Using Trustfire mini Q5 as a reverse light.

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warachito
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Using Trustfire mini Q5 as a reverse light.

im not sure if this is the right place to ask. this is my first post.

well.. this is the idea.
im trying to use the trustfire mini Q5 driver and led, as a reverse light on my car.
I opened the case and find out that the socket of the bulb is very similar to the shape of the driver and led of that lamp.
so I put the led and connected to the pos and neg.. and looked like this

But!… i tested in my house with a 12 volts adapter. and worked ok..
(remember that this light works with a 3,7 volts 1200 miliamp battery..)
but when i decided to install in the car.. the led burnt :/ dont know why.. is 12 volts as the adapter i used.

what do you suggest guys… a friend told me to buy some resistors to have 3.7 volts instead of the 12 volts.
but tomorrow is sunday and i wont find a store.

thanks in advance and sorry for my english

BShanahan14rulz
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Verify the laws in your area regarding this sort of modification.

One thing to keep in mind is that although the car battery nominal voltage is 12V, it is often several volts higher when the car is running. On average, 13.5-14.5V when running.

You could use resistors to drop that voltage down a bit too, but keep in mind how much power the resistors are dissipating, so that they don’t melt holes in your taillight housings. You will probably need those bulky, ceramic, wirewound resistors that can handle higher powers.

You could use a voltage regulator before the driver to ensure that the voltage that the LED/Driver sees always stays at 12V, but again, keep in mind how much power the regulator dissipates, especially if it is a linear voltage regulator and you are using it to drop lots of voltage.

djozz
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I do not know the flashlight but I guess it is supposed to run at li-ions, max 4.2 V. 12V will instantly fry the driver, or the led, or both. The adapter did not burn it because the current is limited, 500mA , or whatever the adapter delivers at maximum, is fine with the led. A car battery at 12V will try to deliver 20+ amps, instant kill! You will need a different driver in this set-up, a buck driver suitable for 12V input, it regulates it down to a suitable led voltage.

ImA4Wheelr
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Nice work.  I need something like that in a couple of my cars. 

You might get away with connecting 4 of those emitters in series so that they split the voltage.  Just have a switch so you can disable them on the street.  You don't want to blind on coming motorists, especially the ones with blue lights that flash.

Fritz t. Cat
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Omitting the driver and using resistors to get the desired current should work fine except for the wasted power and resulting heat. Four leds in series would be more sensitive to the varying voltage.

Flashlight designers should look at lighthouses and pottery.
这些谁设计的手电筒应该看灯塔,以及在陶器。

warachito
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BShanahan14rulz you were rigth.
the voltage goes up to 14 volts when the engine ir turned on.. the first time i didnt know so i fryed the firts led/driver.
like you said, i used some smalls resistors but they become really hot and also the light of the led was very weak.
i went to an autozone and found this

its a voltage regulator for leds. at 25 watts 6 ohms. its something like ceramic dont know, but it doesnt get hot.
i installed inside the housing of the rear lights and i also used the small lens that comes with the lamp, glued on the top to focus the light.

i will take pics at night to show how it looks.
now i ihave whiter and powerful reverse light :bigsmile:

warachito
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Fritz t. Cat wrote:
Omitting the driver and using resistors to get the desired current should work fine except for the wasted power and resulting heat. Four leds in series would be more sensitive to the varying voltage.

yeap. the heat its a problem in this case.
but i found a resistor in autozone that doesnt gets hot.
worked excellent

warachito
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djozz wrote:

I do not know the flashlight but I guess it is supposed to run at li-ions, max 4.2 V. 12V will instantly fry the driver, or the led, or both. The adapter did not burn it because the current is limited, 500mA , or whatever the adapter delivers at maximum, is fine with the led. A car battery at 12V will try to deliver 20+ amps, instant kill! You will need a different driver in this set-up, a buck driver suitable for 12V input, it regulates it down to a suitable led voltage.

as far as i know. the amps dont kills the led, its the voltage.
the adaptor was 1.2 amp at 12 volts.. but the car is 14 volts aprox when the engine is running.
i used the multimeter to check the voltage of the driver when its connected to the adapter, even if i was using 4 volts up to 12 volts the power on the driver was 3.7 volts (like the baterry they use) im afraid that anything above 12 volts will fry the driver. :S

totilde
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warachito wrote:

as far as i know. the amps dont kills the led, its the voltage.


Estás equivocado….

Mooooooo

Fritz t. Cat
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warachito wrote:
Fritz t. Cat wrote:
Omitting the driver and using resistors to get the desired current should work fine except for the wasted power and resulting heat. Four leds in series would be more sensitive to the varying voltage.

yeap. the heat its a problem in this case.
but i found a resistor in autozone that doesnt gets hot.
worked excellent

All resistors get hot. Some dissipate and withstand heat better than others.

Flashlight designers should look at lighthouses and pottery.
这些谁设计的手电筒应该看灯塔,以及在陶器。

hank
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andyroo54
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Your little power pack wouldn’t supply many amps, so it can’t draw too much current. But your car is usually about 13-14v when running, with TONS of amps available, so it will instantly fry the LED..

I would get something like this and mount it under the rear bumper bar:

http://www.ebay.com.au/itm/30W-3-x-10W-spot-led-lightbar-with-mounts-mod...

I mounted one (I think about 70 watts) in the back of my ute, mine is a work light/reverse light:

http://i.imgur.com/gpzS3Yp.png

http://i.imgur.com/O3e7R6F.png

http://i.imgur.com/BuuKZHs.png