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Driver build problems

Jufran88

Jufran88

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Your driver should look like this:
11702-diy-homemade-laser-diode-driver-ld_driver_schematic.jpg

Ignore some of the values because I got this from Daedal's post

In your schematic it looks like your using (2) 1 ohm resistors in parallel, which doesn't give you the 10 ohms you need. (2) 1 ohm resistors in parallel will give you .5 ohms. You only need (1) 10 ohm resistor (buy them at radioshack).

The reason for this is because the resistors after the pot sets the limit for the current. I think you included the 100 ohm pot resistor in your calculations. It's just to adjust the current so it's neglible in your calculations.

Put the test load where the laser diode would be and measure the current on the test load resistor.

If this doesn't help here is a website I think will help you better: *Laser driver - It can be done*
 





Toke

Toke

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The reason for this is because the resistors after the pot sets the limit for the current. I think you included the 100 ohm pot resistor in your calculations. It's just to adjust the current so it's neglible in your calculations.
Click to expand...

(My bolding)
"Just to adjust the current" "Negligible"
What have you been smoking?

ETA:
Oops, I overlooked the pot in resistor. :(
Yes, you can ignore the pot when calculating max current, and include it for minimum current.
 
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BennyF

BennyF

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I need around 1.5 ohms to get the 800mA that i want at the end 10 ohms is gonna give me around 125mA i realize that's how its supposed to be and that's how i had it i just wasn't getting what i was supposed to on my output current wise. Looking into how the LM317 works it needs an amperage of over 1A on the power supply. my batteries since they are about dead are giving me 7V but only about 10mA so i'm thinking that's the issue. stupid me didn't get a battery charger when i got the batteries so i have to wait for one to get shipped. luckily i found a nice charger for a good price that will work with my batteries and it comes with two 18650's so hopefully this fixes the issue i'm having.
 
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Jufran88

Jufran88

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You don't need 1A to power the LM317. What it probably meant on the data sheet is it is limited to 1A current draw, but usually are capable of 1.5A. Working voltage for the LM317 is around 3V.

Remember, any unused voltage by the LM317 will be dissipated into heat.
 
BennyF

BennyF

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I have my driver set up like the links you showed me. I'm looking to gain around 800mA so i have a 1.5 ohm series parallel resistor cluster attached between the adj and the Vout. i only get around 50mV on the 1 ohm resistor on my load bank. i understand how this circuit works its just not working. if you look at the data sheet for the LM317 it will show you that the input current should but >(greater than)1A hence why i have to get a charger to charge my batteries. If that doesn't fix my problem i have no clue what I'm doing wrong then.
 
Jufran88

Jufran88

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What are the resistor values you are using in order to get the 1.5 ohms?
 
123splat

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BennyF - your last post about not enough current in is correct! Recharge your batt.s, set up like Toke has described and you should be O.K. Make sure that your 1 Ohm in the test load is actually 1 Ohm, otherwise you will have to recalculate current out from your meter reading. Good luck, stay with it, and listen to Toke.
 
BennyF

BennyF

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ok so i have my driver set up with a 1.5 ohm resister (3x1 ohms in series parallel) and i finally got my 18650's in the mail with the charger. whats promising is with about half charge they give me about 500mA so this looks like the problem is fixed. but now there is another i have now clue how im gonna arrange 2 18650's in a host..LOL. i didn't realize how big they were i just kinda figured they were the size of AA's. but at least my circuit should work.
 
Toke

Toke

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Good to hear. :)


There are AA sized ones, called 14500, the AAA's are 10440.

The lithium battery numbers parse as: diameter-lenght-shape.
In this case 14mm in diameter, 50mm long, and a 0 for cylindrical.
 
BennyF

BennyF

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well its done and i'm dubbing it the "Black Mamba". sitting right around 1W. it is currently in a temporary case until i can find a host or can build a case that i like. i will post pictures later, not only because i don't have my camera but because my batteries died from playing with it to much.
 
BennyF

BennyF

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Now remember this is only a temporary housing for the laser, so don't be so harsh.

DSC02305.jpg

DSC02306.jpg

DSC02308.jpg

DSC02307.jpg
 
A

anselm

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Hehe, nice!:)
Is that a custom jayrob 405-G1 lens? Judging from the spot's appearance.
Also, looks like you'd be better off with more heatsinking than what looks just an Aixiz module.
 
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