shining beam 2500mA driver wiring?

[jez]

Hi Webbstarr,

If you mean the small resistor going to the outside ring then that is a mod to change the modes of the board but doesn't change the output.

 

[Mettee]

I really appreciate all your efforts with this.

Was 2.3A about right for direct drive?

The torch is at work right now and I can't get to it till Sunday but getting this list of things to try is promising.

I soldered the led using both the legs with the wire laying across them as it was easier this way without a third pair of hands. Will that make a difference?

How is the front of the board connected to the back? Could one half of the boards regulators not be connected somehow?

I have found 4 C size NiMH at home of the same make Ansmann so i'll take them to work and try those also.

I'll try different wire too and see what happens. Can't imagine a different make of 24AWG will make much difference but maybe a fresh go at soldering will give better connections?

Mettee did you measure the current through the tailcap?

Thanks Guys

Yeah I did tail cap current and all were up over 2.xxx amps no matter the combo. Even the alks....just not much over 2 I did not direct drive it since your set up is not direct drive.

Sounds like your wire, and the soldering on the P7 are perfectly fine. I would look closely at the board more and its connections. Even the smallest dab of solder in a place it should not be will throw things off.

And the 4th cell test as well...didnt want to forget that.

drew

 

[jez]

Righty-o

With the driver back in place and 3d NiMH the amps are 1.7 so up from before a little, whether that is down to better soldering or the fact the batts have had a recharge through them I don't know.

Threw a 4th d cell on top and bang 2.8A which is good as I know the driver is working fine.

Should this driver work with 3 cells? If it does then perhaps my cells are not up to it.

I have 4 c cells at home so i guess i'll be modding for that now.

Annoying as i'd paid out for the D's and now can't use them unless at reduced power - mmm.

Might put some more cycles through the batts and see if they come up more as they are pretty much new.

 

[TorchBoy]

Should this driver work with 3 cells? If it does then perhaps my cells are not up to it.

I have 4 c cells at home so i guess i'll be modding for that now.

Annoying as i'd paid out for the D's and now can't use them unless at reduced power - mmm.

Didn't we figure out that it almost certainly needed that extra cell for the voltage? And didn't your test confirm our suspicions?

Reduced power will give you longer runtime. Always a bright side, it's just that in this case it's a dimmer side for longer.

 

[uk_caver]

For what it's worth, I got a couple of low Vf P7s (H bin) for a little photo flood light, and even with them, I'm pretty much on the borderline between 3 and 4 cells for full power.

Using 7xAMC7135s and running from 4xEneloop AAs, I get ~2.4A, and that current matches up with a measured initial 3.21V across an LED, dropping fairly quickly to ~3.13V as things warm up.

If I try running from 3 Eneloops, I get a measured ~1.55A with a meter in circuit, and ~1.65A if I stick two meters in parallel to drop the resistance. I guess I'd be getting ~1.75A with no meter present.
I do have quite a few contacts adding resistance in that setup, since that is running from 3xEneloops in a battery holder, with a lead running from a PP3 clip on the holder to another connector which then plugs into the light.

If I run from 3xNiMH 18650-ish cells, tagged and soldered, and with just one connector between them and the light, on a part-used battery pack maybe ~20% used, last charged a few weeks ago, I get 2.2A, and without the meter I'd probably be getting the full 2.4A, but only by a pretty slender margin.

 

[ti-force]

Righty-o

With the driver back in place and 3d NiMH the amps are 1.7 so up from before a little, whether that is down to better soldering or the fact the batts have had a recharge through them I don't know.

Threw a 4th d cell on top and bang 2.8A which is good as I know the driver is working fine.

Should this driver work with 3 cells? If it does then perhaps my cells are not up to it.

I have 4 c cells at home so i guess i'll be modding for that now.

Annoying as i'd paid out for the D's and now can't use them unless at reduced power - mmm.

Might put some more cycles through the batts and see if they come up more as they are pretty much new.

Well, at least you've learned about emitter vf right? Measure voltage at the emitter to find out what the vf of your emitter is. Just put the positive lead on the positive side of the emitter and the negative lead on the negative side, then turn the light on. Like TorchBoy said, we already though it was too little input voltage, and that the 3 cells you're using don't supply enough voltage, so measure the vf of your emitter, and that should show you why you need the 4th cell :thumbsup:. Oh yeah, don't look directly at the emitter or you will see dots for a while .

 

[uk_caver]

Oh yeah, don't look directly at the emitter or you will see dots for a while.

I find sunglasses are very useful when doing LED work at decent drive levels.

 

[ti-force]

I find sunglasses are very useful when doing LED work at decent drive levels.

Great suggestion, thanks:thumbsup:

 

[TorchBoy]

Oh yeah, don't look directly at the emitter or you will see dots for a while .

Managed to do that just after wiring up my first Cree XP-G.

 

[jez]

Vf over LED is 3.35v.

I read somewhere that you need 0.6v higher than Vf to run the driver so i'd need at least 4v then?
Did I understand that right?


You would happen to have a link to the 4c conversion as I've lost that too!

 

[uk_caver]

Vf over LED is 3.35v.

What current is that measured at?
(That might be hard to say in a 3-cell setup, unless you're simultaneously measuring the current, given how an ammeter could affect the current being drawn.)

I read somewhere that you need 0.6v higher than Vf to run the driver so I'd need at least 4v then?
Did I understand that right?

The AMC7135 driver chips only specify a typical drop of 0.12V at max current (350mA/chip).
The 0.6V figure might have been making allowances for other losses or changing battery voltages, or referring to a different driver,

 

[jez]

Sorry, I got the same Vf for 3 cells at 1.9A and 4 cells at 2.8A

Took the Voltage across LED then did tailcap current at same setting. Haven't got two meters to do at the same time.

Should they be different?

 

[uk_caver]

They might be expected to be different by about 0.1V

However, one confounding factor can be the heat issue - at the higher current, the LED will end up warmer, which will lower the Vf a little.

 

[Mettee]

Righty-o

With the driver back in place and 3d NiMH the amps are 1.7 so up from before a little, whether that is down to better soldering or the fact the batts have had a recharge through them I don't know.

Threw a 4th d cell on top and bang 2.8A which is good as I know the driver is working fine.

Should this driver work with 3 cells? If it does then perhaps my cells are not up to it.

I have 4 c cells at home so i guess i'll be modding for that now.

Annoying as i'd paid out for the D's and now can't use them unless at reduced power - mmm.

Might put some more cycles through the batts and see if they come up more as they are pretty much new.

For sure the addition of the 4th battery shows the board is fine, and in fact they are up to the task you just need that 4th cell to give it that little push to the happy zone.

That is good news at least...you made some progress.

And yes I think you need a little more than 4v...think of it as if you were running a single Lion cell. They usually start at about 4.2 off the charger.

 

[TorchBoy]

The AMC7135 driver chips only specify a typical drop of 0.12V at max current (350mA/chip).
The 0.6V figure might have been making allowances for other losses or changing battery voltages, or referring to a different driver,

Or possibly got confused with the ~0.6 V drop across the polarity protection diode.

 

[jez]

Me again ,

I'm sure your all fed up with this by now but i've come across something else.

With 4 c cells powering I get 2.8A tailcap current for about 15secs then it rapidly drops all the way down to about 0.7A

The same happens with 4 d cells.

However, with 3 d cells powering I'm getting 2.1A now but it holds steady.

Am I suffering from bad heatsinking i.e too much adhesive on the led?

Thanks

Jez.

 

[Justin Case]

It sounds like 6 out of your 8 AMC chips have hit their thermal limit and the built-in thermal protection kicked in and shut down those chips.

Have you tried eliminating sources of parasitic resistance so that you can run with 3xD NiMH in regulation?

 

[jez]

Hi Justin,

I've done the tailcap spring fix to reduce the resistance there.

I'll look at the switch too.

I could always try 22gauge instead of 24 as well.

 

[TorchBoy]

Have you tried eliminating sources of parasitic resistance so that you can run with 3xD NiMH in regulation?

I dare say that'll only get it to run in regulation for a short time when the 3 cells are freshly charged. Because four flat NiMHs will give fewer volts than 3 fully charged NiMHs, 4 cells will likely drop out of regulation at some point too. How much current does it provide when the 3 or 4 batteries are half or almost completely flat? Is either OK?

Justin is probably right about the thermal limiting, but I didn't get that in my headlamp. Can you cool them easily?

 

[Mettee]

I have run tons and tons of these with no "cooling" at 3.0 amps and they never have problems. I have done 1 sandwich that had a problem and I was never able to see that one again after I sent it off.

you would also think that with 3 SST-50s they would hit a thermal cut off before this light would....especially at over 4 amps.