Project parts :(I am newbie to electronics
Arduino atmega328, external power source(1amp 12v transformer extended to 3 socket of 12volt outputs and 6 socket of 5volts outputs)
2 stepper motors and 3 servos, all motors and servos are powered from external source.
Now the question is i need to drive 3 servos at a time, but when i connect to external supply of 5v it doesn't move. When i give power from arduino it works. I checked both power readings, arduino gives 5.10v and external gives 4.85 volts. So is this issue because of this readings?
Where should i modify to ensure all parts get enough of power, if its the culprit?
One possible mistake, as has been indicated already, is that you have not got the grounds connected properly.
I assume that you are trying to run the dc servo motors. The difference that you measure between your DC supply and the Arduino output is not significant. You should see your motor running.
What you should do once you have checked the ground connections is to monitor your supply voltage as you connect it to the motor. If it is a supply with the power to drive the motor, the voltage will not reduce by much, if at all, when you connect the motor. If it has no power behind it, the voltage will collapse as you connect the motor.
David
Yes i have connected grounds, but i think its different issue. when i connect only 1 servo it moves, but adding one more to it stops both, both servo just hummers but none of them moves.
Did you follow the advice of datatone to see if the PSU can deliver the required power?
I have connected 3 servo to pins 11,10,9.
How are they connected to the pins? If they are directly connected then you will most likely be overloading the UNO can you post the circuit your using?
Do you have the same problem with the stepper motors?
Seee my earlier message about monitoring your supply voltage as you connect your motors. It sounds like you are using some DC supply that cannot provide the power/current required by the motors. I guess that you will see the open circuit voltage at the 4.8V level that you quoted earlier, then you will see it drop when you connect your first motor. This is because the current flowing in the supply-motor circuit is causing the internal resistance of the power supply (small battery?) to absorb part of the open circuit voltage. When you connect the second motor, more current is required, but the internal resistance of your power supply now limits the power available to the motors to a level that prevents them turning. You will see the voltage drop again.
You need a bigger battery, I think.
I have found many cheap hobby servos while usually using fairly little power will have spikes of massive power usage. This spike will often exceed the maximum current output of the supply causing the voltage to sag. When this happens you may hear the servo humming, but it won't move. Adding multiple servos into the mix will often make things worse.
When testing I usually get around the problem by placing a LARGE capacitor over the output of my power supply so it can make up for the short term spike in demand. Using batteries instead of a supply would also likely solve the issue.
