Need help with driver for 1W Cree on 10-14V

[Teax]

Hi Folks,

I used this great forum in the pastto gather great info about flashlights.

Now I have a little project where I need more help:

I need to power 10 x 1w Cree LEDs by an ATV alternator, so they will see fluctuating voltage in the range of 11-14V or so.

The problem is that this is a kids ATV and per Yamaha does not have any extra power from the alternator. So putting on some 100W lights wont work.

Thus I opted for the 10 1W LEDs which will only draw, well, 1A and should be pretty bright (They will serve more as a DRL than nightstalker light).

I ordered Cree's and reflectors of ebay but now realise that those LEDs need a little more than a little resistor in line. outch!


I looked on ebay and found cheap drivers that drive 3-5 LEDs on an input voltage of 9-20V or so BUT both sellers say that they will not work for my application.


Now I need help to find a rather economic way to drive those 10 LEDs ... I dont want buck rehulators as they will just burn off power I dont have.

So it should be a switching regulator. Do it yourself is possible but I cant make circuitboards.



Ideally I would like to buy a few drivers for abou $40 total or so. Am I crazy?

Please help me with finding drivers that work for me

cheers

Teax

 

[mds82]

I have always had good luck with the LED Dynamics Buckpuck. You could get 3 3023-d-n-1000 from LEDsupply.com.
On each of those drivers you can run 3 led's in series, and shouldnt have a problem with them at all.
you will only have 9 LED's when your done, but it'll work out well. Those drivers have a large range of inputs, up to 32v for spikes

lastly, if you notice the voltage changes ( aka the led's dim or flicker sometimes) you can always add a capacitor in line with each driver to make up for drops in power.

 

[Teax]

are those buck regulators? If so they wil burn off large amounts of power that I dont have

 

[Teax]

I looked at the bickpucks and other drivers and I understand that you have to run the correct voltage into those things, i.e. 4*3.7V if you run 4 LEDs and the circuit will keep the current where it needs to be to power the LED.

But that wouldnt work if the input voltage comes from an alternator which changes from 11-14 or so.

Is this correct? Or will the regulators adjust voltage and amperage?

 

[LukeA]

Buckpucks are upwards of 90% efficient in some applications.

Buckpucks adjust. You can put any number of LEDs from a buckpuck as long as the total forward voltage is less than 1v less than the voltage off of the alternator.

 

[Teax]

Buckpucks are upwards of 90% efficient in some applications.

Buckpucks adjust. You can put any number of LEDs from a buckpuck as long as the total forward voltage is less than 1v less than the voltage off of the alternator.

Thanks! That seems like a nobrainer devcice! Connect 2-3 LEDs to one and its fire and forget ,

 

[Mr_Light]

A 1000mA 3021 Buckpuck should be able to drive 3 parallel strings of 3 one watt luxeons from 12 Volts or above.

 

[TorchBoy]

:welcome: Teax.

I dont want buck rehulators as they will just burn off power I dont have.

So it should be a switching regulator.

are those buck regulators? If so they wil burn off large amounts of power that I dont have

Buck drivers are switching regulators. I think you're getting confused with linear regulators, which burn off excess voltage as heat. A buck regulator uses only as much power as it needs, which is dependent on its efficiency (edit - and its output, of course).

Some ideas...

Buck: http://www.videofoundry.co.nz/ianma...tock&type=buck&v_in_min=10&v_in_max=14&leds=3
($6.97 for four suitable drivers is probably the best deal for individual drivers you'll find. The set resistor will need changing. Or get just one 1 A driver and use balancing resistors for three parallel strings of 3 series LEDs.)

Boost: http://www.videofoundry.co.nz/ianma...ck=instock&type=boost&v_in_min=10&v_in_max=14

lastly, if you notice the voltage changes ( aka the led's dim or flicker sometimes) you can always add a capacitor in line with each driver to make up for drops in power.

Adding a capacitor in parallel with the driver (input or output) might be good, but in series would almost certainly not be.

 

[Teax]

Thanks Torchboy

I looked at the first from the list:

http://www.sureelectronics.net/goods.php?id=343

It looks exactly like one I wanted to buy on ebay but the seller said it needs a constant supply voltagebuil.

Do all regulators with a input voltage range alow fluctuating input voltages and then output the 3.7 v the LED needs? Or do only some do that?

How do I recognise the ones that do?

I built powersources on things like lm7805 before and for them it doesnt matter if the input voltage changes, the output is always constant.

Is that generally the same with LED drivers?

Cheers
Teax

 

[TorchBoy]

It looks exactly like one I wanted to buy on ebay but the seller said it needs a constant supply voltagebuil.

A constant supply what? It seems a little strange to require a constant voltage regulator to drive a constant current regulator, which should have some leeway in input voltage.

Do all regulators with a input voltage range alow fluctuating input voltages and then output the 3.7 v the LED needs? Or do only some do that?

How do I recognise the ones that do?
...
Is that generally the same with LED drivers?

Basically, yes. Many LED drivers (especially cheap boost drivers) do not have a constant output; their output current normally varies according to input voltage. For constant current drivers you may find regulation isn't good near the bottom end of the input range because of LED Vf and the headroom the driver needs to stay in regulation (normally 0.5-1.0 V above the LED Vf). Just because a buck driver will work down to 3.6 V doesn't mean it will stay in regulation for any particular LED (like one wanting 3.7 V).

But generally any driver that uses the AX2002 or PT4115 driver chips should be good for a 12 V car or quad bike use. Both are more efficient when running 3 LEDs at 12 V than just 1 LED at 12 V.

 

[Teax]

Also my ideas of a voltage regulator is that it takes any voltage above its output voltage and regulates it to a constant voltage that is desired...

But who knows, maybe if the amps are fixed for LEDs maybe that doesnt work .. I am really lost.

Here is what people told me:

item:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250604928582&ssPageName=ADME:X:RTQ:US:1123



Teax:
[FONT='PrimaSans BT,Verdana,sans-serif']Hi There,
would this driver be suited to operate 1W Cree LEDs off automotive voltage that fluctuates 11-14V?

Seller:

[/FONT][FONT='PrimaSans BT,Verdana,sans-serif']Thanks a lot for your letter.
Yes, this driver could power 1W green LED.
Total num of load= Input voltage /4, for example:
Qty
1 White LED:minimum input volatge @ 280mA 9v;
2 White LEDs In Series:minimum input volatge @ 280mA 12v
3 White LEDs In Series:minimum input volatge @ 280mA 17v
4 White LEDs In Series:minimum input volatge @ 280mA 21v
Feel free to contact us if you have any questions.
Best wishes



and:

item:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=330414323735&ssPageName=ADME:X:RTQ:US:1123

Seller:

[/FONT][FONT='PrimaSans BT,Verdana,sans-serif']Dear,it can not.
thanks.[/FONT]

 

[LukeA]

6v is a lot of overhead for a driver. That one is less than 50% by those numbers.

You can either buy those eBay drivers now AND buckpucks later when the eBay drivers fail or just buy buckpucks now and be done.

 

[Teax]

6v is a lot of overhead for a driver. That one is less than 50% by those numbers.

You can either buy those eBay drivers now AND buckpucks later when the eBay drivers fail or just buy buckpucks now and be done.

Dont get me wrong. I didnt want the ebay drivers, but wanted to understand how all that works. The ebay drivers should work in my opinion.

Anyways, I called the people who make buckpucks and they answered all my questions (I recommend the place, great support).

I want to be able to power 4 lights and 6 lights together, so I will get 2 70 mAh buckpuck to drive 2x2 LEDs (2 in series and the 2 in series in parallel). They will draw 7V and use 700 mAh together and then another 700 puck to drive 2 x 3 in series ...

Problem solved!

Thanks everybody for the patient help!!! lovecpf

 

[TorchBoy]

Problem solved!

Except that mAh is capacity. :wave:

 

[Teax]

Except that mAh is capacity. :wave:

mA