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Topic: Multiplex IR LED's? (Read 7 times) previous topic - next topic

Grumpy_Mike

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The top ones are supposed to be LED's and the bottom ones are sensors so that I can have a matrix of LED's lighting up when the sensors detect ir light

In that case scrap that circuit it will not work for LEDs.
Read:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html
For basic information about a matrix.

xXN1pplefaceXx


Quote
The top ones are supposed to be LED's and the bottom ones are sensors so that I can have a matrix of LED's lighting up when the sensors detect ir light

In that case scrap that circuit it will not work for LEDs.
Read:-
http://www.thebox.myzen.co.uk/Workshop/LED_Matrix.html
For basic information about a matrix.

Why wouldnt it? Cant I just rapidly iterate through each of the leds and turn them on

Grumpy_Mike

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Cant I just rapidly iterate through each of the leds and turn them on

Not really the refresh rate and the on / off ratio would be rubbish. With an on off ratio of 64 : 1 the LEDs would be too dim. The 4051 has too much internal resistance to compensate for this by boosting the current and all the current has to come from the arduino pins. So while it would function it would be rubbish.

xXN1pplefaceXx


Quote
Cant I just rapidly iterate through each of the leds and turn them on

Not really the refresh rate and the on / off ratio would be rubbish. With an on off ratio of 64 : 1 the LEDs would be too dim. The 4051 has too much internal resistance to compensate for this by boosting the current and all the current has to come from the arduino pins. So while it would function it would be rubbish.

Ahh I see

So instead of using the 4051 you suggest I use something from the 74LS series or use a shift register?
After reading your article thoroughly it seems the 74LS seems like you choice you suggest, but you also mention shift registers, and since I'm looking to reduce the output pins as much as I can, that looks like a better Idea as your article says I only need 3 pins which is amazing, I have to go to school now but I have one question before I go :P
Do shift registers take inputs or should I just use the 4051 for the inputs since the sensors dont need to refresh as fast as the LED's, or even, should I use a 74LS series incase?

Grumpy_Mike

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Do shift registers take inputs

There are shift registers that output parallel data from a serial input and other types that output serial data from parallel inputs.
But these are digital inputs, for your sensors you need an analogue input so go with the 4051.

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