I am doing a project at collage that involves 2 hit sensors an arduino uno and 5 bi colour led clusters (red/geen). The sensors trigger either a red light or a green light on one of the 5 clusters. The led’s that i am using are 2 pin bi colour led but there are 21 in each cluster. The way they are wired up are anode to pin 1 for example and cathode to pin 2 this way i can control the colour with the pin status ether high or low. My problem is that i need to be able to drive all 105 led’s at once and since the arduino can only provide 20mA per pin this is not enough. I have tried Darlington pairs but this only powers my polarity one way. Hope someone can help me with this

Many thanks Joe

 

Hey Joe-

What collEge do you go to?
What year are you in?

 

You might try using L2722 dual power opamps as voltage followers (your I/O pin to the noninverting + input, inverting input wired to the output.) They aren't rail-to-rail, but they can source or sink up to 1A current.

L2722's are made by ST Microelectronics. They have a higher current rating and will go closer to the rail than the industry standard L272 dual power opamp. They're under $1/ea.

You might also consider using MOSFET dual low-side gate drivers.

 

Thanks for that new method i will try it this week. So for each pin i need to use the L2722 dual power opamps to get the power gain i need (2 in total for 1 led cluster). Many thanks for the advice

 

I am at thomasadams colllage in Shropshire and am in year 12

 

colllage

It's mean to pick on spelling though. Sorry

What are you using for hit sensors? I'm curious as to what method you are using for more I/O on an Arduino.

 

Sorry College

I am using 2 piezo knock sensors http://www.arduino.cc/en/Tutorial/Knock
Sorry i am not sure what you mean by I/O on an Arduino.

 

I guess I was wondering if you were controlling each LED in each cluster, or having each cluster one color or the other.

Controlling the individual LEDs would take a lot of Input/Output pins (I/O)

 

Yes I am making all the LEDs in the cluster the same colour either red, green or off. I am actually making a modern pentathlon shooting target (http://www.youtube.com/watch?v=9_c0qLrYnig) just so you know what i am going on about J

 

Sorry i am not sure what you mean by I/O on an Arduino.

Look here under the Functions heading:

http://arduino.cc/en/Reference/HomePage

 

I've done this with a PIC for bullseye handgun competition, but using real bullets.


Voice of "Ready on the Left, Ready on the Right, The Firing Line is Ready, Stand By". Random (2,5) pause, targets turn, shot clock starts.

I have a Hammerli pellet pistol exactly as shown in the vid. AWESOME "BB Guns", Pity they cost over 2 grand. Nice electronic trigger though, so I can see why it was adapted to laser detection.