# 555 LED "breathing" circuit help

Discussion in 'General Electronics Chat' started by bakayara, Dec 10, 2009.

1. ### bakayara Thread Starter New Member

Dec 9, 2009
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I've been Google-ing for what I'm trying to do and this thread appears really close so I'll try asking here...

I'm capable enough with building circuits but not really with the design...

What I'm trying to do for my son's motorcycle is build a circuit that will fade-on/fade-off the LED accent lighting he already has on his bike when it's parked... The LEDs are in strips of 6 SM LEDs in a silicon tube with appropriate resistors (looks like a SM with 301 on it, 2 per strip) to allow them to be run off a 12v circuit...

There are total of 6 strips that I need to control... Right now they are wired into a little aux "fuse box" under the seat with six 5 amp fuses, one per strip...

It looks like a timer circuit based off a 555 chip is my best bet but I'm unsure of the math to adapt the various circuits presented here to 12v operation and how to calculate values for the delays... Ideally I'd like cycle along the lines of 2-3 seconds of ramp up to full brightness, 2-3 seconds at full, 4-5 seconds dimming to off, 2-3 seconds off & repeat...

Can someone take a bit of pity on a non-mathematical sort and help me out with the values that I'd need? The kiddo always has a bit too much faith in the old man's abilities, but I think that I can fake it if I can get a little direction..

(Re-posted and re-worded from an 'attempted threadjack' )

-=- slp

Last edited: Dec 10, 2009
2. ### rhythmtech New Member

Jan 7, 2009
7
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Try downloading LTspice, there is a 555 in the example files you could play with it to find which values would work best for your setup.

http://www.linear.com/designtools/software/ltspice.jsp

I am usually too lazy to get a 555 circuit made up and I usually just use a microcontroller instead because you can tailor your ramp and fade times by just updating flash memory instead of changing component values. I lean more towards coding anyways, and you can get microcontrollers so cheap -

http://moderndevice.com/RBBB_revB

\$12 for a everything but the comm board to program it which is \$15

3. ### mithunsaha New Member

Dec 10, 2009
3
0
Hi guys,
I am new here. I don't know how to post or how to ask question to u guys??? plzzzzz let me know some idea...

Thankxxxxxx

Jan 7, 2009
7
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5. ### Wendy Moderator

Mar 24, 2008
20,735
2,499
Hey guy, sorry I missed your first post.

I've never built this, but I think it will work.

I'm not sure of your LED setup, this was a guess for a car unit I made.

The good news is it will be extremely energy efficient. The bad news is it really needs a minimum of 12VDC. It could also be pretty noisy RF wise, so if you have a radio around it you may need to add a coil to isolate it. Will it work for your application?

Last edited: Dec 11, 2009
6. ### bakayara Thread Starter New Member

Dec 9, 2009
3
0
Thanks Bill, that looks like what I'm gonna need... Will run it through LTspice and then pick up the stuff for a build whenI get into town on Monday...

Thanx!