help with ddl driver

[mattmagic100]

hey guys. i really need some help with this. i built the driver and i tried testing it out on an led but it just wont work. i guess i just soldered it wrong to the pcb board. im gonna post pics. please help me!! =]] thanks!
and im sry for the bad quality on the pictures but i lose my good camera.

ps- i followed this exactly the same way as it shows in the ddl driver tutorial section with the actual picture schematic.

pss- were it shows the resistors left pin out, its actually directly over the small red wire. i accidentally drew it to far to the left and then there is a blue wire directly above the resistor.

 

[Meatball]

1. What are you using as your input voltage?

2. Whats your current source's current capacity?

3. How much current are you trying to regulate on the output?

4. What color laser will this be for?

Get us that info, and we can better help you.

 

[mattmagic100]

okey doeky =]

well first of all. just to make things clear this is my first pcb haha. k back to the info.

1.im gonna be using a 9 volt battery but im makin a labby like xcreedx has. so shouldnt the voltage be divided?
2. daedal said that if you use only 1 10ohm resistor itll limit the current to 125mA and thats what i need
3. im tryin to get about 120mA but i dont have a multimeter and i dont have money to buy one so i was just gonna turn it up till it burns somethin
4. and a blu ray laser from a phr

THANKS!! =]]

 

[Meatball]

1. K, the 9 volts you'll be using with be enough voltage, but the battery will quickly deplete. I might Recommend an AC-> DC wall wart adapter instead since this is a labby build.

2. Good research, ditch the potentiometer, and buy one 1/2watt 10ohm resistor.

3. You won't REALLY need one if you know your resistance, which is 10ohms. 10ohms= 125mA as already stated.

4. K, ditch the LED, its voltage drop will be no where near what the Laser diode's voltage drop is. ~4.2V dropped, which means that if you need to get the required ~3V to make the diode lase, you need to provide it ~7.2V.

From what I hear, before trying again, ditch the pot, maybe replace the lm317 in case its bad, then if it still doesn't work on the LASER DIODE (not LED), then make yourself a Blu-ray laser test load and measure the current flow with the multimeter you will have just bought.

Are you going to use a fan?

 

[mattmagic100]

1.k but do you think maybe i can use 2 9 volt batteries? so i can keep the labby portable?
2/3. thank you! =]] i guess ill just stick with the 10ohm resistor. so if i turn the pot on all the way it wont go further than 125mA
4.can you kinda explain this a little more please? =]

and do you know any link to help me make the test load because i check the second link to make a test load and it only talked about a red diode test load. and i guess im buying a multimeter haha =P

and ya, im using a fan.

 

[Meatball]

1. Yes, you can use as many batteries as you want, but make sure they are all connected in parallel.

2. It would be best to ditch the pot altogether, however, if you insist on using one, then to make your pot go from higher resistance to ~10ohms, you would simply need a 10ohm pot, thus relieving the need for a series resistor.

4. basically, you can't use an LED as laser diode test load because there is a voltage drop difference between them. It will make your circuit behave way differently than if you actually had a laser diode on it.

to test a circuit like your without a laser diode, you need to make a laser diode test load, a series of electrical components that will behave LIKE a laser diode of your choice. A test load looks like this:

hope this helps

 

[mattmagic100]

okay. so.......
1. i get that =]
2. im confused about that
4.got that too =]]
and THATS PERFECT THANKS!!!do i have to use 3.7 volts for the test load? will this 1ohm resistor work cause for some reason i just cant find it anywhere.......

http://www.radioshack.com/product/index.jsp?productId=2062290

 

[mattmagic100]

also where can i get a 10 ohm pot?
iv looked through some places and i prefer to go out and buy them than to order.
thanks! =]]

 

[Meatball]

2. the pot and series resistor you have been shown to have in place in the circuit, are only there to adjust the current flow to the laser diode, so that the right level can be found during a test with a dummy load. You however, already kow how much current you are aiming for, thus, we can plus a SET amount of resistance (10ohms) instead of the variable amount, (10ohm resistor + Pot). So from what i see in your pictures, all you must do is remove the pot, and then connect the open end of the resistor to the middle (V out) pin of the lm317. That is what will give you your 125mA.

4. the 3.7V just came from those specific batteries that the rkcster driver uses. The lm317 circuit will take 6-9V. So you will simply use your 9V source. (9V batteries)

Don't use those resistors. That a wirewound 10 watt monster. Heres what you need, no more. If your radioshack doesn't have them in stock, you can have them ship it to the store, or straight to your home with free shipping.

http://www.radioshack.com/product/index.jsp?productId=2062309

(use just ONE of them)

It doesn't appear that the shack has 10 ohm pots though, you might have to go to digikey, or have someone order one for you.

Does this help? :/

 

[mattmagic100]

2. k awesome! but where does the other end of the resistor go to? should it follow the line of the yellow wire?
4.GREAT!! =]]
thats awesome! im sure theyll have them. =]
and screw it im just gonna go with the resistor =]]
yes this helps SSOOO MUCHH. =]
+1!!!!

 

[Elektrotechniker]

2. k awesome! but where does the other end of the resistor go to? should it follow the line of the yellow wire?
4.GREAT!! =]]
thats awesome! im sure theyll have them. =]
and screw it im just gonna go with the resistor =]]
yes this helps SSOOO MUCHH. =]
+1!!!!

Resistor goes in series with the diodes. Then, after you power the test load you measure the current across the resistor. If that's what you want to know.

 

[rog8811]

@mattmagic100....
A complete description of how to test the circuit may be found here,
http://www.rog8811.com/laserdriver.htm
A test load costs cents and will save dollars on blown laser diodes. A multimeter from radioshack will not cost a lot and is an invaluable tool when doing electronics like laser drivers.
You have done a lot of good work so far, a few more dollars invested will make the rest of it easy.

Regards rog8811

 

[mattmagic100]

Resistor goes in series with the diodes. Then, after you power the test load you measure the current across the resistor. If that's what you want to know.

umm i was actually askin where to put the 2nd resistor. if thats what meatball is saying? wait.....
@meatball, are you saying, keep my first resistor where it is and add the one in the link you gave me to the v pin in the lm317? and if thats it then i need to know where to put the other end of the 2nd resistor.
THANKS ANYWAY SILVERSHOT!!!

@mattmagic100....
A complete description of how to test the cicuit may be found here,
http://www.rog8811.com/laserdriver.htm
A test load costs cents and will save dollars on blown laser diodes. A multimeter from radioshack will not cost a lot and is an invaluable tool when doing electronics like laser drivers.
You have done a lot of good work so far, a few more dollars invested will make the rest of it easy.

Regards rog8811

okay. haha i guess im gonna be buyin a multimeter. haha THANKS ROG8811!! =]]

 

[Meatball]

nope, just one, 10ohm resistor will be used in the circuit. One end goes on the middle (V out) pin of the lm317, the other end will be connected to where your diode, capacitor, and laser diode, all make a connection, (on the positive side of the capacitor, and LD, and the negative side of the diode, the side with the gray stripe). The ADJ pin will also be a part of this electrical connection. Sorry I should've been more specific. Hope this helps!

 

[Meatball]

This should be a better help, Rog8811 I took this pict from your website, hope its ok with you!

Nevermind the 7.2V, and the RED diode shown.

Heres your circuit:

Now, you see the Pot? That will be gone. See the two 10ohm resistors? One of those will go. Where the 10ohm resistor connects to the pot, you will connect to the middle pin of the IC instead. See? Its really pretty easy.

 

[mattmagic100]

nope, just one, 10ohm resistor will be used in the circuit. One end goes on the middle (V out) pin of the lm317, the other end will be connected to where your diode, capacitor, and laser diode, all make a connection, (on the positive side of the capacitor, and LD, and the negative side of the diode, the side with the gray stripe). The ADJ pin will also be a part of this electrical connection. Sorry I should've been more specific. Hope this helps!

are you kidding? this is GREAT!!! youve been a great help!! i get it now =]]
i just have 1 more question.
can i use a 10ohm 1/4 watt resistor? or does it have to be 1/2 watt?
thanks!! =]]

This should be a better help, Rog8811 I took this pict from your website, hope its ok with you!

Nevermind the 7.2V, and the RED diode shown.

Heres your circuit:

Now, you see the Pot? That will be gone. See the two 10ohm resistors? One of those will go. Where the 10ohm resistor connects to the pot, you will connect to the middle pin of the IC instead. See? Its really pretty easy.

this is AWESOME!! thank you!! =]]