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How much press fit for a laser Diode?

reloader45

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Hello,

I finished my first copper heatsink for a 5,6 mm laser Diode. I drilled a 5,5 mm hole, followed by a light cut in my lathe.
With the digital caliper, i measured a Diameter of aprox. 5,60 mm.
I had luck, that i got a pressfit of my Diode in this heatsink.
My question is, how much is the ideal undersize of the bore for a pressfit in a copper heatsink?
Is it 1/100 mm, 2/100 mm or more?
I ask this, because i will grind a "reamer" from a 6 mm milling cutter.
Or is it the better way to drill the copper to 5,5mm and than calibrate the hole with a hardened steal rod on a hydaulic press?


best regards

Edgar
 



reloader45

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Hello,

thank you, that helps a lot. I think, a good pressfit is important for the heat transfer. But too much press will damage the Diode.


best regards

Edgar
 

paul1598419

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It is best to have a shelf that the diode's outer ring can press against. If you have an AixiZ type module to compare against this becomes obvious. Not all of the heat is transferred by the edge of the diode.
 

reloader45

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Hello Paul,

today I got my DTR copper module, now I understand what you mean with shelf. I think, I have to improve the heat transfer from the diode to the heat sink.
At the moment , I have an other problem. Today I also got my 5A laser driver:


I used my laboratory power supply to generate the 0 to 5 V, needed for the power control.

Is there any easy way to generate this voltage from the 12 V on this driver board?

best regards

Edgar
 

paul1598419

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Hello Paul,

today I got my DTR copper module, now I understand what you mean with shelf. I think, I have to improve the heat transfer from the diode to the heat sink.
At the moment , I have an other problem. Today I also got my 5A laser driver:


I used my laboratory power supply to generate the 0 to 5 V, needed for the power control.

Is there any easy way to generate this voltage from the 12 V on this driver board?

best regards

Edgar
I would look for a +5 volt wall wart, but if you are pulling a full 5 amps it might be difficult to find. If not, you should be fine at around 2 amps, but trying to use a +12 volt supply and using a DC/DC converter to make it work is just too complicated.
 

reloader45

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Hello,

the laser driver has a 12 V power supply. I need a low power, variable voltage from 0,7 to 5 V to regulate the power output of the analog driver. So maybe a 5V IC regulator and a potentiometer will do the job. Or a 5 V Zener diode with an potentiometer or something similar. Unfortunately i have more experience on the mechanical side than on the electronic side.


best regards

Edgar
 

paul1598419

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Okay. I now see what you are talking about. The +5 volts is used at the TTL input to turn the driver on and off. This only needs to be very low power as it takes very little current to control this input. Actually, I believe you can just use ground to turn the driver off as it doesn't need the +5 volts to that input to work. So, you really don't need a +5 volt source.
 

reloader45

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hello,
This Laser driver has an analog Input. Without Voltage on the Input, the Laser is off. This is different to the TTl Input.

Best regards

Edgar
 

paul1598419

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Hmmm. It says in the features that it is a TTL input and should be modulated at 20 KHz. I don't have one in my possession, so if you say it doesn't work like that I'll have to take your word for it.
I would just use a +5 volt wall wart if you need an external +5 volts.
 

Anthony P

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I have used other analog/pwm controlled power supplies. Not this one specifically. Usually they take a 5k pot from ground to 5v+ and the wiper is the input... 3 terminals. I realize this is not your answer, but it may point you in the right direction.
 

reloader45

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Hello,

I also asked the seller for further information, but they are only seller. They sell both, ttl and analog drivers. So the descpription is a mixture of both types.

Hello Anthony, what do you mean, the wiper is the input? Do you mean the middle contact of the poti ?
Unfortunately i have no 5V Voltage on this driver, but i can take the 12 V and add an 7 V Zener Diode.

best regards

Edgar
 

paul1598419

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If the input is truly analog you can modulate the output with the voltage. But, if it is TTL, then you will need a PWM to modulate it. The features describes it as TTL and recommends modulating at 20 KHz.
 

Anthony P

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Hello,

I also asked the seller for further information, but they are only seller. They sell both, ttl and analog drivers. So the descpription is a mixture of both types.

Hello Anthony, what do you mean, the wiper is the input? Do you mean the middle contact of the poti ?
Unfortunately i have no 5V Voltage on this driver, but i can take the 12 V and add an 7 V Zener Diode.

best regards

Edgar
Yes ,the middle contact. That varies voltage from 5v to 0. The power supplies I have worked with always had a built in 5v source. If yours has a 5v port I do not know. Listen to Paul... He is more experienced than I am.
 

reloader45

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Hello Paul,

yes I can modulate my Output power with a Voltage between 0V and 5V. I tested this with a laboratory power supply.
Today I will check if I can find a 5 V source on this Driver.

And please, don`t trust these chinese ebay descriptions blind, otherwise you can also order a cheap 10 000 mW 532 nm laserpointer from China.


best regards

Edgar
 




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