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 Laser Pointer Forums - Discuss Laser Pointers DX200 circuit info

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07-11-2008, 02:36 AM #1
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CHP
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DX200 circuit info

I just got one before the price drop. I took it apart and traced some of the power circuitry. The circuit is basically a op amp / PNP transistor current regulator. The attached circuit shows the power stage.

The 6.2 ohm resistor and 220uF capacitor slow down the batteries' dV/dt when the switch is closed and helps to eliminate the initial current spike that can typically happen with this type of current regulator. The problem is the voltage drop across the 6.2 ohm resistor. With my batteries, the voltage applied to the circuit is about 5.5 volts at about 270 mA. With 270 mA there is a 1.67 volt drop across the 6.2 ohm resistor which leaves 3.83 volts to power the regulator circuit (5.5 - 6.2 x .27). The sense feedback resistor is 1.5 ohms which drops another 0.41 volts (.27 x 1.5) leaving 3.42 volts to power the LD and the Vce for the PNP transistor. If the LD drops about 3 volts at 270 mA then there is about 0.42 volts across the PNP transisor which puts it in saturation and unable to regulate the output current. In order for the regulator to work the voltage needs to be higher.

To get more power from mine, I simulated the circuit and compared data from varying the supply voltage and measuring the conducted current. After I got agreement, I simulated a 10 ohm resistor in parallel with the 6.2 ohm resistor. Then I soldered a 10 ohm resistor in parallel with the 6.2 ohm resistor. Now my current is about 340 mA and burns much better.
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07-20-2008, 12:14 AM #2
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pseudolobster
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Re: DX200 circuit info

Awesome work!

awfully simple driver isn't it? by any chance do you have a power meter and would be able to test how much of an improvement that made?
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07-20-2008, 01:31 AM #3
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GamerBR
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Re: DX200 circuit info

The driver of the dilda was actually made to run on 3.6v CR2s,or they made it wrong,because mine works perfectly with 3.6v in CR2s but with the 3v ones it don't regulate the current well.Anyone that has it,it's better if you buy some 3.6V CR2s and regulate the pot so it's drawing about 330mA from the batteries,before using 3.6V changing the pot of mine did nothing,it would only turn the laser on and off,and while on it was drawing about 290mA from the batteries.

07-23-2008, 10:48 PM #4
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Re: DX200 circuit info

Quote:
 Originally Posted by pseudolobster Awesome work! awfully simple driver isn't it? by any chance do you have a power meter and would be able to test how much of an improvement that made?
I don't have a power meter. I'm guessing power just based on what I read here that the dx200 laser diode is about the same as the Mitsubishi LD that Dr. Lave shows on his laser diode round up graph.

07-28-2008, 06:08 AM #5
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GooeyGus
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Re: DX200 circuit info

with proper batteries these lasers are always in spec. I've tested two in the last week using 3.6v cr2's that both did exactly 230mW. Pretty impressive!

07-28-2008, 07:46 AM #6
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el-taco
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Re: DX200 circuit info

Does anyone know where to acquire 3.6V rechargable CR2s by any chance?

07-29-2008, 11:37 AM #7
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Zom-B
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Re: DX200 circuit info

The same place the dilda laser came from, DX. Expect multi-month shipping times. I don't know any other place as these batteries are rare in my country.
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07-30-2008, 07:26 AM #8
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deebix
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Re: DX200 circuit info

thanks for the info man

07-30-2008, 09:05 AM #9
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el-taco
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Re: DX200 circuit info

Quote:
 Originally Posted by Zom-B The same place the dilda laser came from, DX. Expect multi-month shipping times. I don't know any other place as these batteries are rare in my country.
DX dont have 3.6V rechargables.

07-30-2008, 01:06 PM #10
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styropyro
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Re: DX200 circuit info

Quote:
 Originally Posted by el-taco [quote author=Zom-B link=1215743775/0#6 date=1217331442]The same place the dilda laser came from, DX. Expect multi-month shipping times. I don't know any other place as these batteries are rare in my country.
DX dont have 3.6V rechargables.[/quote]
They charge to 3.6v though.
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08-03-2008, 09:56 PM #11
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Re: DX200 circuit info

Quote:
 Originally Posted by styropyro [quote author=el-taco link=1215743775/0#8 date=1217408723]They charge to 3.6v though.
Yes, but 3.6V batteries charge to 4.2V.. Every battery charges higher than their nominal rating. My dilda was never in regulation untill i gave it 3.6V CR2s..

I got my 3.6V CR2s from AW on CPF.. And some more from newexcite store.. But newexcite store is slower than DX and much less unresponsive..

I do not know what the current jumps to if you put 3.6V batteries in without adjusting the pot first. I lowered mine and then raised it again to 330mA.. That's also what i suggested to GamerBR when i gave him the same CR2s, to prevent killing his diode. But when i gave some to someone else, they didn't lower the current first, and it came out at 440mA!

I wonder how long this diode can take it. It's still working for now.

In my case, the current before this was 300mA max, but more like 270mA and dropping.

It is possible, that in the factory the current is set with 3V batteries or a 6V supply, since they intend for it to be used with primaries. In this case, the current could actually be set MUCH too high, but it doesn't show cos it's not in regulation. Once you put in 3.6V, it will jump to whatever it is actually set to, and could kill the diode.
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08-03-2008, 09:59 PM #12
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IgorT
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Re: DX200 circuit info

Quote:
 Originally Posted by GooeyGus with proper batteries these lasers are always in spec. I've tested two in the last week using 3.6v cr2's that both did exactly 230mW. Pretty impressive!
Did you also measure the current draw by any chance?
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08-04-2008, 07:35 AM #13
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Re: DX200 circuit info

Quote:
 Originally Posted by IgorT [quote author=GooeyGus link=1215743775/0#4 date=1217225306]with proper batteries these lasers are always in spec. I've tested two in the last week using 3.6v cr2's that both did exactly 230mW. Pretty impressive!
Did you also measure the current draw by any chance?[/quote]

Yessir! It was about 330mA if I recall....

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