strange behavior when 2 or more motors are connected

Other Hardware Motors, Mechanics, Power and CNC
1

Hello,

I have build up a simple circuit with HD44780(LCD), L293B and 4x this motors:http://www.robotshop.com/world/dfrobot-6v-180-rpm-micro-dc-geared-motor-with-back-shaft.html, powered at 5V.
With a only 1 motor connected it works great, but when I connect 2 or more motors everything go mad (whole circuit starts reset itself, LCD print strange marks and words, motors works how they want to).
A current draw looks fine (250mA per 1 motor); L293B is powered externally and there should be no short circuit.
I tried to add 100nF capacitor between Vcc1 and GND (internal logic) and 1000uF between Vcc2 and GND (motor supply). Maybe a very little progress here, but still it not working.
Does anybody know, what should be wrong with it, please?

Thanks.

2

nevar91:
Hello,

I have build up a simple circuit with HD44780(LCD), L293B and 4x this motors:http://www.robotshop.com/world/dfrobot-6v-180-rpm-micro-dc-geared-motor-with-back-shaft.html, powered at 5V.
With a only 1 motor connected it works great, but when I connect 2 or more motors everything go mad (whole circuit starts reset itself, LCD print strange marks and words, motors works how they want to).
A current draw looks fine (250mA per 1 motor); L293B is powered externally and there should be no short circuit.
I tried to add 100nF capacitor between Vcc1 and GND (internal logic) and 1000uF between Vcc2 and GND (motor supply). Maybe a very little progress here, but still it not working.
Does anybody know, what should be wrong with it, please?

Thanks.

As always - schematic and code for us...

Also - what happens when you just have the LCD connected (nothing else)? What about just a motor, then two, then three, etc?

Also - L293B... hmm - one version of the L293 has back-emf diodes built-in for the motors, while a different version doesn't (you have to add them externally); maybe that's the issue?

Also - you mention the L293 is powered externally - by what? What are the specs of this power source (and did you connect the grounds together to the Arduino)?

3

Also - what happens when you just have the LCD connected (nothing else)? What about just a motor, then two, then three, etc?

Same problems...

Also - L293B... hmm - one version of the L293 has back-emf diodes built-in for the motors, while a different version doesn't (you have to add them externally); maybe that's the issue?

I tried both L293B and L293D versions...

Also - you mention the L293 is powered externally - by what? What are the specs of this power source (and did you connect the grounds together to the Arduino)?

It is powered directly from 78S05..

I uploaded schematic to here: ImageShack - Best place for all of your image hosting and image sharing needs. It is a circuit with ATmega644P...
The code is here:

#include <LiquidCrystal.h>

LiquidCrystal lcd(25, 24, 20, 21, 22, 23);

void setup() {

digitalWrite(12, HIGH);
digitalWrite(13, HIGH);

lcd.begin(20, 4);
lcd.setCursor(1, 0);
lcd.print("ROBOTICKE VOZITKO");
lcd.setCursor(0, 2);
lcd.print("SPSE a VOS Pardubice");
lcd.setCursor(0, 3);
lcd.print("Stanislav Jirak-4.B");
delay(2500);
}

void loop() {
digitalWrite(16, HIGH);
digitalWrite(17, LOW);
digitalWrite(18, HIGH);
digitalWrite(19, LOW);
lcd.clear();
lcd.print("go forward");
delay(3000);

digitalWrite(16, LOW);
digitalWrite(17, HIGH);
digitalWrite(18, LOW);
digitalWrite(19, HIGH);
lcd.clear();
lcd.print("go backward");
delay(3000);

}

4

I guess the problem is with capacitors, but I dont know what values to choose. I was also thinking about 100nF for each motor, but I am not sure with it.
Pls, help anybody....

5

It is powered directly from 78S05..

What is supplying the power to the 78S05?

6

I powered it from voltage adapter mostly, but the some problems it do, when its powered from battery.

7

What is the voltage and current rating of the power adapter?
What is the voltage and size of the battery?

I suspect they are not providing enough power to run 2 or more motors and the arduino is resetting or otherwise being unstable.