12V DC Water pumps run once and stop with L293D

Hi. I am new to here and come from Korea.

Me and my friend are on school project which is called Color Mixer, making a specific color using acrylic paints by the converted RGB data from Android phone through bluetooth.

So we need 5 motor pumps for CMYKW colors. we just got new pump and tested it. it works very well alone. However when i connect two pumps to my motor driver they just rotate once and stop working. I think its kinda voltage or current problem.. since when i connect only one pump and run the program it is working but as soon as connect another one, they just stop.

Here are my code and names of my pumps and driver.

int motor2_dir1 = 8;
int motor2_dir2 = 7;
int motor2_pwm  = 10;

int motor4_dir1 = 3;
int motor4_dir2 = 2;
int motor4_pwm  = 6;

void setup()

void loop()
    analogWrite(motor2_pwm, 255);
    analogWrite(motor4_pwm, 255);

Motor Driver : http://www.waveshare.com/wiki/Motor_Control_Shield
Water Pump : Peristaltic Liquid Pump with Silicone Tubing - 12V DC Power : ID 1150 : $24.95 : Adafruit Industries, Unique & fun DIY electronics and kits

and just in case i recoreded my pumps : - YouTube
its hard to recognize tho. when i press the reset button it works but soon stops.

Thanks for helping in advance. and sorry for my bad english :slight_smile:

I can't see in your video where the 12V for the motor comes from? (edit: by which I mean, how does it get to the shield? Where is the 12V supply?)

Hi. i connected 12v adaptor to the shield. i also tried to connect it to Arduino Mega and put the voltage adjust switch on the shield to Vin but the result was the same.

What is the stall current for the pump motor?
It is probably far too high for the ancient L293D chip.

Hi! Thanks for reply.

My motor pump uses 200~300mA , as datasheet.

Is it too high? Then..If i want to use 5 motor pumps then what should i do for using high currents?

You need to know the stall current of the pump motor, not the running current.

You will need a modern motor driver for 5 pumps. Pololu has a great selection.

You need to know the stall current of the pump motor

And you can find that by measuring the resistance R across the motor's terminals, then Istall = V/R

Thank you so much guys! now i understand what stall current is and how to measure it.

now i am looking for the driver suited with my project. you recommended Polulu driver but i couldnt find driver for 5 12v dc motors. can you help me a little more? Thanks!

Use more than one motor driver.