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

[Maros]

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.

 

[AUTO XX]

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]

What exactly is the point of a test load? I've seen a few people mention them.

 

[AUTO XX]

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.

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

 

[Maros]

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?

 

[AUTO XX]

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.

 

[anselm]

LM350 is just rated to 5 amps instead of 1 (LM317).
You won't get any reading unless you use a dummy load.

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]

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.

 

[AUTO XX]

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]

Ofcourse radio shack doesn't sell 1ohm resistors. 10 ohm 1/2watt or 1 ohm 10 watt

 

[AUTO XX]

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]

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.

 

[Maros]

WTS Resistors!

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

I know, I post too much.

 

[AUTO XX]

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]

True. I'm mostly just frustrated with vendors not the project lol.

 

[Maros]

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!

Finished drive, except that 1kohm demon pot (I hate that thing so far).