I've made an installation using Arduino and 6 Sharp IR sensors.
The problem I have is that as the wires to the sensors are so long (15 meters at some points!) the power being received by each sensor is cut down and is not enough.
I therefore want to add some 9v batteries in to the circuit (probably one for two sensors, so three in total).
I'm just a little confused as to where to put in the batteries and how to ground it all.
Any help or links to a SIMPLE explanation would be great,
How much current does that sensor draw? In general the sensors draw very little current so even for 15 meters the voltage drop will not be significant.
Did you measure the voltage at the sensor side using a multimeter? Also, the main problem of this long connection distance is line capacitance and depending on the type of sensor and the frequency it is working under, you may need some sort of compensation circuit to get the sensor to work properly.
Well a data sheet ( http://www.acroname.com/robotics/parts/SharpGP2D12-15.pdf )
shows a maximum current draw of 50ma, so 6 of them might draw 300ma. That’s doable for a Arduino if you aren’t also powering other external components. How are you wiring the sensors to your board? What other components do you have wired to the board?
I therefore want to add some 9v batteries in to the circuit
Don't do this you will destroy both the sensors and the arduino. Both are meant to operate at 5V. It is probably not the power that is the problem but getting the signal back down the long wire.
Are you using analog or digital inputs for your push buttons? I had noticed that if you are reading something on an analog pin, then the voltage can interfere with the adjacent pins, so make sure they are all pulled-up/down appropriately.
This would probably also apply to digital pins if the wires from the sensors run anywhere near the pushbuttons.