Old 11-09-2014, 10:21 PM #1
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Default Cheap LPM's, is that a TEC used on the head?

For the less expensive laser power meters, is that a thermal electric cooler used in reverse to generate a small amount of voltage I see mounted on the power heads? If so, I should be able to just use a cheap TEC from ebay, paint it black with the right material and then measure the voltage the heat produces at a given ambient temperature and compare with a chart to get the laser power output, right?

Couldn't a seller make a calibrated chart for individual TEC's and just sell those instead of buying a whole unit to convert the voltage to milliwatts etc? Many of us already have volt meters.


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Divergence to spot size calc: - 1 mRad is about .057 degrees which expands to be very roughly ~10% the diameter of the moon or sun at their distances.

Divergence Calculator: pseudonomen137's JScript mRad Calculator - Measure your lasers beam dia. at 1 foot & then 20'.

Online calc. to determine spot intensity at different mRad's & powers: http://tinyurl.com/divergence-calculator

Laser Power Density Calculator: Laser Power Density Calculator - Ophir

Build a beam expander to reduce divergence: http://tinyurl.com/BeamExpander

University YAG Project The Professor's Homebuilt Lasers Site - YAG Lasers

YAG Power Calc. Laser Peak Power Calculator - Ophir

Angular Size Calculator; use with diode angle of radiation spec. for lens dia. at FL: Angular Size Calculator

RHD's Calc: http://lsrtools.1apps.com/RelativeBr...&useRaleigh=on

High Current Pulse Drivers: https://tinyurl.com/ya7whuk3

Last edited by Alaskan; 11-09-2014 at 10:24 PM.
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Old 11-09-2014, 10:42 PM #2
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Default Re: Cheap LPM's, is that a TEC used on the head?

sure is, but every TEC is different so they would have to be calibrated individually. If I could buy a calibrated TEC I would totally build a megacheap arduino based LPM.
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Old 11-10-2014, 12:03 AM #3
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Default Re: Cheap LPM's, is that a TEC used on the head?

Wish someone would sell calibrated TEC's, but I can see they would probably need to be mounted on a specific heatsink too, but maybe not.

I suppose I could just simply unplug the head from my laserbee and see what voltage is produced at a given power, as displayed on the unit and chart out something approximate. The heatsink on it is very generic too, this could be duplicated without much trouble except for making sure you have a good reference to know you are tracking accurately enough or not.
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Attention new brothers of the collimated light!

Newbie advice: Please take the time to first make an introduction in the Welcome section before posting questions.


Divergence to spot size calc: - 1 mRad is about .057 degrees which expands to be very roughly ~10% the diameter of the moon or sun at their distances.

Divergence Calculator: pseudonomen137's JScript mRad Calculator - Measure your lasers beam dia. at 1 foot & then 20'.

Online calc. to determine spot intensity at different mRad's & powers: http://tinyurl.com/divergence-calculator

Laser Power Density Calculator: Laser Power Density Calculator - Ophir

Build a beam expander to reduce divergence: http://tinyurl.com/BeamExpander

University YAG Project The Professor's Homebuilt Lasers Site - YAG Lasers

YAG Power Calc. Laser Peak Power Calculator - Ophir

Angular Size Calculator; use with diode angle of radiation spec. for lens dia. at FL: Angular Size Calculator

RHD's Calc: http://lsrtools.1apps.com/RelativeBr...&useRaleigh=on

High Current Pulse Drivers: https://tinyurl.com/ya7whuk3
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Old 11-10-2014, 12:19 AM #4
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Default Re: Cheap LPM's, is that a TEC used on the head?

You are correct, they are just a TEC on a heatsink.



Here's why no one sells calibrated TEC heads:

The TEC, amplifier and coating all have pretty wide tolerances, so each unit needs to be individually calibrated.

Calibration is by far the longest and most annoying part in hobby LPM production, and accounts for majority of the cost when you buy one. If someone were to sell calibrated TEC heads it would be close to the price of the whole unit, minus the part cost for the micro controller + LCD, and the extra assembly time (which is not much).

On top of all that the market for just calibrated TEC heads is much smaller. Most people would prefer to buy the whole unit, and most people who want to DIY don't mind paying a bit more to have a dedicated display and micro controller rather than use a voltmeter.


Quote:
Originally Posted by Laser Project View Post
I suppose I could just simply unplug the head from my laserbee and see what voltage is produced at a given power, as displayed on the unit and chart out something approximate.
IIRC Trevor made a post about this, what he did was fed a millivolts at a time into the LPM input and created a voltage to power calibration chart from that.

Last edited by ARG; 11-10-2014 at 12:19 AM.
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Old 11-10-2014, 01:22 AM #5
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Default Re: Cheap LPM's, is that a TEC used on the head?

@LP: if you are looking to build one, check out this thread: http://laserpointerforums.com/f42/di...0-a-51129.html

Quote:
Originally Posted by ARG View Post
You are correct, they are just a TEC on a heatsink.

Here's why no one sells calibrated TEC heads:

The TEC, amplifier and coating all have pretty wide tolerances, so each unit needs to be individually calibrated.

Calibration is by far the longest and most annoying part in hobby LPM production, and accounts for majority of the cost when you buy one. If someone were to sell calibrated TEC heads it would be close to the price of the whole unit, minus the part cost for the micro controller + LCD, and the extra assembly time (which is not much).

On top of all that the market for just calibrated TEC heads is much smaller. Most people would prefer to buy the whole unit, and most people who want to DIY don't mind paying a bit more to have a dedicated display and micro controller rather than use a voltmeter.


IIRC Trevor made a post about this, what he did was fed a millivolts at a time into the LPM input and created a voltage to power calibration chart from that.
I wondered. I knew the radiant couldnt cost much to make, and I just assumed the rest of the price was due to calibration. Speaking of radiant, have you heard anything on the new meter?
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Old 11-10-2014, 02:28 AM #6
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Default Re: Cheap LPM's, is that a TEC used on the head?

Quote:
Originally Posted by crazyspaz View Post
I wondered. I knew the radiant couldnt cost much to make, and I just assumed the rest of the price was due to calibration. Speaking of radiant, have you heard anything on the new meter?
Just waiting on one supplier for a part last I heard
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Old 11-10-2014, 06:21 PM #7
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Default Re: Cheap LPM's, is that a TEC used on the head?

Oooh nice
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