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LED project: Help!

 
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demonwarb
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Joined: 28 Sep 2006
Posts: 1

PostPosted: Thu Sep 28, 2006 6:09 pm    Post subject: LED project: Help! Reply with quote

Well, it's been severl years since electronics class, and I've quite forgotten just about everything. Here's what I want to do:

1. Have an LED increase in brightness over 1-2 seconds (off->max)
2. Trigger another LED (possibly a strobe) to flash once.

I was thinking of using a two-stage 556 timer, (1st stage astable, 2nd stage monostable) for step 1. A simple 555 delay timer would work for step 2 fine.

Now, the problem. I can make the delay timer to trigger the flash, but I can't for the life of me think of a way to make step 1 work. I'd need to change the timing of the oscillator on the fly, I guess. No idea how to make that happen though. Please help!

Thanks
Devin
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Thu Sep 28, 2006 11:33 pm    Post subject: Re: LED project: Help! Reply with quote

demonwarb wrote:
Well, it's been severl years since electronics class, and I've quite forgotten just about everything. Here's what I want to do:

1. Have an LED increase in brightness over 1-2 seconds (off->max)
2. Trigger another LED (possibly a strobe) to flash once.

I was thinking of using a two-stage 556 timer, (1st stage astable, 2nd stage monostable) for step 1. A simple 555 delay timer would work for step 2 fine.

Now, the problem. I can make the delay timer to trigger the flash, but I can't for the life of me think of a way to make step 1 work. I'd need to change the timing of the oscillator on the fly, I guess. No idea how to make that happen though. Please help!

Thanks
Devin


Hi Demonwarb,

What you need to do is set up a simple RC circuit, this link should get you in the right direction:
http://webphysics.davidson.edu/physlet_resources/gustavus_physlets/RCCircuit.html
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