Building a flashing LED - I need help

Kila2000 · Post by **Kila2000** » Mon Sep 26, 2011 4:38 am

Hi guys, hopefully someone can help.
I need to build a flashing LED circuit for my DS9 build. I have a 555 chip as I understand thats the best to use? Thing is, the only calculators I can find online will calulate a flash rate when resistors and capacitor rating are inputted. What I would like to know is what resistors and capacitors I would need to get a 1 second interval flashing light. Also, whats the best way to build up the circuit? I've found tute vids on youtube but they all use a breadboard, I need something permanent.

Any help would be appreciated.

brt · Post by **brt** » Mon Sep 26, 2011 9:13 am

http://wolfstone.halloweenhost.com/Tech ... rCalc.html

The top 555 timer schematic can handle the lights with an on time of just over 50% and an off time a little under. I plugged into the calculator a value of 470 ohms for resistor-1 and 30,000 ohms for R2 with a 47 uFd capacitor and got just about an even split for on and off times for the LEDs of about 1 second each.

http://www.ebay.ca/itm/5-PCS-Bread-Boar ... 2a144df36d

When you are done laying out your work on a breadboard, you can move it over to proto board like this in a size that serves your needs.

USS Atlantis · Post by **USS Atlantis** » Mon Sep 26, 2011 3:42 pm

On a 555 circuit - if you calculate the inverse of the timing you want, then plug a signal diode (1n4148) in parallel with R2 - you invert the timing sequence

Example - you want 1/10th on, 9/10ths off

Calculate for 9/10ths ON - plug in the diode - voila - you now have a 1/10th on-9/10ths off blink

Visual - This Schematic gives this blink rate

Kila2000 · Post by **Kila2000** » Mon Sep 26, 2011 11:11 pm

Thanks for the replies guys.
I perhaps should ad that I'm VERY novice at this sorta thing. I know how to get the right resistors for one or LEDs but anything else is alien to me

I've played around with that calculator a bit but everything I put in gives a similar on time to the off time. What would I need if I wanted a quick on time, like a flash, with around 1 second off time. I'm looking to replicate the nav lights at the tips of the docking pylons on DS9.
Sorry if it appears I'm asking others to do my homework, like I said, I don't really know where to start.

Sloucher · Post by **Sloucher** » Wed Nov 02, 2011 8:29 am

Only just noticed your post Kila.

You could try the second circuit in the link that brt posted (ie the one for duty cycles less than 50%) with values of:
R1 = 2.4K
R2=33K
C1=47uFd

That'll give you 0.078s on and 1.07s off (0.867Hz) if thats close enough to what you want?

en'til Zog · Post by **en'til Zog** » Wed Nov 02, 2011 9:33 pm

Or one self blinking LED in SERIES with several other LEDs. Just make sure that your supply voltage is slightly higher then the sum of the voltage requiements for all the LEDs.

For example:

SELF BLINKING LED - 3 VOLTS

MARKER LEDs - 2 VOLTS EACH

1 SB LED + 3 MARKERS = 3 + 6 = 9 VOLTS TOTAL NEEDED

Try this SERIES stiring outside of the model FIRST, like on an experimenters "bread board".

Kila2000 · Post by **Kila2000** » Thu Nov 03, 2011 3:23 am

Sloucher wrote:Only just noticed your post Kila.

You could try the second circuit in the link that brt posted (ie the one for duty cycles less than 50%) with values of:
R1 = 2.4K
R2=33K
C1=47uFd

That'll give you 0.078s on and 1.07s off (0.867Hz) if thats close enough to what you want?

Hey thanks mate, I was starting to think this had been forgotten. I'll see about getting the bits tomorrow or over the weekend and give it a try.

en'til Zog, I've tried the self blinking option as well but the only ones I can get over here blink way too fast, thats why I've started down the 'make my own' route, but thanks for the input, I really appreciated the help.

Kila2000 · Post by **Kila2000** » Sat Nov 05, 2011 12:17 am

Sloucher wrote:Only just noticed your post Kila.

You could try the second circuit in the link that brt posted (ie the one for duty cycles less than 50%) with values of:
R1 = 2.4K
R2=33K
C1=47uFd

That'll give you 0.078s on and 1.07s off (0.867Hz) if thats close enough to what you want?

Got the bits and pieces yesterday and got this wired up on a breadboard. Burnt out a 555 chip due to a misread of the battery wires but after that was replaced it all goes good now. So once again, thanks for the help on this one. Its one of the bigger hurdles I had for my DS9 build.

Sloucher · Post by **Sloucher** » Sat Nov 05, 2011 9:08 am

Well done Kila!

Glad you only killed one 555!

I've had (still have) more than my fair share of the appearance of "magic smoke!!"

.

Hope all goes well with the rest of your DS9 build.

Kila2000 · Post by **Kila2000** » Sat Nov 05, 2011 3:36 pm

Thanks Sloucher
The only thing I did was to drop resistor 1 down to 470ohms to give a faster on time but without your help I wouldn't have even gotten that far.
I was back to the build last night so with any luck I should have some good photos of my progress later today.

en'til Zog · Post by **en'til Zog** » Mon Nov 07, 2011 9:38 pm

GO! BUILD! WIN!