.

As to the flimsy wires you could solder them onto a bit of strip board and then solder "proper" wires of connectors onto the board too.

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You could make a simpler circuit by removing the diode, capacitor. BUT this comes at the cost of having a circuit that could kill your arduino.

Stick with it and build the entire thing. This isn't a shortcut worth taking.

  • I wouldn't even give the suggestion of removing the diode. It's general practice to always put a diode across an inductive load. Unless you like dead transistors – Doodle Apr 5 '16 at 10:46
  • I didn't say it was a good idea. Only that it was possible. – user2702772 Apr 5 '16 at 11:40

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