Old 08-22-2011, 10:39 PM #1
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Post DIY driver help

so i read the thread about diy drivers, and i have a few questions.

Lets say i want to power a 445nm diode up to 1000ma. would i need to put one 1 ohm resistor or ten 10 ohm resistors?


Edit: Also would it be better to just buy a driver to power the diode?



Last edited by furrylaser; 08-22-2011 at 10:39 PM.
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Old 08-22-2011, 10:42 PM #2
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Default Re: DIY driver help

r = v/i

lets sat you feed it 4.5 volts and you want to drive it at 1 amp

r = 4.5/1

You need a 4.5 ohm resistor to drive a diode at 1 amp assuming your voltage is 4.5 volts.

EDIT:
If you have 2x 10 ohm resistors on hand, put them in parallel (or 5x 1 ohms in series) and that will give you a 5 ohm resistor

Last edited by Jacob32123; 08-22-2011 at 10:47 PM.
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Old 08-22-2011, 11:27 PM #3
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Default Re: DIY driver help

What driver are you thinking of using, mister furrylaser?

Quote:
Originally Posted by Jacob32123 View Post
r = 4.5/1
V should be the voltage drop across the resistor, not the supply voltage.

What about if the supply voltage was 2V and we used that equation? It would suggest 2 ohms when in fact NO value of resistor will will allow any current through the diode, because 2V isn't enough.

The forward voltage of a 445nm at 1A is about 4.5V. So if your supply voltage was 4.5V, you wouldn't need a resistor.

That's theory, but in the real world, you cannot be sure that either the voltage of the diode or the voltage of the power supply will be exactly 4.5 all the time, and small changes in voltage make for large changes in current.
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Last edited by Cyparagon; 08-22-2011 at 11:32 PM. Reason: added info
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Old 08-22-2011, 11:40 PM #4
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Default Re: DIY driver help

I was thinking about making my own driver, using a LM317 regulator. Also which kind of variable resistor would i need on it? This is my first "high" powered laser.
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Old 08-23-2011, 12:02 AM #5
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Default Re: DIY driver help

i also have another question, how do you short out a capacitor?
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Old 08-23-2011, 12:12 AM #6
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Default Re: DIY driver help

Quote:
Originally Posted by furrylaser View Post
i also have another question, how do you short out a capacitor?
short out the negative and positive leads aka rub the wires together
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Old 08-23-2011, 01:59 AM #7
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Default Re: DIY driver help

the wires going to the diode or to the battery?

also do you have to do this everytime after you set the current with a test load?
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Old 08-23-2011, 02:15 AM #8
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Default Re: DIY driver help

to the diode and im a little confused by your 2nd question
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Old 08-23-2011, 06:52 AM #9
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Default Re: DIY driver help

oh what i mean is when or how often do u have to short the capacitor
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Old 08-23-2011, 09:39 AM #10
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Default Re: DIY driver help

I rather not call you "furry," unless you are lol.
Anyway, I'm doing the same thing too. I just bought the beefiest potentiometer I could find. I think mine is a 5W wire wound pot lol. Not taking chances with the potentiometer frying and putting my power control out of commision. Anyway I've used it on my breadboard with no probs. try that.
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Old 08-23-2011, 12:44 PM #11
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Default Re: DIY driver help

Quote:
Originally Posted by furrylaser View Post
oh what i mean is when or how often do u have to short the capacitor
Before you hook up your diode
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Old 08-23-2011, 05:12 PM #12
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Default Re: DIY driver help

ok so i got a 1w 445 diode from 5.6mm 445nm ~1W laser diode [M0020] - $51.99 : Modwerx Shop and i pressed it into an aixiz module and am using a glass 445nm lens. Now for the driver, i was thinking about making one with the lm317 regulator. I just have a couple questions, how much voltage does the diode need? I am going to use a 9 volt power supply and how many resistors do i need rated at how many ohms?I used the r=v/i and so r=9/1.2 (i decided to power it at 1.2 amps) and got 7.5. So do i need a 7.5 ohm resistor? Also do i need a capacitor? Lastly i don't really get what a potentiometer does i think it regulates the current but then how do you know how high of a potentiometer you need?

thank you

Last edited by furrylaser; 08-23-2011 at 05:15 PM.
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Old 08-23-2011, 09:10 PM #13
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Default Re: DIY driver help

Quote:
Originally Posted by furrylaser View Post
ok so i got a 1w 445 diode from 5.6mm 445nm ~1W laser diode [M0020] - $51.99 : Modwerx Shop and i pressed it into an aixiz module and am using a glass 445nm lens. Now for the driver, i was thinking about making one with the lm317 regulator. I just have a couple questions, how much voltage does the diode need? I am going to use a 9 volt power supply and how many resistors do i need rated at how many ohms?I used the r=v/i and so r=9/1.2 (i decided to power it at 1.2 amps) and got 7.5. So do i need a 7.5 ohm resistor? Also do i need a capacitor? Lastly i don't really get what a potentiometer does i think it regulates the current but then how do you know how high of a potentiometer you need?

thank you
A potometer is a variable resistor
I'm on my way home from school and ill give you a link that will help a lot
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