High-Power LED Flasher

Thread Starter

turnertj

Joined Nov 4, 2009
78
Hey guys...

It looks like we're going with one white LED and one Green LED. That works the best for our application. But what I was wondering, can the white LED also be used with another BuckPuck to run in a constant on mode? Like a whole other circuit with only the LED in common? I was thinking of something like a 3-way switch so only one of the circuits can be on at once. Would that work?

I have all the parts ordered up, so hopefully I can try it out?

Thanks!

Tj
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
Ahhh...that would probably help! I was referring to Bill's on Post #28.

If I keep the two LEDs for the strobing with the 700mA drivers (it seems the green can only be driven at 700mA, but the white can go higher) can I use another driver with the same white LED to make it have a higher output when used alone?

I guess what I'm asking is this: Can I hook up another driver to the white LED (so it will have two in total) that is only used when using the white LED alone in constant mode? Then toggling to another setting would turn off the "constant" driver and activate the strobe drivers (one on the green and the seocnd on the white LED)?

I'm sure it's not elegant, but I could see how I could do it with it's own power source, i.e. 2 more batteries. But then would I be putting current down the other driver hooked up to the white LED? And if so...what would that do to the "off" driver?

Thanks!

Tj
 

Wendy

Joined Mar 24, 2008
23,415
They pegged me for another weekend, and the boy has a busy weekend (which means I do to), so it will be a little while before I get back here again (and more importantly, draw).

The BuckPuck I suggested will allow you to tweak the current though the LED up. Of course this will affect battery life a bit. A simple push on/push off (or toggle switch) will allow you to turn the white on continously, which is what I assume you're after.
 

SgtWookie

Joined Jul 17, 2007
22,230
Tj,
It depends on the construction method that you will use for the circuit.
DIP packages are very handy for breadboarding, and thru-hole PCB construction.
This one is a DIP package: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ICM7556IPDZ-ND

I suggest getting several of them; if you "break" some of them due to ESD or just wiring errors, it's better to have some spares than having to wait for the next shipment to arrive. Ask why I know this. :rolleyes: ;)

Here is a CMOS 556 timer in a SMT/SMD package: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-1338-1-ND
Not so good for breadboarding, but saves space if you are going to design a PCB and use surface mount components.

Here is another DIP CMOS 556 timer, cheaper than the 1st one: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-1859-5-ND

I received a more convenient list of what they had available by searching for "556 CMOS Timer", and then checked the "In Stock" box.
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
Okay...

I took Bill's circuit that he was kind enough to draw up for me in post #28, and I modified a bit. I'm trying to make a second use option, one with a 3-way switch that just turns the white LED on constant. So in the new picture here S1 would be a 3-way rocker switch or something like it. Will the attached circuit work? I was worried that maybe I would be frying the puckbuck that I highlighted in red.

And please forgive my terrible drawing...I only have powerpoint to work with here!

Tj
 

Attachments

Wendy

Joined Mar 24, 2008
23,415
I wouldn't do that, if I were you. You have two outputs of power devices connected together. They're gonna conflict, and possibly both will lose. Even one smoking is bad enough. (Look ma! Real smoke!)

I was thinking of putting a simple switch across C1. If that point goes to ground the white light will light up continuously, and the green light will go out. Simple solution overall. Remember what I said about tweaking the current on the buck pucks too, you can get more current out of them.
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
Excellent...I knew it wouldn't be that easy! So I don't even need a 3rd buckpuck, huh? That's even better, makes it cheaper and smaller!

Just to make sure I understand, if I hook a switch up such that the lead #6 off of the 7556 goes straight to ground and doesn't go through the capacitor, then the white will be on constant without blinking? I never would have guessed that...you can see how far out of my element I am here!

Thanks!

Tj
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
And looking at it again, that's if I have the green LED on top (in terms of the schematic) and the white LED on the bottom buck puck?
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
I kind of screwed up when ordering the buck puck, and instead got this one:
http://ledsupply.com/03023-d-e-1000p.php

It has a pot attached for diming control, but it uses the "control" lead that the 555 timer needs. I could just cut the pot out and that would be fine, but it would be nice to have it to control the brightness if need be, especially for the white LED in constant ON mode. Can I still hook up the circuit from post 28 with the pot in there?

Thanks,

TJ
 

Wendy

Joined Mar 24, 2008
23,415
I'll have to get back with you. The control was important, but it can be worked around. This means we have to add components to turn the power to the device on/off. You are still using 3 CR123 batteries, so we can use digital logic MOSFETs, there is enough voltage to drive them.
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
Don't worry about it too much. I hink to get the prototype working I'll just strip the pot out. That should be fine, right?
 

SgtWookie

Joined Jul 17, 2007
22,230
Don't worry about it too much. I hink to get the prototype working I'll just strip the pot out. That should be fine, right?
DANGER, DANGER WILL ROBINSON! :eek:
(Quoting the Robot from Lost in Space)

I don't know just what the guts look like in the BuckPuck you ordered, but stripping out the pot seems like a terrifically bad idea, unless you like to see expensive LEDs popping and have Fried BuckPucks for dessert.
 

Wendy

Joined Mar 24, 2008
23,415
Hehe, I missed that part. I'm focusing on how to make it work with an unmodified BuckPuck like he's got.

But if you do tear one up, I'd love to see the innards. :) Don't think it will be useful afterwards, but it won't be the first chunk of electronics to die so we could disect it.
 

SgtWookie

Joined Jul 17, 2007
22,230
Why not just order a couple of the correct BuckPucks? The more parts added, the more there is to break.

You could either return the incorrect parts (there will probably be a restocking fee) or keep them for another high-power LED project - or send one to Bill or myself; we might figure out a way to make 'em cheaper.
 

Thread Starter

turnertj

Joined Nov 4, 2009
78
I was afraid of that! I will just re-order. I don't think you can open up the buck puck at all, it's mounted in a type of plastic with only the wirers sticking out. The pot is an external pot

I was thinking that the ones I mistakenly ordered were no different than the ones Bill suggested, but they have wire leads instead of pins...and then the pot was added across the ref and control line.

Once again my lack of electronics background is biting me.

Thanks for the help guys!

Tj
 
Top