green led flashlight

gundles123

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Joined
Oct 3, 2016
Messages
6
hello all,

I'm just getting into DIY flashlights using convoy hosts. I'm currently looking to build, a green led beamed light, i have a few friends that are film students that expressed the desire for one and figure i would try to build them one. for giggle it will be going into a green convoy S+ with either a 18350 host or 18650 host.

these are the parts that i intend to use, can someone point out any flaw in the driver or emitter that I am missing?

https://www.fasttech.com/products/4963301 emmiter

https://www.fasttech.com/products/1122400 driver(i plan on grounding star 3 for low,med,high)
 
Last edited:

DrafterDan

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Jul 28, 2013
Messages
1,317
Location
Phoenix, AZ
For some reason, I see the 5-pack page from both web links.

Those have a 3 to 3.6v input, so a rechargeable is out of the question, as they charge to 4.2 volts and run a nominal 3.7 volts. Can you correct the link so we can see which driver you are thinking about?

***Edit
I punched in the item number, that came up as this.
3* AMC7135 4-Group 2~5 Modes LED Flashlight Driver Circuit (Nanjg AK-47A)

That has an output of 1.05 amp, so it should do the trick. Since you are buying a 5-pack of LEDs, why not see if it will work with a rechargeable? Worst case is you blow one up. Given that no circuit design is 100% efficient, I think it is worth a try, however the electronics were always my weak point in modifications.
 
Last edited:

DIWdiver

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Connecticut, USA
Well, electronics is my strong point so maybe I can take a stab at the issues.

The LEDs have a 3-3.6V "forward voltage". That means that at the rated current, the voltage across the LED will be 3-3.6V. It does not mean you can put 3.6V across it and expect it to survive. Unlike most electrical and electronic devices where the supply (battery, line voltage, generator, etc) decides the voltage, and the load (Lamp, radio, heater, etc) will pull some amount of current at that voltage, the LED wants to decide the voltage, and the supply has to decide the current. But the battery is crappy at deciding current. It wants to supply voltage. That's where the driver comes in. The driver turns the voltage source (battery) into a current source that the LED wants.

The output of the driver is connected to the LED, so we need to make sure the driver's output characteristics are suitable for the LED. The driver's input is connected to the battery, so the driver's input characteristics need to be matched to the battery.

The primary output characteristic of the driver is the maximum current. In this case it's 1.05A. The LED has a max current of 1000mA, or 1.00A. If I was being fussy, I'd say that these are incompatible, because the driver can supply too much current to the LED. If I was designing a product that had to run a lot and last a long time, I wouldn't do this. But in the modding world, Crees are often overdriven much more than this. The consequence is that you have to be really careful with heatsinking, and you can't expect a normal lifetime on the LED. If you are going to do a good job with the heatsinking, I'd say go ahead. Otherwise choose a lower-current driver.

The secondary output characteristic of the driver is the allowable voltage range. This is not always easy to find, but I know that driver is based on AMC7135 chips, and that the '7135 has an allowable output voltage (remember, the LED will be choosing the voltage) of zero to about 0.15V less than the input voltage. When the battery is fully charged, (about 4.0V on load), this translates to 0-3.85V, and the LED voltage is within this range, so we're golden. When the battery is discharged (3.0V, give or take depending on your battery and your preferences), the output range of the driver is 0-2.85V. Uh-oh. This means that at some point during the discharge, the driver won't be able to shove that 1.05A through the LED any more. The light isn't going to suddenly go out, but the current (and therefore the light output) will start dropping. I think with these components it would continue to drop all the way to zero. Some drivers will suddenly shut off at some point, but I don't think this one would.

The input characteristic of the driver is it's allowable voltage range (the battery will be determining the actual voltage). This driver says 3.0-4.5V. That fits well with our battery. This assumes you use a typical "3.7V" lithium-ion rechargeable battery. Other lithium batteries are lower voltage and so not well suited to these components.
 

gundles123

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Joined
Oct 3, 2016
Messages
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Well, electronics is my strong point so maybe I can take a stab at the issues.

The LEDs have a 3-3.6V "forward voltage". That means that at the rated current, the voltage across the LED will be 3-3.6V. It does not mean you can put 3.6V across it and expect it to survive. Unlike most electrical and electronic devices where the supply (battery, line voltage, generator, etc) decides the voltage, and the load (Lamp, radio, heater, etc) will pull some amount of current at that voltage, the LED wants to decide the voltage, and the supply has to decide the current. But the battery is crappy at deciding current. It wants to supply voltage. That's where the driver comes in. The driver turns the voltage source (battery) into a current source that the LED wants.

The output of the driver is connected to the LED, so we need to make sure the driver's output characteristics are suitable for the LED. The driver's input is connected to the battery, so the driver's input characteristics need to be matched to the battery.

The primary output characteristic of the driver is the maximum current. In this case it's 1.05A. The LED has a max current of 1000mA, or 1.00A. If I was being fussy, I'd say that these are incompatible, because the driver can supply too much current to the LED. If I was designing a product that had to run a lot and last a long time, I wouldn't do this. But in the modding world, Crees are often overdriven much more than this. The consequence is that you have to be really careful with heatsinking, and you can't expect a normal lifetime on the LED. If you are going to do a good job with the heatsinking, I'd say go ahead. Otherwise choose a lower-current driver.

The secondary output characteristic of the driver is the allowable voltage range. This is not always easy to find, but I know that driver is based on AMC7135 chips, and that the '7135 has an allowable output voltage (remember, the LED will be choosing the voltage) of zero to about 0.15V less than the input voltage. When the battery is fully charged, (about 4.0V on load), this translates to 0-3.85V, and the LED voltage is within this range, so we're golden. When the battery is discharged (3.0V, give or take depending on your battery and your preferences), the output range of the driver is 0-2.85V. Uh-oh. This means that at some point during the discharge, the driver won't be able to shove that 1.05A through the LED any more. The light isn't going to suddenly go out, but the current (and therefore the light output) will start dropping. I think with these components it would continue to drop all the way to zero. Some drivers will suddenly shut off at some point, but I don't think this one would.

The input characteristic of the driver is it's allowable voltage range (the battery will be determining the actual voltage). This driver says 3.0-4.5V. That fits well with our battery. This assumes you use a typical "3.7V" lithium-ion rechargeable battery. Other lithium batteries are lower voltage and so not well suited to these components.

The allowable output voltage is what I couldn't find, I figured the .05 amps was negligible. Basicly the heatsink will have to make up for over driving the led till the battery voltage drops enough to push driver out put to match the led and then at some point as the voltage drops the led will dim at a undetermined rate until the low voltage flash. I'm good with that, I can't foresee it being used for more than a few minutes at a time. Thanks for the help!
 

irongate

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Joined
Apr 17, 2016
Messages
372
Location
Rochester Mn.
Well, electronics is my strong point so maybe I can take a stab at the issues.

The LEDs have a 3-3.6V "forward voltage". That means that at the rated current, the voltage across the LED will be 3-3.6V. It does not mean you can put 3.6V across it and expect it to survive. Unlike most electrical and electronic devices where the supply (battery, line voltage, generator, etc) decides the voltage, and the load (Lamp, radio, heater, etc) will pull some amount of current at that voltage, the LED wants to decide the voltage, and the supply has to decide the current. But the battery is crappy at deciding current. It wants to supply voltage. That's where the driver comes in. The driver turns the voltage source (battery) into a current source that the LED wants.

The output of the driver is connected to the LED, so we need to make sure the driver's output characteristics are suitable for the LED. The driver's input is connected to the battery, so the driver's input characteristics need to be matched to the battery.

The primary output characteristic of the driver is the maximum current. In this case it's 1.05A. The LED has a max current of 1000mA, or 1.00A. If I was being fussy, I'd say that these are incompatible, because the driver can supply too much current to the LED. If I was designing a product that had to run a lot and last a long time, I wouldn't do this. But in the modding world, Crees are often overdriven much more than this. The consequence is that you have to be really careful with heatsinking, and you can't expect a normal lifetime on the LED. If you are going to do a good job with the heatsinking, I'd say go ahead. Otherwise choose a lower-current driver.

The secondary output characteristic of the driver is the allowable voltage range. This is not always easy to find, but I know that driver is based on AMC7135 chips, and that the '7135 has an allowable output voltage (remember, the LED will be choosing the voltage) of zero to about 0.15V less than the input voltage. When the battery is fully charged, (about 4.0V on load), this translates to 0-3.85V, and the LED voltage is within this range, so we're golden. When the battery is discharged (3.0V, give or take depending on your battery and your preferences), the output range of the driver is 0-2.85V. Uh-oh. This means that at some point during the discharge, the driver won't be able to shove that 1.05A through the LED any more. The light isn't going to suddenly go out, but the current (and therefore the light output) will start dropping. I think with these components it would continue to drop all the way to zero. Some drivers will suddenly shut off at some point, but I don't think this one would.

The input characteristic of the driver is it's allowable voltage range (the battery will be determining the actual voltage). This driver says 3.0-4.5V. That fits well with our battery. This assumes you use a typical "3.7V" lithium-ion rechargeable battery. Other lithium batteries are lower voltage and so not well suited to these components.

Nice write-up for explaining all that.Thank You
 

gundles123

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Joined
Oct 3, 2016
Messages
6
Yes, thank you DIWDiver, This actually explains a few questions that i was going to ask. this kind of information should be stickyd in this forum
 

Blitzwing

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Apr 15, 2009
Messages
415
Location
Straya
I've built a few P60 modules and a C8 using this:

https://www.fasttech.com/products/1...-xp-e-1w-520-530nm-green-light-led-emitter-on

And this:

https://www.fasttech.com/p/1127404

m5WNNTa.jpg
 

gundles123

Newly Enlightened
Joined
Oct 3, 2016
Messages
6
nice, i was looking for the single pack. i already ordered(and it shipped) the links that i posted. ill make sure to update this when i get it in and built.
that looks like what im after though
 
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