Ah ok that makes more sense. Since I have two pairs of sensors, what would be the most effective way to power them? I figure I'll need at least two power supplies, one for the transmitter and one for the receiver end of the sensors
Also I am planning on using a pair of NRF24L01 transcievers, one to connect to the sensors and one to connect to the arduino. So one of the NRF24L01 will have to be powered (preferrably by the sensors power supply) as well. This also means directly connecting the arduino to either of the IR sensors is not an option.
Is there anyway to consolidate the seperate power requirements with limited experience and something I can put together on a breadboard? Without needing 5 seperate power supplies (4 for the sensors and one for one of the NRF24L01 pair)? I guess I could settle for having each of the emitter/receiver pairs powered in parallel since they use the same voltage and a seperate power supply for the NRF24L01, for a total of 3 power supplies (I cant run a cable between emitter/receiver).
I figure I can either use two disposable 6V batteries, a solar-rechargable battery of some kind, or a 12v car battery (which I can charge).
Do I need to limit the current to these devices? Or will they automatically draw the correct amount as long as the voltage is correct?
Finally, regarding the messages sent by the NRF24L01, what would be the best way? I need a way of distinguishing which sensor is activated first so that I can determine which way the vehicle is travelling and hence arriving/departing.
The only way I can think of is to have one sensor pair HIGH when crossed, and the other pair LOW when crossed. Then write the output to a byte somehow so one direction would be 0000 0001 (LOW then HIGH) or 0000 0010 (HIGH then LOW). Although I admit I have no idea how to do this and I haven't yet researched the NRF24L01 transcievers. But then the LOW-active sensor would use a disproportional amount of power to the HIGH-active sensor, or is this negligible given that they would be sharing a power supply in parallel?