Newb - 1st time 80lm project

[thenewguy]

First I would like to apologize; this is probably a very simple and common question.
I've searched many threads but didn't find my specific config or answers to my questions, but I'm sure it has been answered.
I'm overwhelmed with all of the information I've learned so far.

Parts:
LED : 80Lm , 6500K, IF(mA) 300, VF(V) 2.8 – 3.2 (no brand w/ heatsink)
Battery: single CR123 unprotected rechargeable lithium (no brand)
Charger: for the specific batteries
Push Button on/off switch (no details)

I have the LEDs already, but not the batteries. I know the CR123 comes in 3v and 3.7v. Which should I use? I would like to direct drive the LED off a single CR123 cell (if possible) but I have read about different lights with similar configs using driver boards and booster circuits. Since I am not familiar with designing circuits what do I need specifically to run this configuration safety and without killing my rechargeable batteries immediately?

I plan on building a few lights and giving them to friends, I don't want them exploding or dying immediately, I also don't want them to cost a lot.

Thank you in advance.

-Brandon

 

[greyghost_6]

Well im fairly new to this stuff too but know enough to get by, and since its hard to get help on these forums ill try my best.

Since you are using unprotected batteries I would suggest using a regulator/driver. Unprotected batteries and using direct drive can drain the battery far enough to permanently drain the battery (no more charging). Using a regulator it (should) have an auto cutoff to prevent complete draining.

Now your question about 3.0v and 3.7v.
3.7vs are typically your average rechargeable, the 3.0v are usually "primary" which mean they are non rechargeable. Some drivers require batteries in the 3.6-3.7v and will not use the 3v.

Now some questions for you, since im not sure what exact emitter/led you have it will be hard to suggest a driver. Is 300mAh the max amps it is designed for? That seems low to me but totally possible. Here is a pack of drivers you may need http://www.dealextreme.com/details.dx/sku.4451
Now the volts it needs is 1.5 -3 so your rechargeable 3.7s will not work. If you are able to drive the led harder at 800mAh or so you should be able to get some of these http://www.dealextreme.com/details.dx/sku.3256 3.6-9v.

Well I hope this helps get you in the right direction and HOPEFULLY a pro can build on what I said. But yeah find out what kind of LEDs you have so we can find out for sure what they can be driven at.

 

[thenewguy]

Thanks Grey, I've done some more reading, mainly about protected and non-protected batteries. Since a non-protected RCR123 + regulator/driver costs more should I not just buy a protected RCR123? My housing will be sealed with the battery inside (it can be opened but will be difficult and need to be resealed) I plan to add a jack for recharging the battery. The charger will be suited with the correct voltage and current to my battery selection. This way I am less concerned with my friends swapping the batteries out and causing a dangerous situation, i.e. no external from battery regulator/driver.

As for the LED, the spec I mentioned before is all the info I have. They are plenty bright when testing direct drive with both 3v primaries and 3.7v rechargeable, but I assume I'm damaging them even though they all still work fine. Could I just use a 1/2W resistor to protect the LED? Should my, now protected battery, have a regulator too (If I can find those cheap)? I ask only because I read the actual running voltage of 3.7v is less...

I was hoping a single LED driven by a single cell would be safe and easy. The more I read it is not...

 

[dom]

Hi Newguy
Best to get a driver as they are cheap
Many you can check out hear.
http://candlepowerforums.com/vb/showthread.php?t=188227

Get An RCR123 with protection circuit either from AW (search "AW" will bring up lots of hits) -they are very good batteries.
Or other places like Lighthound,Batterystation,DX or Kaidomain.

They all have chargers as well.

I've never driven LEDs direct drive -but many do, probably to the detriment of the LED

Cheers
Dom

 

[yellow]

it has been some years I did what You do now, when I joined cpf...
It is fun and good to learn but, with my experience now, I think that it makes no sense with "normal" lights because it costs more than a very good ready made light which looks and works better ...
... just to give You something to think over


why use driver:
(except for protection of the led and for multilevel output)
direct drive means very quick reduction of output, while a driver keeps the light constant as long as possible.
con - if one thinks this is a con - regulated light will run for shorter time

easier with picture:

take the left side only, pls.
above is regulated output,
below is how direct drive will work.


why use "protected"
ONE SINGLE discharge below 2.5 V (absolute minimum!!!) and the cell is damaged, with no chance to revive it to starting level.
Discharge even lower - dead cell.
ONE SINGLE USE!!!!
problem with led is: our eyes are not able to realise that the light is that dim already.
Protection is a must!

 

[thenewguy]

Dom,
Are you suggesting a setup using AMC7135 350mA and a protected RCR123 as a complete solution?

That seems to be the only solution fitting my spec of 3.7v source and 300mA LED (well 350mA). What about the voltage needing to be 2.8-3.2v?

I missing something, is a 'driver' the same as a 'regulator'? Or is current regulation a part of a driver

 

[dom]

Hi Newguy
That looks like a good solution for what you want.
They say it will work on 2 X AA, ect.Maybe a little less efficiently than with 3.7V batts.

There are more knowledgeable people than me who use the 7135 drivers that could tell you though.
From the little i've read on them they are very efficient at a certain voltage range.

Yes - a driver is known as a regulator as well -either current or voltage.

Cheers
Dom

 

[dom]

Hi Newguy
Sorry - i had completely lost track of what you initially wanted.
If you are just going to be using normal CR123 batts for giveaway lights perhaps your direct drive solution is fine for the cheapest option.

Any non-flashaholic won't be worried about diminishing lumens as the batt runs down.

I'll look twice before i post next time

Cheers
Dom