Sizing Power Supply for DC Motor

[BrknFngrs]

Hoping someone here may have a bit more experience with DC motors than I do. Side project at home has me needing to power a small DC motor to stir some coffee beans, but I’m not sure how exact I need to be on the voltage/amperage for the motor to work and avoid burning it out.

It’s a cheapy motor from Amazon with the following specs:

Rated Voltage: DC 12V
Reduction Ratio: 1:31.6
No-Load Speed: 100rpm
Rated Torque: 4.5kg.cm
Rated Current: 1.1 Amp

I had hoped to just use some kind of old charger I have around the house, cut the plug off and direct wire it to the motor, but most of the chargers I have laying around are lower amperage than the motor spec. Assuming this could cause issues? Any shops in Calgary that might have a good selection of small power supplies for a project like this?

[msommers]

Can you post the motor you bought? A pretty generic AC to 12v DC power supply that's say 2A will work great. They're like $25-30 on Amazon.

[BrknFngrs]

Oh perfect, I was hoping that might be the case. Wasn’t sure how big of a concern it was if the power supply amperage was a bit higher than the 1.1 Amps listed in the motor spec. Assuming it’s better to overpower a bit vs underpower?

It’s this motor here:
https://www.amazon.ca/Greartisan-Ele...072R57C56?th=1

Any idea if some kind of simple inline switch/control might also let me modulate the speed?

[firebane]

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Oh perfect, I was hoping that might be the case. Wasn’t sure how big of a concern it was if the power supply amperage was a bit higher than the 1.1 Amps listed in the motor spec. Assuming it’s better to overpower a bit vs underpower?

It’s this motor here:
https://www.amazon.ca/Greartisan-Ele...072R57C56?th=1

Any idea if some kind of simple inline switch/control might also let me modulate the speed?

You could have a 12v 20a power supply but it won't matter cause the motor will only use 1.1a
Now if you had a 12v 0.5a power supply then the motor won't work or work well at all.

You could try to put a rheostat inline but on a motor that small reducing power is going to make it weak as shit considering it only spins at 100rpm.

[The_Penguin]

You'll want a PWM motor speed controller.
Something like this:
https://www.amazon.ca/Voltage-1-8v-M...hlbWF0aWM&th=1
Maybe something with a slightly higher current. Check the max continuous rating.

[Darell_n]

I’ve used this Amazon one a few times on a blower motor and seat / steering wheel heaters. Works well.

https://a.co/d/2etZKXW

[msommers]

Good call on the controller, didn't think of that.

As Firebane mentioned, the motor is only going to 'pull' as much amperage as it needs. It might be 1.1A but might be a little more when you start it up (sometimes things will spike a bit before they settle). That's where the 2A number came from, I'd be really surprised if it nearly doubled the amperage at anytime.

[BrknFngrs]

Appreciate the insight all - parts ordered and tackling this weekend!

[eblend]

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Appreciate the insight all - parts ordered and tackling this weekend!

Not to beat a dead horse, but as others have mentioned, and many people in general are confused about, is the current. Voltage matters, current on the motor is the max it should draw, so you can give it 12V at 200AMP power supply, and that motor will work just fine, as it will only draw what it needs, but that same power supply could power nearly 200 of those motors from a 200A power supply at the same time. As long as your supply is big enough for the motor requirement, anything over is just overkill.

This same concept goes for people installing a 1200W power supply at home on their PC. 1200W power supply on a PC doesn't mean the PC will be a hungry beast consuming insane amount of energy, but that it could consume an insane amount of energy if you wanted to throw a big load at it like a fancy graphics card. If you put a 1200W power supply into a dinky old Celeron, it will only consume what it needs.

This little triangle is super helpful for people to understand this concept. I know this is an overkill for an explanation, but might be useful for people:



V = Volts
I = Amps
P = Watts

1200W appliance at 120V would draw 10Amps for example.

Your little 1.1A motor at 12V is a 13.2Watt motor. Useful to figure out bunch of electrical things in life

[Flexray]

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Not to beat a dead horse, but as others have mentioned, and many people in general are confused about, is the current. Voltage matters, current on the motor is the max it should draw, so you can give it 12V at 200AMP power supply, and that motor will work just fine, as it will only draw what it needs, but that same power supply could power nearly 200 of those motors from a 200A power supply at the same time. As long as your supply is big enough for the motor requirement, anything over is just overkill.

This same concept goes for people installing a 1200W power supply at home on their PC. 1200W power supply on a PC doesn't mean the PC will be a hungry beast consuming insane amount of energy, but that it could consume an insane amount of energy if you wanted to throw a big load at it like a fancy graphics card. If you put a 1200W power supply into a dinky old Celeron, it will only consume what it needs.

This little triangle is super helpful for people to understand this concept. I know this is an overkill for an explanation, but might be useful for people:



V = Volts
I = Amps
P = Watts

1200W appliance at 120V would draw 10Amps for example.

Your little 1.1A motor at 12V is a 13.2Watt motor. Useful to figure out bunch of electrical things in life

v = L (di/dt)
Or
V = Ea + Ia Ra + IaRse