I want to connect power to a 3V DC motor straight from 3v3 GPIO. Is it safe or will I brick my Pi 3B+ ?
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1Depends on the motor and how you connect it. I wouldn't use 3.3V - 5V is OK– MilliwaysCommented Feb 28, 2020 at 3:57
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Hello @Redlik, Welcome and nice to meet you. Ah, let me see. I think there is 97% chance you will fry the toy sooner, or later, for the following reasons: (1) Murphy's law says "Whatever Rpi will fry, will fry", (2) Doris Day also says "Whatever Rpi Will Fry, Will Fry", (3) JM Keynes also says: "In the long run we [Rpi's] are all dead", / to continue, ...– tlfong01Commented Feb 28, 2020 at 4:07
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(4) Lenz's Law says: "Every motor has a back EMF to fri your Rpi". Every motor has a start and stall current many times than the working current. Eg, if your 3V motor drinks 500mA when running, the start and stop current might be 1.5A, frying the Rpi. Eg, When you try to break/switch off the current of a running 3V motor, the motor's inductive coil refuses to break the current passing through it abruptly, and would try to counter the current change, using whatever back EMF to maintain the current, and often many times than the supply voltage. / to continue, ...– tlfong01Commented Feb 28, 2020 at 4:08
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So, there might be a 10 volt or higher to oppose the current change, this current, running in the opposite direction, shorts the Rpi power and signal circuit, generates heat, which happily fries the electronics stuff, and raises blue or white smoke, so get your smart phone camera ready to selfie the memorable moment of smoke getting into your eyes :)– tlfong01Commented Feb 28, 2020 at 4:09
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In case you would like to look at the back EMF voltage pulse that might fry your Rpi, here is a scope screen capture: "5V Solenoid creates a Back EMF 25V peak to peak": raspberrypi.org/forums/…. Good luck, good health, and God bless your Rpi. Cheers– tlfong01Commented Feb 28, 2020 at 5:56
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1 Answer
In my estimation, there is a good chance that you will "break" your RPi. Connecting GPIO pins to DC motors is not a good idea; you shouldn't do it unless you're OK with breaking your Raspberry Pi.
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Motors are reactive loads. They're likely to fry your Pi. Commented Feb 29, 2020 at 3:50
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It would be helpful to me if you could explain why capacitors are, or appear to be, safe and motors are not. A line or two of comments or a link should get me started. Thanks. Commented Feb 29, 2020 at 12:31
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@BobBrown: I didn't intend my comment to be sharp; hope it wasn't interpreted that way. An accurate explanation requires far more space than available here, but if you have some background perhaps its useful to start with
back EMF. To start nearer the beginning, search the termELI THE ICE MAN; a mnemonic device we learned as freshmen in EE undergrad. L*di/dt is also a key concept. I'll be glad to chat (see link in margin below) if you think it helps.– SeamusCommented Feb 29, 2020 at 22:47 -
Thanks. I didn't take it as sharp. I just want to learn, and I'll follow the info you've given. Commented Mar 1, 2020 at 2:43