Pump not working

Hi.!

I am making a fire extinguishing robot. Everything else is working just fine except the water pump. The logic pin to which the pump is connected is giving out a voltage of 5V in the presence of fire as expected (which indicates that the logic is correct) when checked with a multimeter. However, on connecting the pump, this voltage goes down to a few millivolts (not sufficient to run the pump).

Also, on connecting the pump directly to VCC (which is also 5V, and cannot be programmed of course), it works (which means that the pump is not damaged either).

So, my issue is why is the pump responding to VCC but not to the logic pin, even though the output voltage in both the cases is 5V.

Please help.

The logic pins can deliver no more than 40mA which is highly unlikely to be able to power your pump.

You will need a mosfet or a relay that the arduino can drive, switching power from an adequate power supply to drive the pump.

Ok, then how much current is delivered by Vcc pin

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html .

Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?

Thanks.. Tom... :)

animesh29july:
Ok, then how much current is delivered by Vcc pin

do not expect to get ANY power from the micro controller, ZIP, NADA, NOTHING.
you take power to your pump
from the pump to a relay, or FET or transistors…
from the relay to ground.
that completes on circuit.
You use the power source to feed the power of the relay board, not power from the Arduino
that is a second circuit
You use a TTL line, a low current signal, to tell the relay/FET/Transistor, to turn off and on.
that is the third circuit.
That might mean 3 separate power supplies.

animesh29july: Ok, then how much current is delivered by Vcc pin

None.

The "Vcc pin" - the "5V" pin on an Arduino - is the pin you use to connect your regulated 5 V power supply to the board.

I suspect that you are presently powering the board from the USB interface which may provide a little more than 500 mA, and can then extract some power from the 5 V pin but this will be limited - on a UNO - by the protective polyfuse and if you were to drive a little motor from it, would probably shut (the whole board) down after a short time.

So you need to specify what your motor is - generally a Web link to it - and what you intend to use as a 5 V power supply for a start.