Some questions about the Shark driver

[Amonra]

i just recieved my shark and have a few questions on how to actually ues it in my application.

I want to run 5 Cree XR-E's in series using a 12V SLA to power them and i want to have a pot to adjust the current between 50 or 100mA and 1A.

I must warn you that i am an electronic idiot so easy step by step instructions are appreciated.

So here are my questions :

when you say jumper J1 u mean solder those two little blobs together ?
how exactly do i add a pot, where should i connect it, and what kind of pot do i need ?
which legs of the pot go where ?
and finally when you say that you pot the board do you mean that you sink it in AA epoxy and stick it to aluminium heatsink ?

Thanks for your help

 

[dat2zip]

i just recieved my shark and have a few questions on how to actually ues it in my application.

I want to run 5 Cree XR-E's in series using a 12V SLA to power them and i want to have a pot to adjust the current between 50 or 100mA and 1A.

I must warn you that i am an electronic idiot so easy step by step instructions are appreciated.

So here are my questions :

1)when you say jumper J1 u mean solder those two little blobs together ?
2) how exactly do i add a pot
3), where should i connect it
4), and what kind of pot do i need ?
5)which legs of the pot go where ?
6)and finally when you say that you pot the board do you mean that you sink it in AA epoxy and stick it to aluminium heatsink ?

Thanks for your help

I numbered your questions to make them easier to answer.

1) short J1 with a wire. I don't think you can bridge across the gap of J1 with just solder. Use a piece of wire to solder across the two pads for J1.

2) To add a pot requires removing the onboard trim pot and soldering the external pot the pads of the trim pot.

3) see 2)

4) Any potentiometer can be used. Your choice of selection. The only criteria is the value of the Potentiometer must be 20K. (I would get an log or volume pot personally vs a linear taper pot)

5) There are three connections on the pot. Solder them to the three connections of the trim pot you removed off the board. There should be the two ends and the wiper.

6) The board *Needs thermal heatsinking* . You need to do something to pull the heat off the board. I would suggest thermally glueing it to the heatsink along with the LEDs, but, that's application dependant. Personally I've blobbed down some AA adhesive and pressed the converter board into it to glue it to the heatsink. Just be careful to not short any of the connections on the backside to the heatsink. You probably don't need to heatsink if your output Power is less than 8W of power. After that I would highly recommend thermally heatsinking the converter board. Assume 80% efficiency. 10W of output (LED) power means 2W on the converter board 80% efficiency, 20% inefficiency = 2W. 80% is just a rule of thumb, but, when driving many LEDs you are effectively driving a lot of Watts and need to take power more seriously than a single LED solution.

-Wayne

 

[Amonra]

Thanks for your reply. just one more question
for the external pot which ends and wiper go where. there are three connections on the trimpot but they are not labelled so where does the first end go ? the second end ? and the wiper ?

Thanks again

 

[IsaacHayes]

Wayne, can you verify I can drive 4 cree's at 700ma with 3.6v input (worse case)?

 

[dat2zip]

Wayne, can you verify I can drive 4 cree's at 700ma with 3.6v input (worse case)?

Your input/output ratio is 3.6V:~14V or ~1:3.9

Simplified calculation is for the current knowing the Vin/Vout ratio and apply the same for the current. 14V@1A equal 3.9 X 1A to get the input Current = 3.9A. That's too much for the Shark. 14V @ 0.7 = 0.7 * 3.9 = 2.73A. That's possibly OK since we did not factor in the efficiency of the converter so input current will be higher than 2.73A by another 15% or so which will go over 3A again, but, not by much. So, 700mA is around the limit for the Shark in this configuration.

It really doesn't matter if you crank it all the way up to 1A. If the converter can't deliver 1A it will deliver the max it can deliver. If that's OK with you, run it to the hilt. If you want constant light for longer duration turn it down a bit.

-Wayne

 

[dat2zip]

I hope 3.6V is the near dead battery state. That's where you need to compute this equation as higher battery voltages will not put as much demand on the Shark.


This is true for any boost configuraration.

For any boost configuration determine your battery chemistry and find what you consider the end of life of the battery. For NiMH and Alkaline that's around 1V/Cell. ~2V for primary Lithium and ~3V for rechargeable li-ion.

Then compute your LED string (assuming they are wired in series).

Compute your input/output voltage ratio.

Use the input/output voltage ratio to determine the input battery current for various output current schenarios and factor in anywhere from 10-30% losses in the converter.

==========================================
Example: 3 Alkaline, 3 Lux3s

Battery near dead state: 3 cells * 1V/Cell = 3V minimum.

Three Lux3s (J bin) 700mA: ~ 3.7V/LED = 3.7V * 3 = 11.1V

Input output ratio 11.1/3V 3.7:1 or 1:3.7 depending on direction.

Efficiency 85% (For this example)

========================================
Substitute into the Power in = Power Out equation.

Power in = Power out =
Vin * Iin = ( Vout * Iout ) / effficiency

Substituting we have 3V * Iin = (11.1V * 0.7A) / 0.85

Solving for Iin we have Iin = 9.14W / 3V = 3.04A.

Once you solve for Iin the only question remaining is whether the converter can suck that much input current (usually the limiting factor).

The IC used in the Shark is rated for 3A and I have recommended to use 2A as a safe number for maximum input current.

-Wayne

 

[IsaacHayes]

Yes good info thanks. Yeah 3xNiMH is the source. They usualy stay higher than 1.2 each, around 1.35 even settled. Thanks for clearing up the current in limits, I was thinking 4amps in was max..

 

[CodeOfLight]

I was thinking of using the shark to mod a replacement for my 18v Ryobi flashlight. I am going to use 5 cree XR-e in series at 700 ma. It sounds like it would work based on some of the earlier replies. I would want to heatsink the board. (Or put a little micro fan inside the casing )

 

[dat2zip]

4 Amps is typical, but, 3A is minimum, 5A max. It's is probably more like 4A, but, it could be as low as 3A and 3A is what you should use worst case. If it's slightly past 3A you are probably still OK. As you move away from Mminimum it's more probably you might get an IC that is closer to min and you mod may not run full power. Then again, for a single mod it's probably not an issue.

If you were to do a production of lights you should only use the mimimum as this would ensure all the lights will meet specifications and you would not have drop out in production due to yield issues.

(I still have my Agilent Hat on and design around worst case numbers, thus, I would always use 3A to ensure 100% yield in production).

-Wayne

 

[IsaacHayes]

ahhh. Got ya!

 

[Amonra]

how do i determine which is the in / out / wiper on the pots ?

 

[modamag]

It's usually the center leg. And in the shark I think it's the one farthest to the right :thinking:

If all else fails, measure with a meter. in to out will yield the maximum resistance.

 

[Amonra]

ok so i just finished a 3 day build using the shark a 12V SLA and 5 XR-E's in series.
I AA'd the shark ( back side ) to a piece of aluminium 10cm long x 3cm wide x 3mm thick which was in turn aa'd to a piece of aluminium hollow section 10cm x 10cm x 20cm long with 3mm thick walls so i guess it has ample heatsinking.
i connected the external pot and wiring as instructed and filpped the switch.
it worked wonderfully and hardly got warm.
so with it turned on i started marking the pot with incremental 100mA positions, when i got to 800mA it went very dim and no matter how many times i turn the pot to and fro it stays very dim. i checked the wiring again and everything was ok. i measured the Vin at the led string and it is reading 12.5V i.e. same as battery.
Therefore the shark is no longer boosting but it is still getting warm, What happened ?
How do i fix it ?

 

[Amonra]

here's how i have it wired and mounted:

I would really appreciate some feed back as i really need this to work soon

Thanks

 

[Amonra]

anyone ?

 

[IsaacHayes]

It didn't short out on the plate when it warmed up and pressed into it? Or did you put on the AA really thick and make sure it didn't sink down into it?

Other than that I have no idea. sorry.

 

[Amonra]

as you cansee in the pic the AA is really thick so i doubt it shorted out, besides if it shorted i guess it would have done it immidiatly

 

[Amonra]

i removed the shark from the HS just to confirm if it had shorted. it did not as it had a 0.5mm thick layer of AA between it and the HS

 

[IsaacHayes]

I only guessed as if it's pressed down it may be isolated but once it heats up it presses into the board from expansion, but yeah you put a ton of AA on there. I dont know what else I'd check other than make sure your POT is still working and connections? :shrug:

 

[Kryosphinx]

First, make sure it's a problem with the shark. See if the LED's work fine and make sure the battery pack is good. Make sure none of the bare sections of the wires are touching anything, make sure all the traces are intact, make sure all the solder is where it's supposed to be.