No problem. You could answer a question Wookie and I were debating on with the parts you have. Have you figured out how you're going to mount the LEDs yet, they will need heat sinks? If you have you could power the LEDs with it and measure the output current through the LED vs. the input current.

It's been mentioned, but don't look at these LEDs directly, especially close up. They are bright enough to do eye damage.

 

Finally bought a breadboard, so maybe I can answer the debate about the current. I'm still wainting for the timing chips to come in...

I do have one question though, I got the rest of the items at a local electronics store. I didn't know it existed, but it's an awesome place. But, they don't have and don't carry a 0.1uF electolytic capacitor. Can I use a regular ceramic disk one, or does it have to be an electorlytic?

Thanks!

Tj

 

Actually, you're better off using other than electrolytic caps for the 1uF and under values.

Avoid tantalum caps though; they can be troublesome because they have such low impedance. They tend to explode if they get a big transient fed to them.

Metalized poly film caps work well.
Ceramic would be OK, if you can get them in values that large without them being huge.

 

Bill...

I'm breadboarding your circuit from Post #28 (attached here again for easy reference). Does Pin 11 get used from the 7556 chip? You show it just kind of hanging out there...

Thanks!

Tj

 

IT WORKS!!! Well...kind of. I got it all breadboarded up, and then turned it on. It strobes, but the LEDs never fully turn off. Any ideas guys?

In fact, it looks like at first they almost turn all the way off, but then the strobing effect gets less until it looks like they are both on constant...with a little flicker. If I pull one of the LEDs off the circuit (either LED), then it strobes just fine.

Also, if I wanted them to strobe a little faster, do I just have to change the pot to a higher resistance value?

Thanks!

Tj

 

Sounds like a job for... BILL!

If you want them to strobe faster, decrease R3. If it still isn't fast enough, change R1 to 20k.

 

Awesome, thanks. I'll head to the electronics store tomorrow.

Bill...help with the strobing?!

Thanks.

Tj

 

To help Bill out, it would be great if you could take some measurements as to what voltage levels you see on the Cntl inputs when you have just one BuckPuck connected vs when you have two connected.

 

Absolutely. Do you mean mean physically disconnecting the buck puck and not the LED? I was just unplugging the LED and leaving the buckpuck in place for that LED.

And do you mean the control input to the buckpuck relative to ground?

Tj

 

Absolutely. Do you mean mean physically disconnecting the buck puck and not the LED? I was just unplugging the LED and leaving the buckpuck in place for that LED.

That will work. Basically, trying to get a baseline of what works, vs what doesn't work.

And do you mean the control input to the buckpuck relative to ground?

Yes.

 

I may have figured it out. I was jury-rigging it with a 9V, becuase I had some lying around and I don't have a huge pile of CR123s. And the 9Vs were dead...with a fresh one it seems to work...but then it dies FAST!

 

One more thing...

Even with fresh batteries, I'm getting only 400mA out of the lower buck puck to the LED, and only 600mA on the upper buckpuck. When I run the same battery on one of the LEDs with a buck puck hooked up, i.e. constant on (in another circuit) I pull 1A.

Is that right, just circuit losses?

Tj

 

Howdy, just woke up. It will take me a little while to get on line. I think the color of the LEDs will affect current.

I'd get a large battery, or better yet, a bench supply to test this sucker out.

Swap the two pucks out, and see if they act identical.

Slow the flasher down, way down, so you can get some measurements.

I'm about to head off to work, when I get a chance I'll follow up.

 

Thanks. I may have to grab a power supply from work.

Correct me if I'm wrong though. If I'm drawing 1A on a circuit, and my batteries are 1000mAh, then they should last for about an hour, right?

 

I think the run time for the CR123 batteries were posted in a graph way back towards the beginning of the thread.
[eta]
Top of the 4th page:

If you try to run that thing from a 9v "transistor" battery, it'll get sucked flat in no time. 9v transistor batteries are puny in power output. Their mAh rating is based on a constant current discharge over a 20 hour period. Discharging them under a heavy load makes that rating go right out the window.

 

I totally forgot about that graph. It explains it all. I was surprised how fast the 9Vs were drained. They are like 450mAh, so I was expecting at least 10 minutes or so, but not even close! pretty impressive. I'll have to find a bench power supply to play with.

Tj

 

Bill...

I was thinking of trying out the effectiveness of alternating strobe LEDs and a single LED strobe. I know (from experience now) that I can just pull out one LED-or buckpuck from the circuit and have the other flash. But it seems like overkill to use a dual 555 chip to make one flash. I was reading through your posts on the 555 chip and circuits, but I can't quite figure out how to make the circuit work with the buckpuck. That should be pretty easy, right? Do you have a diagram of something like that, or a quick way to alter the one you sent, to use a single 555 chip and a single LED to strobe with the buck puck?

Thanks!

Tj

 

It is up to you, but the difference between a 556 and 555 is pretty small. If you don't use half of it no big deal. I'll draw a single 555 version when I get a chance.

So, did you have a chance to measure LED current and voltage vs input current and voltage yet? My curiosity bump is itching.

 

I'll just use the 556 then and unhook one of the buckpucks.

I did measure the currents, and I'm getting 600mA on one LED from the buck puck, and then 400mA on the other LED. Any idea on why it's so much less on the second buckpuck? They are supposed to be driving the LEDs at 1000mA.

Also, someone got dorked up and I can't find it on my breadboard. The LEDS both stay constant on when I turn on the circuit. When I pull off the second buckpuck then the first LED flashes again. I can't find what is going on though. Any ideas?

Thanks!

Tj

 

Also, what kind of voltage and current should I put in this thing for a bench power source? I found a battery charger in my basement that delivers 15V and 1.2-1.7A. Would that work?