Convoy 5A 12 groups driver current reduction

Flashlight Modding and DIY Parts
1

Hi,
I have recently bought my first Convoy light: Convoy S2+ with Nichia 519A,5A 12groups . I am really satisfied with fabrication quality and LED choice.
I would appreciate longer run times, therefore I am looking how to reduce driver current output by half.
I suppose that the resistor with value R020 is sense resistor - am I right?
What should I do to reduce current to 2,5A? double the value to 40ohms? or reduce it to 10ohms? Is there any formula for relation of max current and resistor value for this particular driver?

2

Modes 7-9 have maximum output of 50% (2.5A). Would that satisfy your needs or are you trying to halve current across all power levels?

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3

Yes, double it.

4

No, the 5A Convoy driver is actually running at 5.7A, so 50% is 2.8A, measured a few weeks ago for another user on here.

5A driver used to max out at 4.8A until components were changed in the process of fixing a mode group reset bug.

5

Not an EE, but if that is a sense resistor, then wouldn’t you halve the resistance in order to lower output?

6

I would like to use lantern mainly with diffuser to light up hunting cabin. So my main intention is to create 5% output providing sufficent light level with 10-12hours runtime.

7

Iout = Vsense/Rsense

Vsense stays the same, the higher Rsense the lower the current.

NewRsense = Iout x Rsense / IoutNew

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8

Thank you. Resistors have been ordered :+1:

9

You need a higher value than R020 since this driver is operating at 5.7A, so doubling it will result in half which is 2.85A

10

My understanding of this circuit is fundamentally wrong. I assumed that was a shunt resistor.

11

Well it is a current sense resistor, or shunt. The voltage across it is compared to a reference so that it’s equal to it.

In this case the reference is Vref = Vsense = Rsense x Iout = 20 x 5 (or whatever current it is in reality as Funtastic stated) = 100mV.

So if you increase Rsense then Iout decreases, since Vref = Vsense and is constant (at 100% mode)

12

Can you share the specs (size) on the resistors and where you’re getting them from?

I may do the same with mine where I’m currently using mode group 8. It would be nice to have 5 levels instead of 4.

13

I’m not positive but I believe the 17mm driver uses a 1206 size resistor; I know the 22mm convoy driver has a 2010 resistor as I just ordered a few resistors to swap on mine. I’d recommend at least 1/2 watt 1% minimum. You can find them on digikey, mouser, etc.

Here’s a link to digikey of 1/2 watt 1% in all the different resistances they have in stock.

14

Thanks for the info crbnfbr. Looks like this would be a good fit at 39 ohms and very reasonably priced (including shipping): RCS120639R0FKEA

BUT, I’ve had numerous issues with these Convoy SST drivers over the years and don’t want to mess anything up. I’ve had flickering issues, 0.1% and 1% essentially being the same, spontaneous programming mode, etc. Luckily the replacement drivers never had an issue.

And I see from my pics that some of the resistors are 10 ohms.

So after additional consideration, now that all 11 of my 50% drivers appear to be stable, I’m just going to be content with 4 levels.

15

Well I messed up with this!!!

Even though I was concern about modding these drivers, I decided to take a chance and mod one to get the extra mode. Why? With 4 modes, there’s a big jump from 3rd to 4th and an extra 1 in-between would be nice.

And if it went well, I’d swap out the resistors on my other quad Nichia E17A flashlights that I have set at 50%.

So I ordered some 1206 1/2 watt 1% SMD resistors on AE. When I replaced the resistor, the flashlight would only turn on in the highest mode and was very dim.

That’s when I realized I got the wrong resistors. I assumed the R020/R010 resistors meant 20 and 10 ohms, but instead they are 0.02 and 0.01 ohms. I ordered 39R0 resistors (39 ohms) and instead I should’ve gotten R039 (0.039 ohms). :frowning_face:

Now I’ll have to wait until the right ones arrive to try again.

16

In case anyone is interested, the correct resistors eventually came and I promptly replaced the sense resistors in all 12 of my E17A flashlights. The first one I replaced I made sure the functions worked as should, which it did, and then onto the next one.

I was planning on doing a couple at a time over weeks, but I got into a groove and replaced them all in 2 days.

For the drivers that were using R010 resistors, I stacked 2 R039 (parallel) resistors to make 0.02 ohms.

The firmware was not impacted with any of them and thankfully it also didn’t change the brightness of the lighted switches.

I’m thrilled to have all 5 modes now! :star_struck:

Here’s a 20mm R010 driver that I replaced with parallel R039s:

IMG_5888
IMG_58881920×1440 211 KB
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IMG_58901920×1440 190 KB

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