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Author Topic: Workplace Status Lights(aka Stop Lights)  (Read 699 times)
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I am planning on using my Arduino Uno R3 to act as a controller for a set of LED arrays. The LED arrays are going to show my workplace status in the form of Stop Lights(green means not busy, yellow working, red don't bug me, etc). The controller will be hooked to my pc via serial usb, and will receive updates from a python script. I plan on working on this project in stages.

Stage 1: Prototype the controller board and write the basic communication code.
Stage 2: Enclose the arduino in a project box, with 3 LEDs to show the state. On one side of the box have the pins available LED arrays(ground + 3 control pins).
Stage 3: Build the LED arrays.
Stage 4: Improve the python control script. Make it so it hides in the notification area(windows) and port to Linux & Mac.

I have a firm grasp on what I need to do for Stage 1 of the project. I need some advice though on the other stages.
For stage 2, what would be the best way to wire the box so I can plug in my LED array but still keep it working without(hence the 3 status LEDs)?
For stage 4, any advice on how to make the python script hidden is welcome.

End note: I may be using the wrong term when I am saying LED array. Whats in my mind is each array is a group of the same colored LED wired together, with one end of the group connected to ground and the other connected to the correct control pin.
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I may be using the wrong term when I am saying LED array. Whats in my mind is each array is a group of the same colored LED wired together, with one end of the group connected to ground and the other connected to the correct control pin.

How many LEDs (connected in parallel) in each 'array'?
If more than two, you'll have to drive them with a transistor, as an Arduino pin cannot supply enough current.
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I'm thinking it might be around 20 in each array. That was part of why I posted here as I was not sure what I would have to do for the components. Programming is my skill set, and I hope to branch a bit.
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I'm thinking it might be around 20 in each array.

Standard LEDs draw about 20mA, therefore 20 in parallel will draw around 400mA.
Arduino pins can only supply 40mA, so you will need to control the LEDs with a transistor.
You'll also need a separate power supply for the LEDs.
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Well I was considering adding a nine volt battery to the LED sign to help with the power requirements. Unfortunately I have no experience with circuitry so I'm not sure how to properly include the transistor(s) and battery in with the system. Would I need a transistor for each array(total of 3) or would one do on the ground side of the circuit?
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A 9v battery will last about 10 minutes!
You'll need a power supply of some sort (wall wart?)

You'll need one transistor for each array (3 in total)

See here for some circuit ideas
http://www.pighixxx.com/abc-english-version/
Card 2 is the one you need.
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20 5mm LEDs is a lot of LEDs and would be quite bright if you use modern LEDs; 5 or 9 would seem more appropriate if you're using a frosted lens and can spread the light out a bit. Anywho, you'd assuredly want to use a wall wart to keep your Arduino powered without relying on your USB power, and then the wall wart can also power your LEDs (sourcing power from the Vin pin). A ~12V wall wart would work well so you can put more LEDs in series. LED Wizard will help you figure out the series/parallel wiring and what resistor to use, and Henry already pointed you to the ABC thing for the transistor part.
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