I'm trying to work out an idea i have. I don't know much about sensors and such, but I will try to explain best I can. I want to setup 10 sensors to detect whether the sensor is covered up or not(i guess dark vs light or close proximity vs not?) and depending on what sensor is uncovered light up specific LEDs. Should I use 1 arduino to monitor sensors and 1 arduino to handle lighting up certain LEDs connected to certain pins? Is it easy/possible to connect 2 arduinos to do this? What sensors should I use? Searching around I've found photosensors, ones that use IR, capacitive proximity sensors(if i remember correctly). what would you suggest?
Connecting 2 Arduinos, or 100, is very easy. Search for wire library / i2c, though for 10 LEDs you could use a 74hc595 thats just as easy to set up, and inexpensive.
For light level monitoring you might use LDR's, or even LEDs can be used the same way.
Perhaps start with 1 to see if it suits your needs. Once you've got that working 10 will be reasonably easy.
thank you for your response. LDR seems like it will suit my needs and pretty low cost.
I'm sorry but I'm not totally sure what to do with 74hc595. I'm very new to using microcontrollers, other pcbs and coding in general haha. sounds like I can hook it up to arduino and get more outputs? control more LEDs? Would that allow me to read 10 sensors and control 10 LEDs?
As far as i can see you do not need any 595 shiftregisters. They are primarily used to expand the number of digital outputs on the Arduino board if you need more than it comes with.
But if you need 10 LDR's hooked up to Arduino you will have to expand the number of analog inputs. Arduino has 6 analog inputs that can do ADC (Analog to Digital Conversion) this is how you would "read" the level of light. You hook up a LDR together with an ordinary resistor as a voltage divider between Arduinos 5V and ground and an analog input. (saerch the forum for LDR and voltage divider to find out exactly how).
To expand the number og analog inputs you would use for instance a 4051 multiplexor IC. Here is an example from the playground on how to do that. Arduino Playground - 4051.
This setup uses 3 digital pins to address the 4051(s) and 1 analog input to read them. This would leave you with 5 original + 8 new (on the 4051) analog ins for sensors and 11 digital pins. Enough to contol your 10 LED's and still have one digital pin for other purposes.
Thank you very much, you're post was very helpful!