Understanding the simplicity of Daedal's circuit

[o_DEATH_ANG3L_o]

Ok this is for anyone who even thinks about hooking their LD directly to a power source. First off I would like to thank Daedal for this genius design. Also every member that has helped me along the way with my troubles. You know who you are. Ok so I went to RadioShack today and bought all the components for this circuit. Total cost: $9.77. Here is what I bought that added up to this price. The parenthesis include the RadioShack part number:

1. 5 pack of 10 Ohm resistors ($0.99) (271-1101)
2. 2 pack of 1N4001 silicone diodes ($0.59) (276-1101)
3. 47 uF electrolytic capacitor ($1.19) (272-1027)
4. 25 Ohm Rheostat ($3.99) (271-265)
5. LM317T voltage regulator ($2.29) (276-1778)

Ok now knowing this I think everyone should build one of these for the fact that an extra $9.77 will save your $17.00 LD. I have some pictures of this circuit built and with a meter hooked in series with a white LED. Here is a picture showing the setup with a bread board:

On the far right is just a PSU I scrapped from a DVD player. It puts out 9.75 volts. In the next pictures I show the current that a white LED is drawing at max resistance of the 25 ohm rheostat and at least resistance. Ok so following picture is maximum resistance pulling only 35.9 mA:

Next showing least resistance pulling 121.9 mA:

Now unfortunately I cannot test a an LD because well I do not have one. But all I know is this circuit is great. Build it! Don't risk your LD and listen to that moron Kipkay about the mini mag flashlight hack. You will DESTROY your LD and quick. Well I hope this can clear up a few concerns regarding Daedal's circuit and why NOT to hook an LD directly to AA's or AAA's.

 

[Gazoo]

Re: Understanding the simplicity of Daedal's circu

Glad you went that route. It just goes to prove this circuit is not as complicated as some make it out to be..(not you). Anyone can build it.

Now that you have come this far, I would recommend buying a PC board from RS and soldering everything. Breadboards are great for design and testing, but I do not recommending using them for the LD because they don't provide good connections.

Another thing you can do is put a 1 ohm resistor in series with the LD. When you measure the voltage across the resistor, you will get the same reading as if you were using your meter to measure current. You can even try this with your 10 ohm resistor and LED's. Needless to say, this eliminates the risk of damaging the diode due to a bad connection with your meter... when measuring current with it.

 

[o_DEATH_ANG3L_o]

Re: Understanding the simplicity of Daedal's circu

Yes I would definitely not hook an LD to this breadboard. I am going to solder everything up once I get a PC board. Now I am curious to see what a 130mA LD would measure in current at maximum resistance. But yes this circuit is genius as you can input any voltage from 6 to 30 volts at 1A. Or is it 2A? I forget but yeah Gazoo that DVD power supply will do me some good after all. I am using it to power this circuit for the LD. I am running it at 9.75 volts. You said something about putting a resistor in series with the LD. Now do you mean permanently or just for testing purposes? If it is just to test then what do you mean by get the same reading across the resistor as if I were using my meter to measure current?? You mean use the voltage setting on the meter and then test the resistor?? I didn't quite follow you there. Well if you can further elaborate on that I would appreciate it. Also thanks for replying, and hopefully more people who just want the easy way out hooking an LD straight to AA batteries will come and read this. Lol like there aren't a million posts about NOT doing it that way.

 

[Gazoo]

Re: Understanding the simplicity of Daedal's circu

Yes, you have it correct about the resistor. When you measure voltage across it using the voltage setting of your meter, it will give you the same reading as if you were measuring current. And you will have a more accurate reading since the meter does effect the circuit some when measuring current with it, but not as much as when using the 10 amp scale.

I like the resistor method so much it is all I use to measure my TEC cooled open can diode.

 

[Things]

Re: Understanding the simplicity of Daedal's circu

thanks for the post on how much a good cicuit can make a difference, and for $10, how could you not build it! and besides, this circuit is so simple, that even putting the diode into the module would be hrder to do! even though that is easy to ;D

 

[Benm]

Re: Understanding the simplicity of Daedal's circu

1. 5 pack of 10 Ohm resistors ($0.99) (271-1101)
2. 2 pack of 1N4001 silicone diodes ($0.59) (276-1101)
3. 47 uF electrolytic capacitor ($1.19) (272-1027)
4. 25 Ohm Rheostat ($3.99) (271-265)
5. LM317T voltage regulator ($2.29) (276-1778)

You are really paying way too much for these components though. Just as an indication, these are the prices one of my dutch suppliers charges for these items:

1. resistors, 0.05 each or 2.00 for a bag of 100
2. 1n4007 - 0.02 each
3. elco 100uF/25V - 0.04 each
4. 4W wire-wound 25 ohm pot - 3.50 (this is an unusual component)
5. LM317 - 0.20 in TO-92, 0.30 in TO-220 case

Not to bash radioshack, but you could save lots when you shop around for components. Apart from that pot, this circuit can be built for $1... and still save your $$$ diode

 

[BlueFusion]

Re: Understanding the simplicity of Daedal's circu

EXCELLENT!!   Glad to see you got the hang of it. Very good setup; I need to try something like this. Also 121 mW would be fairly good for driving the LD at a very safe level, with good burning power.

Just make sure the circuit can't supply any more. Try putting 2 (or more) of those LEDs in parallel to draw more current.
It could be that 120mW is just the max current draw of that LED.

This deserves sticky! IMO mods

 

[Daedal]

Re: Understanding the simplicity of Daedal's circu

Death Angel;

Thank you for the very nice and objective post It's great to see it from another person's perspective ob how simple this really is

Although... I wanted to point out something (I don't remember the other thread about your incredible PSU find)... don't you think 9.75V is too much for a LD? Even for that poor LED... :-?

--DDL

 

[Robk]

Re: Understanding the simplicity of Daedal's circu

I don't know if this post belongs here, but it's about SenKat's diodes and Daedal's circuit, so I guess it fits. I'm still looking for a host flashlight ( I have a few, but I'm reluctant to destroy them!) to put this thing in. Trying to keep things small, I used a SMD 22uF across the diode, barely visible in the photos, fixed resistor for the LM317 (to be replaced with a SMD 5 ohm resistor when I can locate one) and I ground down the LM317 to eventually fit into the rear metal casing screwed back on. It's pulling about 240mA total from a 6V power source, about 160mA from 4 NiMH AAs (not enough). I haven't measured actual current to the diode - can't get to it now as it's buried. I think measuring the voltage across the 5 ohm resistor will give me a fairly close idea of the drive current, but the LM317 is drawing some current also which will prevent an accurate measurement. But, to get to the point, this diode that I got 2 days ago is BRIGHT! Much hotter than others I have harvested from DVD drives. Daedal's circuit works well, simple but effective, thank you for developing it for this purpose. I just wish the voltage drop wasn't 1.25V, kinda blows the idea of 4 NiMH cells. I may try a different IC with less overhead. Here's a few photos of the beast ready for planting in a 2 x CR123 host. I thought someone may be interested in a smaller way to construct Daedal's driver. And, thanks Greg for the diodes - they work great, and as I said, they are hot!!

Hope the photos show up - I got a message I can't post links (to my site)

tomokadesigns.com/laser1.jpg
tomokadesigns.com/laser2.jpg

Rob

edit: trying again

 

[o_DEATH_ANG3L_o]

Re: Understanding the simplicity of Daedal's circu

Death Angel;

Thank you for the very nice and objective post It's great to see it from another person's perspective ob how simple this really is

Although... I wanted to point out something (I don't remember the other thread about your incredible PSU find)... don't you think 9.75V is too much for a LD? Even for that poor LED... :-?

--DDL

Didn't you say that this circuit is able to drive the LD with an input voltage of 6 to 30 volts?? Now I am scared. LOL but could you elaborate on what you meant by that? Ok so with this circuit, what is the best input power source to use? Batteries? What kind and size? AC to DC wall converter? I am just trying to clear up final confusions here. I thought I had it. But Daedal you said something about my 9.75 volt PSU is a bit much for the LD . Well I hope you understand what I mean. Thanks for the feedback also.

 

[Gazoo]

Re: Understanding the simplicity of Daedal's circu

Well I commend you on a job very well done. .. Better than I have done so far as far as keeping it small.. ;D

Actually the voltage drop of the 317 is closer to 2 volts. You really want to keep the voltage at 6 volts or more. As you know there are other regulators out there that are much more efficient with much lower drop out voltages.

I was looking at the AMC7135. It has a drop out voltage of only 120mv, and is rated at 350ma's.

 

[Gazoo]

Re: Understanding the simplicity of Daedal's circu

[quote author=Daedal link=1189718300/0#7 date=1189729801]Death Angel;

Thank you for the very nice and objective post It's great to see it from another person's perspective ob how simple this really is

Although... I wanted to point out something (I don't remember the other thread about your incredible PSU find)... don't you think 9.75V is too much for a LD? Even for that poor LED... :-?

--DDL

Didn't you say that this circuit is able to drive the LD with an input voltage of 6 to 30 volts?? Now I am scared. LOL but could you elaborate on what you meant by that? Ok so with this circuit, what is the best input power source to use? Batteries? What kind and size? AC to DC wall converter? I am just trying to clear up final confusions here. I thought I had it. But Daedal you said something about my 9.75 volt PSU is a bit much for the LD . Well I hope you understand what I mean. Thanks for the feedback also.[/quote]

You are fine. What he meant is you can power it with a lower voltage and it will be more efficient as far as the LM317 goes. The more voltage applied to the LM317, the harder it works to regulate current...therefore it will probably get quite hot. BUT, the LM317 has built in thermal protection. So you really have nothing to worry about. If you plan on running your LD for long periods of time, then you should get a heat sink for the LM317. I use small ones that simply clip onto it.

 

[Daedal]

Re: Understanding the simplicity of Daedal's circu

Robk, THAT is an incredible shrinking effort. I salute your efforts and setup. Excellent indeed

Nice work, and thank you for sharing;
DDL

 

[Daedal]

Re: Understanding the simplicity of Daedal's circu

[quote author=Death Angel link=1189718300/0#9 date=1189731275][quote author=Daedal link=1189718300/0#7 date=1189729801]Death Angel;

Thank you for the very nice and objective post It's great to see it from another person's perspective ob how simple this really is

Although... I wanted to point out something (I don't remember the other thread about your incredible PSU find)... don't you think 9.75V is too much for a LD? Even for that poor LED... :-?

--DDL

Didn't you say that this circuit is able to drive the LD with an input voltage of 6 to 30 volts?? Now I am scared. LOL but could you elaborate on what you meant by that? Ok so with this circuit, what is the best input power source to use? Batteries? What kind and size? AC to DC wall converter? I am just trying to clear up final confusions here. I thought I had it. But Daedal you said something about my 9.75 volt PSU is a bit much for the LD . Well I hope you understand what I mean. Thanks for the feedback also.[/quote]

You are fine. What he meant is you can power it with a lower voltage and it will be more efficient as far as the LM317 goes. The more voltage applied to the LM317, the harder it works to regulate current...therefore it will probably get quite hot. BUT, the LM317 has built in thermal protection. So you really have nothing to worry about. If you plan on running your LD for long periods of time, then you should get a heat sink for the LM317. I use small ones that simply clip onto it.
[/quote]

Not quite what I was referring to Gazoo...

The LM317 drops the voltage by whatever it needs, but then the rest is forwarded onto the load. In the case of a 9.75V input, a minimum of 6.75V will be forwarded onto the LD. I would suggest a 6V input because when it drops by 6V, you get 3V to the LD. It is true that the LD will take only what it needs, but the rest will generate extra heat. That could be either by the LD or by the LM.

GL;
DDL

 

[Gazoo]

Re: Understanding the simplicity of Daedal's circu

Yes...I do understand that Daedal. However, I have mine adjusted so the current to my LD is 250ma's. I have 6 volts going into the circuit. If I apply 7.5, 9, or 12 volts to the input of my circuit, the current going to the diode and the voltage across the diode does not change. So....all that excess current IS being dissipated by the LM317T and not the diode.

 

[Daedal]

Re: Understanding the simplicity of Daedal's circu

It is true that LD's act just like any other diode. They cause a voltage drop in the circuit.

Perhaps you are right about the diode not taking any of the extra voltage, and I would assume and I verified that your measurements are correct.

I'll have to figure out eventually where that extra voltage is going... I'm too sleepy to think now... ;D

--DDL