Speed control 3 DC motors

Hi all

I tried to avoid the arduino use for this project, but it didn't worked out. (I'm newbie to this)

I want to controll the speed of a (small) dc motor (voltage: 1.5 - 6V DC / current: 500mA (at 5V) / max current: 2000mA (at 5V).
From very slow (20-30 turns/minute) to very fest (300 turns/minut). I bought this PWM Mosfet controller board:

I connected it to a 9v battery and the DC motor. But when the motor starts to turn, it is turning already quite fast.

Did I do something wrong?

Now I saw this tutorial: How to Control the Speed of a DC Motor with the Arduino - dummies
I haven't made it yet, but I suppose the speed goes from very slow to fast. If so, is there a chance I can connect three of these motors to one Arduino board. And all of them going a different speed.

Thank you for your help!

If you want control at those very low speeds you will probably need geared motors. Most small brushed motors cannot consistently turn that slowly.

If you don't need the motors to turn in both directions then the circuit in your tutorial is close but you will do better with a MOSFET not a bipolar transistor as shown. A quick search for "Arduino MOSFET motor control" will find loads of suitable circuits. If you build 3 of those circuits an Arduino could easily drive 3 motors all at different speeds.

Steve

Hi,

I connected it to a 9v battery and the DC motor.

What sort of 9V battery to power a motor rated at 2A?
What is your motor, please post a link to data/specs?

Does the motor have a gearbox?

Thanks.. Tom.. :slight_smile:

You need a stronger power supply,
more efficient driver board or higher voltage,
possibly geared motors for low rpm,
speed feedback from the motors for a PID controller.

You can start with one motor, adding more later.

Thanks all!

This is the motor: https://www.tinytronics.nl/shop/en/robotics/motors/motor/small-dc-motor-3-6v-type-140

I have a 9 volt: this kind: https://cdn.shopify.com/s/files/1/0105/0974/6233/products/9V_ALKALINE_425x.jpg?v=1613075039

I just need to turn in 1 direction. And it is very important to have it at very very low RPM to a fast RPM.

From what I read:

Thanks!

For practical purposes the Rated load speed is the maximum you should expect to get from that motor. Slower speeds are possible with a control circuit.

So if you want 20 to 300 rpm look for one that says the rated speed is at least 300 but not very much higher.

Steve

That is a geared DC motor indeed.
It is rated for 6.0V. That means at 6V, it rotates with 86 rpm. That is slow.
Because of small differences, the actual rotation speed may vary by 10%.

Panasonic makes good batteries, but you need a good power supply to make your project. At this moment the battery voltage might drop as soon as the motor is turned on.

From very very slow to very fast is not possible with hobby-motors and a mosfet with PWM.

This probably what I need:


With this 'L298N', I can connect and control two motors. Is it possible, with an extra L298N to connect a third (and fourth) geared motor to one Arduino Uno?

Concerning the motor: DC Motor-25 9V/325RPM - robots4all
This one is going fast. Will it turn low RPM's? Would you have an idea of how slow it can go?

jdmo:
This probably what I need:


With this ‘L298N’, I can connect and control two motors. Is it possible, with an extra L298N to connect a third (and fourth) geared motor to one Arduino Uno?

Concerning the motor: DC Motor-25 9V/325RPM - robots4all
This one is going fast. Will it turn low RPM’s? Would you have an idea of how slow it can go?

Going slow or not going at all depends on the load you have on the motor.
Paul

That motor link has no specifications so there's no way to tell if it will work with an L298N which can only handle low currents.

Steve

jdmo, this problem has almost everyone who starts with motors.

You need to find a motor that has the speed, the voltage and strength that you need.
Then you find a motor driver (the module that controls the motor) that is able to deliver the stall current (the maximum current).

Do you have to use a 9V battery. Then you need to find a tiny, small, efficient motor and a efficient motor driver.

I think the geared motor is in this list: https://core-electronics.com.au/makeblock-dc-motor-25-9v-700rpm.html.
It uses 150mA with no load and 2.7A maximum.
The L298N can deliver a current of 2A with a peak of 3A (I think, I did not verify that). That is close, but not good enough. You also need a power supply of 9V and 3A. This is how 9V 3A looks like: https://www.reichelt.nl/nl/nl/compacte-schakelvoeding-30-w-9-v-3-0-a-psac-30u-090l6-p176996.html.

Shall I make a wild guess ? I think the 325 rpm motor can go as low as 10 rpm.
1% is 3 rpm, that might be possible, but I'm not sure.
10% is 30 rpm, that should be easy.

For controlling multiple motors, you should go for h-bridge with Mosfet or FETs i.e. 75N75, L298 is good but its too low powered around 500mA, you mentioned 2000mA … plus it can only control two motors and size is big, FETs are small in size, around 50A max current, you can increase it by adding them in parallel.

Hi,
Do you want to change the motors direction?
If not then you do not need to go to the complexity of a H-Bridge.

Tom… :slight_smile:

Hi all

thanks for the answers. I started off with a small dc motor, a 9v battery and a small speed controller. Close to what I wanted, but not close enough.

Maybe some explanation to the project. It's a music project. I want to attach some sort of small string to the motor, that hits a guitar string. So the result of one of these would be one note going on the same pace, or slower or faster. Adding two or three extra of these would make it far more interesting: making complex rhythm patterns, making drones, phase shifting ... I'm not aiming for pop music, it isn't about melody or chord progressions. It is about minimal music, that concentrates on the very small detail (slow changing rhythm patterns, patterns that shift, ...). Each string will have its own amplification, so I can play with spatialised sound. The build of the instrument will be a lap steel alike, but with only 3 strings, and space in between for the motors.

So, as you see, I'm more a music nerd, then a electronics nerd :slight_smile: I need these electronic solution in order to make this music project work.

It should only turn one direction.

Could this be a solution? 10 Amp 7V-30V Potentiometer & Switch Control DC Motor Driver
Then, of course, I need to buy three of them. One battery would be enough, I suppose?

Is the motor rotation continuously or going forward and backward ?
Can you draw a picture of that string with the guitar strings ? What kind of string is it ? Is it hitting the guitar strings or sliding along the guitar strings (as a fiddle / violin) ?
Should the three motors run at the same pace and with a very specific speed ?
Is it okay if the motor starts slowly, or should the motor start and stop immediately ?
What about the string ? Can it be a rotating disc (as a Hurdy-gurdy).

With big motors, you need a car battery to power it. However, a string has almost no weight, perhaps a very tiny 3V miniature motor will be good enough. Running a normal DC motor with a specific speed is not possible. You might need a motor with a encoder or an other type of motor. Perhaps you don't need a motor at all.

Is the motor rotation continuously or going forward and backward ?

One direction. Different speeds.

Can you draw a picture of that string with the guitar strings ? What kind of string is it ? Is it hitting the guitar strings or sliding along the guitar strings (as a fiddle / violin) ?

I have to investigate what will be the best sounding and the most pratical material to attach to the motor. It will be very light weighted. It is more the hitting of a plectrum sound. Not the bowing of a violin.

Should the three motors run at the same pace and with a very specific speed ?

They need to be controlled seperately.

Is it okay if the motor starts slowly, or should the motor start and stop immediately ?

No, it can go from slow to fast to very fast and back.

What about the string ? Can it be a rotating disc (as a Hurdy-gurdy).

Yes, this is also in the concept. In stead of the string hitting the guitar string, I was planning to make disks to attach to the motor, to achieve a hurdy-gurdy sound.
I learned from previous answers, that I need a geared motor, that can go from slow to fast. I already have a small dc motor, the problem is that is won't turn on low voltages. It won't turn low RPMs.

DC motors require some movement to work. For very slow speed use a stepper motor, provided that its torque is strong enough.

Koepel:
... I think the 325 rpm motor can go as low as 10 rpm.
1% is 3 rpm, that might be possible, but I'm not sure.
10% is 30 rpm, that should be easy.

30RPM would be great.

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