Simple question

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techguy101010

New Member

• Sep 11, 2009

• #1

Hi,
I'm trying to set up a circuit in which 2 buttons trigger the following:
Button 1: Lights LEDs A and B
Button 2: Lights LEDs A and C
I'm running into a problem here because when I press Button 1, LEDs A, B and C all light up. The reasonable explanation for this behavior is that by connecting A to B and A to C, I've effectively connected A to C.
How do I get around this? I know this is a very fundamental thing.
Thanks

 

microtexan

New Member

• Sep 11, 2009

• #2

How about showing us your circuit. Also think about lighting LED B and A with button one and then LED C and LED A with button two. (Think extra diode)

 

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techguy101010

New Member

• Sep 11, 2009

• #3

Thanks for your help.
I'm sorry, I don't understand what you mean in saying think extra diode.
The circuit is like this:

+5V _______________/ B1 ______A, B____ GROUND
+5V _______________/ B2 ______A, C____ GROUND

(Read "A, B" as branch off to both A and B, both of which then go to ground)
Thanks

 

K

KMoffett

Well-Known Member

• Sep 11, 2009

• #4

This is done with "diode OR'ing".

Ken

 

Attachments

• Diode OR'ing.gif

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ddustin

New Member

• Sep 11, 2009

• #5

Now for the real challenge -- Do it without diodes

 

crutschow

Well-Known Member

Most Helpful Member

• Sep 11, 2009

• #6

ddustin said:

Now for the real challenge -- Do it without diodes

Click to expand...

With single pole switches and no other electronics?

 

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techguy101010

New Member

• Sep 11, 2009

• #7

Thanks, I got it working with diodes.
How would you do it with single pole switches

 

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KMoffett

Well-Known Member

• Sep 11, 2009

• #8

OK. Two options. (Buttons were not spec'ed as SPST-NO)

Ken

 

Attachments

• 2Button3LED.gif

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• 2Button3LED2.gif

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KMoffett

Well-Known Member

• Sep 12, 2009

• #9

One more simplification.

Ken

 

Attachments

• 2Button3LED3.gif

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Roff

Well-Known Member

• Sep 12, 2009

• #10

KMoffett said:

One more simplification.

Ken

Click to expand...

Excellent, Ken. An added advantage is that the current in DA remains almost constant if you have both switches closed, instead of nearly doubling as it would in the previous version, which was almost excellent.