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3V DC Water Pump not starting
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3V DC Water Pump not starting

by IoTAll on Tue Apr 06, 2021 5:45 pm

Hi,

I just bought the Submersible 3V DC Water Pump - Vertical Type (PRODUCT ID: 4547) and I tried to power it directly with the 3.3v pin of a feather board, but the motor doesn't spin.

Before this, I tried to power the motor this way:
motor power.png
motor power.png (8.72 KiB) Viewed 84 times

I use the feather GPIO pin pwm capability and the analogWrite function to control the motor. The 5V being supplied by the TPS61023 module, powered itself via the 3.3v power pin of the feather board.

In both cases I hear a small noise from the motor but it doesnt spin.

Would you know why this is not working? Is it a faulty motor or am I doing something wrong?

Thank you!

IoTAll
 
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Re: 3V DC Water Pump not starting

by blnkjns on Tue Apr 06, 2021 11:40 pm

Where did you get this schematic? It looks weird. If the transistor is on the motor gets 5V, it it is off 0V. The diode is in blocking direction, not sure why.
I would put the motor in place of the diode, and turn to a 3V battery power supply, or use a buck converter to turn 5V into 3V.

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Re: 3V DC Water Pump not starting

by adafruit_support_bill on Wed Apr 07, 2021 5:45 am

The schematic is fine - other than perhaps the 5v. The diode is just the usual snubber. It protects the rest of the circuit from the inductive kickback of the motor.

The 5V being supplied by the TPS61023 module, powered itself via the 3.3v power pin of the feather board.

What is powering your Feather? Regulating down to 3.3v and boosting again to 5v if anything, is probably going to reduce the power available to the motor.

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Re: 3V DC Water Pump not starting

by IoTAll on Wed Apr 07, 2021 8:30 am

Hi!
Thanks for the answers!
Here is a complete picture of my setup, I hope this clarifies:
motor power.png
motor power.png (373.78 KiB) Viewed 66 times


I am powering the feather and complete setup via the Lipo battery.

I actually tried with another motor (exact same shape), bought few years ago from another place, I dont remember where, but I think this one was rated for 6V, and this one works!
I am really not sure what is the issue. I thought those DC motors could run at this kind of voltage too. Am I wrong?

I dont understand what is the issue.

I feel that I am asking the battery voltage to 3.3V buck converter of the feather to do a lot, before converting again the voltage to 5V.
Is this setup ok or should I avoid to power the whole setup through the 3.3V pin of the Feather?
In my setup that helps to do this way as I can shut down the complete setup by disabling only the 3.3V feather buck converter.

Thank you!

IoTAll
 
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Re: 3V DC Water Pump not starting

by adafruit_support_bill on Wed Apr 07, 2021 8:41 am

I thought those DC motors could run at this kind of voltage too

Motors need more than just voltage. Power is volts * amps. Without enough amps, your motor will not run.

Running through the voltage regulator reduces the voltage and limits the available amps.
Running through the voltage booster increases the voltage, but reduces the available amps proportionally. (No such thing as "free power"!)

Try powering your motor directly from the 3.7v LiPo.

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Re: 3V DC Water Pump not starting

by IoTAll on Wed Apr 07, 2021 8:58 am

ok thanks!

Tried to connect the motor directly to the battery and it works.
Actually it worked 5 seconds with one motor and not working anymore....
I used a second one this one works continuously.
Both bought from Adafruit.

Weird with the first one, I am wondering if it fried it..

I checked on the feather schematic and the buck converter used is the AP2112K-3.3 which if I read right can give 250mA at 3.3V.
The motor draws 100mA so I thought I would be good to go with this.
Am I wrong?

Thanks a lot again!!

IoTAll
 
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Re: 3V DC Water Pump not starting

by adafruit_support_bill on Wed Apr 07, 2021 9:09 am

Sounds like a bad pump. Probably something like a misaligned impeller binding on the case. Please contact support@adafruit.com with a link to this thread and request a replacement.

The motor draws 100mA.

Motor current varies considerably with the load. And startup is essentially the same as a stall condition until the rotor starts moving.

The manufacturer does not specify a stall current, But I would expect it is probably at least 500mA. The AP2112K-3.3 can probably handle a brief overload at startup. But motors are noisy and power hungry devices. The noise and current surges can cause fluctuations on the 3.3v bus that may cause problems with your processor. You would be better off taking motor power directly from the BAT pin.

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Re: 3V DC Water Pump not starting

by IoTAll on Wed Apr 07, 2021 9:25 am

Ok very clear thank you very much again for the help and very quick replies!!!
Helps a lot in continuing this project!

IoTAll
 
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Please be positive and constructive with your questions and comments.