Getting 3v motor to work with photon * 2n2222 transistor

General
1

I need some help controlling this hobby motor. I’m using the 2n2222 transistor, 1k ohm resistor, and a 1uf diode. I posted some pictures below. The motor only turns on if I have one to diode + and then one to ground. But inwant to be able to control it via the digital pad. Right now when I do get it to work it restarts the photon due to drawing too much power.

Any help would be appreciate.

Thanks

IMG_20161027_200801.jpg4000×2992 2.55 MB

IMG_20161027_200748.jpg2394×3200 1.75 MB

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@thrgk, pictures from the top are always better to see the wire alignment. Howerver, from the picture I see you are trying to power the motor using 3.3V from the Photon. Unless you have a very low current motor, this will not work. If the motor can handle 5v then power it from the Vin pin instead. Having a flyback diode is good practice and I also recommend adding a large electrolytic capacitor between Vin and GND near the transistor to help handle motor startup current. I suggest 100uF or so.

BTW, I suspect when you said a “1uf diode” you meant to say a 1N4001 diode instead :wink:

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3

Thanks for the suggestion. Using vin will I he able go control the motor though ? I need to be able to tell it to stop and start.

I’ll add the capacitor as well and yes that is what I meant when I said 1uf. Sorry he he and thank you

4

@thrgk, let’s review to make sure we are on the same page:

  • The motor side of the transistor which includes the motor and the flyback diode is to be powered from Vin.
  • The motor you have MUST be rated for 5v operation
  • The motor you have cannot draw in excess of 700ma (even though the 2n222 is rated for 800ma, let’s not take chances!)
  • The base of the transistor has a resistor connecting it to a GPIO pin on the Photon. This will allow the transistor to be switched via that GPIO pin. A HIGH on the pin will turn the transistor ON.
  • The base resistor needs to be selected so that enough current flows through the transistor to “start” the motor. This site is a great reference for using transistors as switches: http://www.ermicro.com/blog/?p=423

You will see your circuit there in one of the figures where Vcc in your case is Vin of the Photon. Have fun and let me know how it goes!

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5

Hmm my motor is a hobby motor 1.5 to 3v. I’m not sure of the ma as its not stated.

http://www.hobbylobby.com/Crafts-Hobbies/Kids-Crafts-Activities/Science-Educational/Small-Electric-Motor/p/25574

I did see this guide here, but would this not work with my motors ?

Thanks

6

@thrgk, the motor you selected is designed for a max of 3v so you cannot power it from Vin. The hackster project uses a 6v motor.

In order to use the motor you have, you could power the motor with 2AA batteries that give you 3 volts total. A battery holder is ideal for that. The +3V side of the battery holder would be Vcc to the motor and the other side of the battery (typically black wire) would connect to GND of the Photon/transistor combo.

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Ok so Put the + wire from the 2AA battery holder to the motor, put the - battery pack wire to ground on photon. I also put a wire from ground on photon to motor ? Should I still use any transistors? I thought I needed to have it go to Analog or Digital pads so I can control on and off?

Ill try to use paint to show what i mean.

Thanks for the help so far, really appreciate it. So hard to get this motor working

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@thrgk, all grounds need to be common - 2n222 emitter, photon GND, battery ground wire (black typically). The motor “ground” goes to the transistor collector only. Refer to the schematics in the blog I linked to in a previous post.

The transistor is there because the Photon pins can’t handle more than 25ma of current. So the GPIO pin drives the transistor base via a current-limiting resistor and the transistor acts as a high(er) current switch for the motor. The voltage it is switching is provided by the battery pack. The Photon still needs to be powered via USB. :wink:

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Ah so it cannot just be powered by the 2AA? As once I get it going I needed it to be wireless :frowning:

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@thrgk, so we went from getting a 3v motor to work with photon and transistor to “how do I control a motor with a photon and have the whole thing battery powered”!

That is a different problem and here is why:

  • The Photon can be powered from a 3.3v or 5v supply but NOT a 6v supply directly
  • The motor takes too much current to drive from the 3.3v pin and besides it a 3v max motor!
  • A transistor is needed to switch the motor on/off due to the current required
  • When the motor switches ON, the current from the battery will spike so the battery(ies) need to provide enough power for the Photon and the motor under these conditions

Before I can propose a solution, what kind of battery were you hopping to power all this?

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I currently have a couple of 18650 3.7v Lion batteries I was hoping to use

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@thrgk, the battries you want to use may or may not come with built-in under-voltage protection. If they measure about 69mm in length then they most likely have that protection. If not, then I don’t recommend using them without an under-voltage circuit (or breakout). I recommend you read the following project post for how to setup a great LiPo/Photon/Motor controller configuration:

https://www.hackster.io/bdub/particle-pokeball-36d914

You should also consider using the two batteries you have (assuming they have built-in protection) with this great Photon shield:

Here is the schematic as well:

https://github.com/simonmonk/PhoBot/blob/master/hardware/datasheet_1.0f.pdf

:smile:

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