I'm trying to build an array of IR LEDs to control some model train stuff. I have an arduino programmed to generate the IR codes (pretty normal 38kHz stuff), and a basic circuit that works. However, the signal from the single LED isn't enough to reach everywhere that I need it. Therefore, I want to make a system with multiple LEDs that I can position wherever needed.
Basic hardware design that I'm thinking: The arduino and 5V 2A power supply are in a small enclosure. I'll add a normal RJ45 jack to it and then I can run normal cheap ethernet cables around. Since they've got 8 wires, I'll use one as a common 5V rail and the other 7 to run 7 LEDs from. Cheap splitters (http://www.monoprice.com/products/product.asp?c_id=105&cp_id=10513&cs_id=1051304&p_id=7294&seq=1&format=2) will let me add an LED wherever I need, using a wall mount box (http://www.monoprice.com/products/p...=10517&cs_id=1051705&p_id=7069&seq=1&format=2) with a resistor and LED mounted in the small hole. Each LED will connect to a different one of the 7 remaining wires, so any one of them can plug in anywhere in the system.
To do that, I need to drive 7 parallel LEDs. The LEDs I have are these: LTE5208A (there's a datasheet on that page; I know how much you all love a good datasheet!) Summary: 1.2V, rated for 100ma continuous. Since I'm not running continuous, I was planning for 200ma.
My original plan was to connect the output pin of the arduino to 7 basic transistors (have a bag of pn2222s), with each one then driving one of the 7 lines out to the LEDs. That requires just a 22R resistor at each LED, which some people say is too low and I should switch to a constant current setup. I'm not familiar with that (and barely familiar with the design I've already done), so how would you do it?
Summary: I want to drive 7 1.2V IR LEDs at 200ma each in parallel, controlled by an arduino output pin at 38kHz.
One suggestion was to wire the RJ45 jack so that the LEDs are actually in series - would the fact that there'd be perhaps 30 feet of cat5 wire between LEDs matter? That would also require having all 7 connected all the time, or the series would be broken. It'd also require switching to a 9V power supply or higher. It also has the series resistor on the LEDs being very low again - like a 2.2R if I'm using a 9V supply. Actually, a 12V supply would be simple for what I've already got handy, so that would be 7 in series with a 18R 1W resistor, according to online calculators. Is that ok?
Basic hardware design that I'm thinking: The arduino and 5V 2A power supply are in a small enclosure. I'll add a normal RJ45 jack to it and then I can run normal cheap ethernet cables around. Since they've got 8 wires, I'll use one as a common 5V rail and the other 7 to run 7 LEDs from. Cheap splitters (http://www.monoprice.com/products/product.asp?c_id=105&cp_id=10513&cs_id=1051304&p_id=7294&seq=1&format=2) will let me add an LED wherever I need, using a wall mount box (http://www.monoprice.com/products/p...=10517&cs_id=1051705&p_id=7069&seq=1&format=2) with a resistor and LED mounted in the small hole. Each LED will connect to a different one of the 7 remaining wires, so any one of them can plug in anywhere in the system.
To do that, I need to drive 7 parallel LEDs. The LEDs I have are these: LTE5208A (there's a datasheet on that page; I know how much you all love a good datasheet!) Summary: 1.2V, rated for 100ma continuous. Since I'm not running continuous, I was planning for 200ma.
My original plan was to connect the output pin of the arduino to 7 basic transistors (have a bag of pn2222s), with each one then driving one of the 7 lines out to the LEDs. That requires just a 22R resistor at each LED, which some people say is too low and I should switch to a constant current setup. I'm not familiar with that (and barely familiar with the design I've already done), so how would you do it?
Summary: I want to drive 7 1.2V IR LEDs at 200ma each in parallel, controlled by an arduino output pin at 38kHz.
One suggestion was to wire the RJ45 jack so that the LEDs are actually in series - would the fact that there'd be perhaps 30 feet of cat5 wire between LEDs matter? That would also require having all 7 connected all the time, or the series would be broken. It'd also require switching to a 9V power supply or higher. It also has the series resistor on the LEDs being very low again - like a 2.2R if I'm using a 9V supply. Actually, a 12V supply would be simple for what I've already got handy, so that would be 7 in series with a 18R 1W resistor, according to online calculators. Is that ok?