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 Laser Pointer Forums - Discuss Laser Pointers DIY Thermal LPM for under \$50

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12-01-2015, 03:17 AM #561
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gregma
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Quote:
 Originally Posted by MarioMaster Not the case here, if you have a laser beam with a power of 1 watt, if you pick off half of the beam you only have 500mW. Were that not the case you would break the laws of thermodynamics =P So for anyone skimming, the ENTIRE beam must be on the TEC for an accurate reading.
I stand corrected! Thank you for the clarification. I'll learn these things eventually.

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12-01-2015, 05:49 AM #562
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Hibro
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Re: DIY Thermal LPM for under \$50

Can some one please tell me if what is the preferred voltage and current of the TEC?

12-01-2015, 03:22 PM #563
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ARG
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Re: DIY Thermal LPM for under \$50

Quote:
 Originally Posted by Hibro Can some one please tell me if what is the preferred voltage and current of the TEC?
It's a balance. If the voltage is too high there will be some non-linearity problems to deal with because there are more junctions. If the voltage is too low you'll have to set the gain on your amplifier really high which will amplify unwanted noise.

Generally the lowest voltage you would want is about 1V.

12-07-2015, 01:50 AM #564
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gregma
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Re: DIY Thermal LPM for under \$50

Question about this new circuit. It's been quite a while since I've read them and there is one point that is confusing me trying to breadboard the circuit waiting for the pcb. I see several +9v and several -9v. I also see 9v1+, 9v2+, 9v1- and 9v2-. I'm thinking these last are the two separate 9v batteries But it looks like the + on 9v2 is connected to the - of 9v1?

12-07-2015, 03:21 PM #565
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MarioMaster
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Re: DIY Thermal LPM for under \$50

Quote:
 Originally Posted by gregma Question about this new circuit. It's been quite a while since I've read them and there is one point that is confusing me trying to breadboard the circuit waiting for the pcb. I see several +9v and several -9v. I also see 9v1+, 9v2+, 9v1- and 9v2-. I'm thinking these last are the two separate 9v batteries But it looks like the + on 9v2 is connected to the - of 9v1?
Yup that's correct. The new circuit requires two 9v batteries. They are used to provide a larger voltage span for the LM358. The old design had the output of the amp running right at the negative rail which although usually works can cause some voltage offset or an inability to fully zero the meter.

The two 9v wires are connected together so the second battery provides -9v to the LM358's negative rail input.
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12-14-2015, 08:27 PM #566
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Re: DIY Thermal LPM for under \$50

makes sense. Next question. I finally have all the components, and am ready to breadboard while I wait for the pcb. Any way to use say a wall wart rather than two batteries?

12-15-2015, 01:23 PM #567
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Re: DIY Thermal LPM for under \$50

Quote:
 Originally Posted by gregma makes sense. Next question. I finally have all the components, and am ready to breadboard while I wait for the pcb. Any way to use say a wall wart rather than two batteries?
There are a few options, you could use two wall warts (or a PSU with +/- voltage outputs)

The other option is to use an isolated switching converter, but these tend to be noisy and require extra filtering components. There are also charge pump type chips that will also do this.

You can use the isolated output and ground the positive output (9v2+), making the negative output negative to ground. That will be your 9v2-
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ILT 5500KR krypton only air cooled ion 100mW 647.1nm | ILT 5500AR argon only air cooled ion >300mW multiline
Omnichrome 643 air cooled Ar/Kr ion 10mW 676.4nm 647.1nm 568.2nm 488nm 476.2nm (high hours)
Spectra Physics 127 >30mW 632.8nm HeNe | Uniphase 1.5mW 543.5nm GreeNe
Coherent Innova 90 argon ion water cooled ??W (got plasma, alignment in progress)
Coherent 60W 830nm water cooled diode brick | Shenhui Laser 40W 10600nm water cooled CO2

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12-15-2015, 07:48 PM #568
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gregma
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Re: DIY Thermal LPM for under \$50

Quote:
 Originally Posted by MarioMaster There are a few options, you could use two wall warts (or a PSU with +/- voltage outputs) The other option is to use an isolated switching converter, but these tend to be noisy and require extra filtering components. There are also charge pump type chips that will also do this. You can use the isolated output and ground the positive output (9v2+), making the negative output negative to ground. That will be your 9v2-
I'll look into that. I know that the DMM will require a separate vcc in, so I'm trying to find circuits that will take a wall wart of some voltage/amperage output and putting out +9v, -9v, +9v. Proving to be difficult, but will really make for a neat package that doesn't depend on batteries if I can figure it out.
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01-13-2016, 03:05 AM #569
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Hibro
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Re: DIY Thermal LPM for under \$50

I have built this circuit but cannot get it work properly. Can someone please suggest a possible solution to this?

DIY LPM Not working properly. Need help finding problem.

Thanks

05-16-2017, 07:14 AM #570
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DutchLaser
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Re: DIY Thermal LPM for under \$50

Huge bump.

I am back from gone and want to make this LPM.
I do have al the components.
But now the V2.0 schematic (post#541) from Mariomaster is gone!

Who has it? Mariomaster hasnt been online for a long time.
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Last edited by DutchLaser; 05-16-2017 at 07:30 AM.

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