Running several sensors from one arduino +5v pin - power distribution problems

Hi All,

I'm using an adafruit motor shield on an Arduino Mega which limits me to two +5v pins. I'm trying to run a HC-SR04, Sharp IR sensor and 6 home-made IR bump sensors from one 5v pin.

In order to do this I connected a screw terminal to a piece of perfboard and soldered on two pin strips, one for 5v and one for ground. I then soldered a piece of wire along the pin strips and I'm powering the devices with the pins.

While it seemed that this should have been a circuit in parallel it does not work like this in practice. I get inconsistent readings on the sensors which are solved if I connect one sensor to the 5v and ground pin.

I've obviously made a fundamental error here, probably forgotten something or misunderstood how real life relates to schematics. Can anyone provide a possible solution?

Probably getting motor interference on the sensor pins.
Try powering the motor seperately from the sensors.
Still need to keep all grounds connected.

Thanks for the reply, however this happens whether I have the motors connected or not and whether the sketch only contains one sensor or all of them, I'm pretty convinced it's the way in which I extended the 5v power rail. The motor shield just raises the 5v and ground to pin headers. I am connecting to the same pin with one sensor and it works fine, it's only when I connect via my header strip that the issue occurs

Sounds like perhaps a poor connection then. Or perhaps noise is being picked up on the wires - try adding 1uF and 0.1uF caps from +5 to Gnd on your extender.

would that be 1uf across the pins and .1 across the devices?

That would help. Unless it turns out to be a connection issue.

Check the current requirement of the sensors. Probably, the 5V port on the board is not capable of providing enough current to power your sensors. Try providing an external 5V to the sensors and connect the GND of that supply with that of the Arduino.