DDL driver

[DeathNoteViewer]

So i am making my first driver for a phr-803t diode. The schematic says that i need to solder a 10ohm resistor but i doesnt say of what wattage. So i went to my local electronics store and bought a 1/2w one. When i got home i found out that the clerk put a 1ohm one instead of a 10ohm. Money wasn't a matter since these things are dirty cheap, so i started looking in my electronics stash for a resistor of the said value. What i have found was a 10ohm@1/8watt one, but i don't know if it is suitable because of it's wattage. Does anybody know if it is ok?:thinking:

 

[anselm]

You can always try it out, check if the resistor heats up much.
If it does get very hot fast, you will need a physically bigger (more watt) one.
0.1Ax5V=1/2W, so a 10 ohm , 1/2W would be the ideal resistor.

 

[Elektrotechniker]

You could try with a 1 ohm resistor you bought. The ranges should be different, but you will most probably me able to get 100 mA. Try it out

 

[DeathNoteViewer]

What if i connect the resistor which is 10ohm@1/8w with the other that is 1ohm@1/2w in series?
I mean, the resistance won't change that much, but what about the wattage?

 

[anselm]

Yeah put them in series, that's even better, the heat is distributed over both resistors,
so it is less on either one.

You could try with a 1 ohm resistor you bought. The ranges should be different, but you will most probably me able to get 100 mA.

Just the 1ohm one would make for 1250mA, way too much for a phr!

 

[Cyparagon]

0.1Ax5V=1/2W, so a 10 ohm , 1/2W would be the ideal resistor.

I'm not sure where you got those numbers, but Vref is 1.25V.

P=IV and I=V/R, so:
P=V²/R
P=1.25²/10
P≈156mW

1/8W is 125mW, but you can go slightly over on them - especially if the duty cycle is low and/or you don't expect 20,000-hour lifespans.

You could try with a 1 ohm resistor you bought. The ranges should be different, but you will most probably me able to get 100 mA. Try it out

NO! You know better, sir. :tsk: 1 ohm will yield 1.3A which will kill the phr instantly.

Yeah put them in series, that's even better, the heat is distributed over both resistors,
so it is less on either one.

Yes, but not equally. According to KCL, the current will be the same in both resistors, but according to Ohm's law, the power dissipated across each will be I²R.

Vref/R=I
1.25V/11≈115mA in both resistors

0.115A²*10Ω ≈ 132mW, while:
0.115A²*1Ω ≈ 13mW

You're going 5% over on one, and 97% under on the other.

 

[anselm]

Thank you for that Cyparagon!:beer:
I had figured 5V because that's about the Vf of the PHR.
And 0.1A was roughly the current he wanted to drive the diode with.

I was always wondering why I was getting away with such small resistors in the DDL circuit.
^^This makes makes sense to me now, and I inderstand the lm317 a little bit better.

 

[DeathNoteViewer]

The diode is now burned, i didn't know that i had to discharge the cap in case i desoldered the diode :/
The 10ohm@1/8w resistor was cool during operation though
So now i am looking for a new diode, and a new module. Any suggestions?

 

[Leodahsan]

PHR?

for 10 bucks: www.rayfoss.com

MODULE?

405nm/445nm laser module housing w/glasses lens [OL1845-BL] - $10.50 : Welcome to O-Like.com, Your source for laser products (recommended, $10)
or DealExtreme: $3.95 Red Laser Module - Focusable Dot (3.5V~4.5V 16mm 5mW) (aixiz, $4)
both from china. If you want it fast: www.aixiz.net

 

[DeathNoteViewer]

PHR?

for 10 bucks: www.rayfoss.com

MODULE?

405nm/445nm laser module housing w/glasses lens [OL1845-BL] - $10.50 : Welcome to O-Like.com, Your source for laser products (recommended, $10)
or DealExtreme: $3.95 Red Laser Module - Focusable Dot (3.5V~4.5V 16mm 5mW) (aixiz, $4)
both from china. If you want it fast: www.aixiz.net

I am not going to buy from o-like again. Using their module made the laser look more like a flashight

 

[Leodahsan]

@DeathNoteViewer
I prefer a flashlight working, cool laser, than a pen style, overheated, burnt laser.


edit:
1w 445 on o-like: 60 second on 20 off
1w 445 on aixiz: 10 second on ~40 off
(not very precise measurements)

 

[DeathNoteViewer]

@DeathNoteViewer
I prefer a flashlight working, cool laser, than a pen style, overheated, burnt laser.


edit:
1w 445 on o-like: 60 second on 20 off
1w 445 on aixiz: 10 second on ~40 off
(not very precise measurements)

I don't mean that the host looks like a flashlight. The ray looked like the light of the flashlight. Completly out of focus and uncolliminated.
To conclude, that was the module i was using and i am not satisfied at all :undecided:

 

[Leodahsan]

uuh? what the hell?
then you got defective lenses. I use they and they are the bomb man!
I prefer it for canned diode as I can just mess with they and test'em faster, unlike aixiz that needs flamin' tools, which I don't have atm. diode thread lock you know.

 

[DeathNoteViewer]

So do you think that if i ask them, they will give me a new lense?
And by the way did the brass collar went all the way in the threads when you put the diode? Mine was off for like 2-3mm. But when i had no diode in the brass collar fitted perfectly.

 

[Leodahsan]

Well I don't know.. the module himself is good, and lenses aren't that expensive after all. Maybe..

The brass collar went all the way in my module, and the diode got very pressed into the module.

 

[DeathNoteViewer]

I suppose it is defective as you said before. I ll send them an email and ask for refund