Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

First Build / Experimenting - Suggestions on which direction to head next?

Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
Great info auto! exactly what I needed to hear. I wish I had a variable bench psu, unfortunatly i have the option of 12v or 5v. I may step down to 5 in this case though. I got the aixiz module today and am waiting on a new diode from modwerx, im out of burners to harvest from so it'll be a good week before any updates but hopefully I'm fairly well set to go when the diode comes in though. I figured I could throw a resistor in there but I like the idea of being able to adjust it too :).


**Edit**

I was just at radioshack, I didn't see any pots that would be low enough, but I did see one that was labled as a 25 ohm 3 watt reheostat (looks just like a pot), what exactly is that? would that work in this circuit? I like the idea of having a pot knob on the outside of the box.
 
Last edited:





AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
I hear ya about the adjustable resistance bro. I thought that would be pretty important when I first got into lasers.
Made two DDL circuits with pots and found that they got hot depending on the diode I was powering. The 445s are too much for a pot so I started making fixed resistor DDLs with a 1N540* diode, a 2W resistor and a LM350 instead of the LM317.
Everything worked great but they are hard to build small if you want to put it into a handheld.
Remember your Ohms law if you do chose fixed resistor values.
A 1ohm resistor will give ~1.25A, 0.5ohm will give you .625A etc.
I'd pick something about 1/3rd less than the maximum people have tried for a specific diode and just set it to that current, should give fairly long life before it kicks the bucket ;)
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
What exactly is the point of a test load? I've seen a few people mention them.
 
AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
think of a test load as a diode simulator.
The difference is: instead of producing light, it provides a load (and a bit of heat). If you screw up and hit it with 5 amps for a few seconds, instead of costing $50 for a diode, you go "oops" and fix your mistake.
If you are making drivers....I'd really recommend having a good one.
Most use low wattage resistors and diodes but I prefer to be able to leave mine hooked up for a while even with a high power build.
P1140057.jpg

P1140058.jpg

I made two with 1N4004 diodes and low watt rated resistors but they got hot REALLY fast with my 1st 445 build.

You really need to read this
Laser driver - It can be done
 
Last edited:
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
Gotcha, I understand a bit better now lol. That'll have to be my next project. i read a bit more on the lm317 circuit tutorial and I didn't see anywhere about stepping up the current. I'm getting 240mA when I'd like to get around 400mA+. I have a lpc 815 coming and I'd like to push it as close as I can. Any suggestions on getting this circuit up to 400mA? I know earlier you mentioned the LM333 I believe. I'm testing with my multimeter on the leads where the diode would go, I'm reading now and I guess I wont get a very accurate reading unless I have a dummy load on the 317? correct?
 
Last edited:
AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
LM350 is just rated to 5 amps instead of 1 (LM317).
You won't get any reading unless you use a dummy load.
For the LM317 (and LM350) the reference voltage is 1.25.
Divide 1.25 by the resistance.
1ohm resistor=1.25A
2ohm resistor=.625A (625mA)
3.125ohm=400mA
Its all math, you need to understand this stuff before you can make electronics that do what you want.
Search:
Dummy loads
DDL (or deadal I think) driver
Ohm's law - Ohm's Law
It took almost a month of solid reading a lot of experimenting to understand most of this with any reliability, don't expect to know it all overnight.
 
A

anselm

0
Joined
Nov 22, 2010
Messages
2,448
Points
0
AUTO XX said:
LM350 is just rated to 5 amps instead of 1 (LM317).
You won't get any reading unless you use a dummy load.
Click to expand...
Ahem....
LM317 is rated for 1.5A, not 1A.
You can get a reading without a dummy load, using nothing but a DMM.
It might be a bit less accurate though...
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
Yeah I took electronics for several years in highschool, But that doesn't seem to be helping much now lol. I don't remember half as much as I should. Anyway with my DMM only I get 12.16v 580mA / 5.08v 9.8A from my power supply. Still getting about 3v 240mA from the 317. I'm a bit lost... lol. I guess I'll try a dummy load today see if that does anything different. I really need to see at least 400mA to be comfortable with it.
 
Last edited:
AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
The DMM gets a current reading with its own resistor, I read on here a while back that it made the measurement too inaccurate to be trusted.
If you want to increase the current, you can add a fixed value resistor in parallel with your pot. You need to figure out the size you need though
*hint* Two 1ohm resistors in parallel have a resistance of 0.5ohms
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
Ofcourse radio shack doesn't sell 1ohm resistors. 10 ohm 1/2watt or 1 ohm 10 watt :(
 
AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
You'll probably have to find a company that sells electronic components if you don't want to get your stuff online.
Radio shack has only ever had one thing I needed and I had to modify it to suit my use.
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
I had read on here its possible to use with out a resistor. I this true? cause quite frankly im getting a bit annoyed lol. here's what i have atm.

Also I don't really get the adding of fixed value resistors, to increase current I need to add more resistance? I must be missing something.

IMG_20110120_184053.jpg
 
Last edited:
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
WTS Resistors!

Also thought It'd be fun to show my current work station in the middle of a move lol! :(

IMG_20110120_204116.jpg


IMG_20110120_204109.jpg


I know, I post too much.
 
AUTO XX

AUTO XX

0
Joined
Aug 13, 2010
Messages
839
Points
28
Might be easier to look at it this way:
The diodes dictate how much voltage will be used and the resistor uses current.
I know its frustrating but if there was no reason to do it a specific way, no one would be.
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
True. I'm mostly just frustrated with vendors not the project lol.
 
Maros

Maros

0
Joined
Dec 28, 2010
Messages
70
Points
0
I'm getting minute readings with this test load, hooked up the way this shows to.

1 ohm 1/4 watt 5% tolerance resistor, 1n4001 diodes

Sooo 3 1ohm resistors = 833mA?
1.25/1.5=.833x1000=833

*Edit*

Okay so! Drive is finished with the exception of replacing the 1kohm pot to a 100ohm pot (which I'll have to order).

Have the heat sinks being made up.

Host is on the way.

Diode is on the way.

Almost there!

IMG_20110120_220953.jpg


Finished drive, except that 1kohm demon pot (I hate that thing so far).
drive.jpg
 
Last edited:
You must log in or register to reply here.




Top