Driver only putting out .6v to led

[broncogearhead]

What am I doing wrong? I have 4.2 volts going in (3AAA) and the driver only seems to be putting out 0.6volts.

Using this driver:
http://www.dealextreme.com/details.dx/sku.20330

The led is an SSC P7 with a relatively small reflector (about 33mm).

Wired directly to the 3 AAA's, the light seems as bright as my 2d cell led mag light. I only ran it for a 60 seconds or so because I do not have a good heat sink finalized yet. However it did not get past room temperature.

Is this the driver I should use? I really don't care to have any modes.
Should I use a driver at all? Shouldn't the light be brighter with one?

I would like to use cr123, or maybe a rechargeable cell like a 18650. I only used the 3AAA because that was what came out of the donor light and it was handy.

Any advice or comments?
Thanks.

 

[420light]

I personally do not trust the KD and DX stuff. Add to that that it takes like 2 weeks to get.:shrug:

You may have a bad driver. Did you order 2? Try to wire the spare one in if you did. I would say go ahead mount/heatsink the LED. You know it is working.

What kind of light is this?

Oh and :welcome:

 

[broncogearhead]

Thanks for the reply. I think I am done ordering from them, just cause it takes so long to ship.

I only ordered one. For the price, I should have ordered more, that way I'd have extra in case one was a dud, or in case I screwed something up. Live and learn.

The light was just a cheap 1 watt led flashlight that was about 10 bucks. I had it for a couple of years, and it was never bright. I thought it would be a good cheap starter project. I'll try to get a few pics posted up so you guys can critique it and give me some input for next time.

So what driver should I run if any? I really only want one mode, but would live with one that had a high/low setting if I had too. The body of the light has an i.d. of 1" so that is the size constraint I have.

 

[nein166]

It is a buck driver so I'm surprised it is putting out .6v
If you want it to work give it 8.4v like it says
2 Li-Ions will be fine
2 CR123s will probably work
Be careful with alkalines, make sure the current draw is safe with 5 cells
Don't use 6 cells as thats 9 volts

 

[Justin Case]

What am I doing wrong? I have 4.2 volts going in (3AAA) and the driver only seems to be putting out 0.6volts.

Using this driver:
http://www.dealextreme.com/details.dx/sku.20330

The led is an SSC P7 with a relatively small reflector (about 33mm).

Wired directly to the 3 AAA's, the light seems as bright as my 2d cell led mag light. I only ran it for a 60 seconds or so because I do not have a good heat sink finalized yet. However it did not get past room temperature.

Is this the driver I should use? I really don't care to have any modes.
Should I use a driver at all? Shouldn't the light be brighter with one?

I would like to use cr123, or maybe a rechargeable cell like a 18650. I only used the 3AAA because that was what came out of the donor light and it was handy.

Any advice or comments?
Thanks.

How did you determine that the voltage out was 0.6V? How did you determine that you fed the driver with 4.2V?

What kind of AAA cells did you use? Alkalines? Carbon zinc? These are weak cells with poor discharge current capacity. 3xAAA is around 3.6V under load initially, so you are asking the cells to deliver ~2.8A. The AAAs just can't handle that load. What voltage they actually sag down to and what current they actually deliver, who knows. But it'll probably be weak.

How did you connect the 3xAAAs to the driver? Any possible sources for voltage drop, e.g., skinny wires, long wire runs, poor electrical contacts?

Power the system with a decent power source first, before worrying that the driver might be defective. You have too many possible variables going on to determine if there is any problem at all.

 

[420light]

If you want it to work give it 8.4v like it says

That is a good idea actually. I would slowly go up on the volts though, maybe go to 7 and see what happens. In the process if you fry it then... learn from it.

Experience costs money, How much do you want to learn.

I think I might use that for my sig. LOL

 

[TorchBoy]

Re: Driver only putting out 0.6 V to LED

What am I doing wrong? I have 4.2 volts going in (3AAA) and the driver only seems to be putting out 0.6volts.
...
Wired directly to the 3 AAA's, the light seems as bright as my 2d cell led mag light.

If the LED is making any light at all, it's not putting out only 0.6 V. How did you measure the 0.6 V? Or do you mean you wired the LED directly to the 3x AAA cells?

Six alkaline cells won't give 9 V under load, and the load this driver will demand will be heavy for alkalines - they won't last long. But who still uses alkaline cells for torches? 😗

BTW, I have this driver listed with a "buyer beware" but that's because its output isn't well regulated or the 2.8 A claimed.

Edit: Wow, two new posts while I typed this. What Justin Case said. :thumbsup:

 

[broncogearhead]

Good info guys.
I used my trusted Fluke meter to read voltages.

The three AAA's were in a holder that came with the original light.
not under load, I came up with 4.2 volts.
I never even thought about the voltage dropping when under load.
Really was not planning on using those batteries anyway.

The driver said 8.4 volts max, and the led, said 3.6-3.7 volt input. I guess that is why I thought I could get away testing this thing out the AAA's I had.

I first tested the led directly to the AAA's, it worked.
I then soldered in the driver. It did not light the led.
At that point I checked voltage outta the driver. I came up with 0.6 volts.

I used about a total of 7" of stranded 20ga wire. When this thing in in the light, it will probably be half that length.

So you guys think this thing should work fine with 2 cr123's?
I like the idea of using them cause they are easy to come by and
have a good shelf life.

In case this driver does not work, what one should I look to pick up?
I'm also gonna want a switch in the tail cap, gonna search on here to see what my options are. Might as well order another driver while I am at it.

Thanks for all the tips. Its fun messing with this stuff, even though I really don't know what I'm doing. I will learn along the way though.

 

[Justin Case]

At that point I checked voltage outta the driver. I came up with 0.6 volts.

How did you connect your Fluke to the circuit to arrive at this 0.6V figure?

 

[broncogearhead]

How did you connect your Fluke to the circuit to arrive at this 0.6V figure?

I put the meter on dc volts, and clamped the positive probe to the positive wire off the board intended for the led. Then the neg to neg.

I have limited electrical experience. This is my second attempt to mod a light.
I have been doing some reading on here, and thought I was doing what made sense. Somewhere I missed something.:hahaha:

 

[Justin Case]

Something is wrong since you won't get any output with a forward voltage of 0.6V. The fact that you got output comparable to a 2D Mag means you may have gotten around 40 lumens output. To go that low, you have to be in the 30mA-40mA drive current per core range (and that assumes a D flux bin P7).

Even if the actual estimated lumens output is off -- for example, either 2x higher or half as much -- the bottom line is that the drive current is low and thus the forward voltage is also near the lower limit of around 2.5V to 2.7V typically (see the P7 datasheet and the graph of forward current vs forward voltage).

At 0.6V, the LED isn't even going to light up. Thus, your measurement is suspect.

It is very helpful to show photos of your setup.

I would still suggest using the proper battery configuration to power your 2.8A buck driver, and thus eliminate the complicating variable of 3xAAA being a very iffy power source.

What AAA batteries are you using? No-name, carbon-zinc ("heavy duty")?

 

[broncogearhead]

I guess I should clarify, the only time the led lit was when it was directly running on the battery pack. It was a no go when the driver was added in.

The batterys were run of the mill energizer AAA. Like I posted earlier, that is not what I plan on the finished product running. I just thought it would work well enough to test everything.

I'll have to find the camera and get a couple of pics for a visual.

I'll also try to pick up a couple of cr123 tomorrow. I'll record what comes outta the driver when hooked to those and report back.

Again, thank you all for all the help.

 

[TorchBoy]

Re: Driver only putting out 0.6 V to LED

I put the meter on dc volts, and clamped the positive probe to the positive wire off the board intended for the led. Then the neg to neg.

But was the LED connected at the time? (Not that it makes any difference to the end result.)

 

[Justin Case]

Sounds to me like your AAA Energizers don't have the oomph to power the P7 at all through the driver. When Vbatt < Vf, which no doubt is the case here, your buck driver is going to run in direct drive. There are probably too many parasitic losses in the path for your AAAs to light up the P7.

You need to feed the driver at least Vbatt = Vf + voltage overhead, where the voltage overhead could be 1V-2V. Thus, to ensure that you get 2.8A drive current, you probably want to feed the driver at least 5.5V. 2x123A might not be enough to reach full regulation (hard to say, it might be enough if the voltage overhead is more like 1V). But it still should be enough to light up the P7 with plenty of brightness even with voltage sag under load. 2xLi-ion certainly should get you into full regulation.

 

[broncogearhead]

Re: Driver only putting out 0.6 V to LED

But was the LED connected at the time? (Not that it makes any difference to the end result.)

I don't think it was.

 

[broncogearhead]

Sounds to me like your AAA Energizers don't have the oomph to power the P7 at all through the driver. When Vbatt < Vf, which no doubt is the case here, your buck driver is going to run in direct drive. There are probably too many parasitic losses in the path for your AAAs to light up the P7.

You need to feed the driver at least Vbatt = Vf + voltage overhead, where the voltage overhead could be 1V-2V. Thus, to ensure that you get 2.8A drive current, you probably want to feed the driver at least 5.5V. 2x123A might not be enough to reach full regulation (hard to say, it might be enough if the voltage overhead is more like 1V). But it still should be enough to light up the P7 with plenty of brightness even with voltage sag under load. 2xLi-ion certainly should get you into full regulation.

Things are starting to make more sense now.
I'm pretty sure I can fit 2 cr123 in the light. Anything bigger, it might not be long enough. If i find a longer tube, I could run 3 batterys. Would 3 cr123 be to much? That should be 9 volts, but in actuality, will be a little less because of wire, switch and board resistance right?

I guess I should ask now before I try it, but will direct driving the led to 2 or 3 cr123's make the led go ?

 

[uk_caver]

It's only a thought, but the LED is connected the right way round, isn't it?

Seoul P4s LEDs have a static protection diode that could drop ~0.6V if reverse-connected.
I'm not sure if P7s are the same, but the only ones I have are inside an epoxied-up photography floodlight, so I can't easily check.

 

[bshanahan14rulz]

Re: Driver only putting out 0.6 V to LED

I don't think it was.

Try hooking up the LED and measuring the voltage across it while it is hooked up to the driver while it is on. Some laser drivers crap out and die when you test them with no load (I don't know why, don't ask me). Perhaps some LED drivers are the same way.

 

[Justin Case]

I guess I should ask now before I try it, but will direct driving the led to 2 or 3 cr123's make the led go ?

Yes, you'll your P7 with 3x123A. The P7 might tolerate 2x123A but it's not really a good combination for direct drive either. For direct drive to work well, you need to match the voltage-current characteristics of the LED with the voltage-current characteristics of the power source. Certainly, at ~6V-7V, 3x123A will deliver far too high of a voltage input to the P7. 2x123A may also moderately overdrive the P7, but good heat sinking can allow the LED to tolerate it. It might depend on that initial on-rush when the 2x123A hits the P7 with about 5V before sagging to 4.5V or less.

 

[VegasF6]

Re: Driver only putting out 0.6 V to LED

Try hooking up the LED and measuring the voltage across it while it is hooked up to the driver while it is on. Some laser drivers crap out and die when you test them with no load (I don't know why, don't ask me). Perhaps some LED drivers are the same way.

Yep, some LED drivers are the same way. At least boost drivers for sure, maybe not buck. I was reading a thread sometime ago about how hard it would be to implement open circuit protection for led drivers, I THINK George from taskled was involved in it. Then it was suddenly quite common 🙂