Power a DC Motor Clockwise and Counter Clockwise with Raspberry Pi.

[Zonther]

I'm working on my final project and my professor will be out until finals are over. I am using 2N2222A NPN Transistors to power a DC motor to turn clockwise or counter clockwise.

I created a diagram of how I would think it will work bunt I don't want to build it and find out it blows something up. I haven't had any electrical engineering classes and this is a computer architecture class.

In a way this is the first I am creating my very own circuit and not just copying off from one of my labs.

I did not have a lab that worked with transistors or making a DC motor turn clockwise or counterclockwise.

 

If you can, please let me know if this will work or what I will need to change to make this work.

Edited April 19, 2023 by Zonther

[FI Fheonix]

6 minutes ago, Zonther said:

I'm working on my final project and my professor will be out until finals are over. I am using 2N2222A NPN Transistors to power a DC motor to turn clockwise and counter clockwise.

I created a diagram of how I would think it will work bunt I don't want to build it and find out it blows something up. I haven't had any electrical engineering classes and this is a computer architecture class.

In a way this is the first I am creating my very own circuit and not just copying off from one off one of my labs that she has us do.

 

If you can, please let me know if this will work or what I will need to change to make this work.

The 2n2222A NPN transistor can be used to power  a DC motor to turn counter-clockwise and clockwise. However, it is important to be aware that this transistor offers a constant DC collector current of 800 mA, so loads that use more than that power limit can not be connected using this transistor. Also, the transistor is rated for a 40v max so you won't be able to drive high voltage motors with this transistor.

[AbydosOne]

2 minutes ago, Zonther said:

If you can, please let me know if this will work or what I will need to change to make this work.

Off hand, it looks like it should work. Look up "H-bridges" if you want to confirm your design with other examples.

 

Couple words of warning:

• Don't power the motor directly from the RasPi; inductive flyback from the motor (i.e. motor momentum continues to create electricity after source is removed) could damage components on the board or the BJTs. Most H-bridge components have diodes across the BJTs to mitigate this.
• Make sure programmatically it's impossible to have both GPIO14 and GPIO15 on simultaneously or else you'll pull a (close to) dead short and blow up all your transistors. Many H-bridge chips have supplementary logic to prevent this (or to simplify the I/O to "direction and power").

[Zonther]

6 minutes ago, FI Fheonix said:

Also, the transistor is rated for a 40v max so you won't be able to drive high voltage motors with this transistor.

I am using 3-6v DC motor. Sorry I forgot to add that in my post. Thank you for your response!

[FI Fheonix]

2 minutes ago, Zonther said:

I am using 3-6v DC motor. Sorry I forgot to add that in my post. Thank you for your responce! I will test to see if that 800

I'm not really sure how well that will, work but good luck.

[Zonther]

Just now, FI Fheonix said:

I'm not really sure how well that will, work but good luck.

Thank you!

[FI Fheonix]

4 minutes ago, Zonther said:

Thank you!

Let me know how it goes...

[Zonther]

10 minutes ago, AbydosOne said:

Make sure programmatically it's impossible to have both GPIO14 and GPIO15 on simultaneously or else you'll pull a (close to) dead short and blow up all your transistors. Many H-bridge chips have supplementary logic to prevent this (or to simplify the I/O to "direction and power").

Ya that is what I will try to avoid. Thank you for bring H-bridge  up because I haven't heard of this before!

I was thinking

 

if button = pressed :

   while button = pressed:

       turn on GPIO 14

   turn off GPIO 14

 

 

[AbydosOne]

24 minutes ago, Zonther said:

I am using 2N2222A NPN Transistors

Actually after a little further research, making an H-bridge using only NPN transistors it probably not the right way to go (for EE reasons). Do you have access to PNP transistors as well? 

 

This is roughly the optimal configuration for an H-bridge: PNP on top, NPN on bottom.

 

 

2 minutes ago, Zonther said:

if button = pressed :

   while button = pressed:

       turn on GPIO 14

   turn off GPIO 14

Keep in mind that you won't be able to do anything else while you're in your button == pressed loop (including manipulate GPIO15). You might be better served with some state variables and setting your GPIO once all the logic is processed. Alternatively, I would recommend some sort of external logic to absolutely prevent that from happening.

[Zonther]

8 minutes ago, AbydosOne said:

Do you have access to PNP transistors as well? 

No I do not have PNP transistors. I will have to look up what EE reasons and H-bridge up to get a better understanding. Thank you for letting me know!

[OhYou_]

I would just use relays. you can literally buy a relay hat for a raspi. 
it just drops on and then you should be able to figure out from there how to wire it so that you can enable a set of relays for the desired direction of travel.

[Zonther]

9 minutes ago, OhYou_ said:

I would just use relays. you can literally buy a relay hat for a raspi. 
it just drops on and then you should be able to figure out from there how to wire it so that you can enable a set of relays for the desired direction of travel.

I will have to look into it. They look like they cover all the GPIO pins and I would need to figure out how to hook up buttons to tell the Pi to turn either turn on GPIO 14 or GPIO 15 to control the rotation of the motor. 

[OhYou_]

look for some that have the keyword "stackable", they will have full gpio pin passthrough. obvious but take care not to use gpio that is used by the hat board.

[Zonther]

2 hours ago, OhYou_ said:

look for some that have the keyword "stackable", they will have full gpio pin passthrough. obvious but take care not to use gpio that is used by the hat board.

Will do! I think I got it work the way I want by testing first with LED's first.

[Zonther]

So I finally got home and started testing my setup, I figured out that the GPIO doesn't put out enough power to power the gate (base) so I need a GPIO pin to each gate in order to make my circuit to work correctly. Thank you for your help and information you gave everyone!

[Zonther]

3 hours ago, FI Fheonix said:

However, it is important to be aware that this transistor offers a constant DC collector current of 800 mA,

Thank you for the tip! I would be scratching my head on this one because the GPIO pins can't put out enough current to control two transistors at once. So I would need a GPIO pin per transistor.

[AbydosOne]

2 minutes ago, Zonther said:

Thank you for the tip! I would be scratching my head on this one because the GPIO pins can't put out enough current to control two transistors at once. So I would need a GPIO pin per transistor.

Or you could Darlington pair them (i.e. use one transistor to drive the base of one (or more) further transistors).

[Zonther]

So I ended up using two relays. The issue I was getting is that the power going to the motor was reading only 2.5V regardless of the amount of power I try to send it. I tried 3.3v, 5v and 9v and all of them gave 2.5v at the motor. The only thing I could do correctly on this circuit was to get two LED's to turn on when I push the button. 

Thank you for the help everyone! I tried to understand some of the other methods that some people gave but I just didn't seem to understand them to well.