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DIY Thermal LPM for under $50

Benm

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The better way i heard can be black anodization, but as far as i know, is virtually impossible to obtain on a non-metallic surface ..... wondering if the anodization process can be made on the side of a TEC with gold plated layer, without destroy the TEC or the gold coating ..... maybe a low current process keeping the TEC plate with only the gold layer in contact with the surface of the liquid ..... can require a complicate setup, anyway .....
Anodization only works on a very select set of metals, aluminium being best known since its anodized more often than not in many applications.

The anodization process results in a certain color depending on layer thickness, and the layer can be transparant for visible light. It is however possible, and often done, to include a dye in the anodized layer giving it a black (or some other) color.

As far as paint goes: something intended to radiate heat well might be suitable, this could be paint for exhaust systems, or, for example black radiator paint. I'm sure there are blacker materials available, but not easy to apply or obtain. Carbon black pigment springs to mind, but i doubt that would tolerate higher power densities very well.
 



TTerbo

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whats the max viltage input for one of those? i found a 10mm by 10mm on but it tais max voltage 0.81?
and could i just paint a 10mm by 10mm square on the 40 by 10mm?
cheers
 

MarioMaster

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It depends on the TEC, and no you can't just paint a small surface of a large tec - the problem is that larger tecs have a larger thermal resistance and heat capacity and thus take much longer to react to a laser. Also when the junctions are smaller it allows the laser energy to hit more junctions at once, resulting in a higher output voltage.
 

TTerbo

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sorry i worded that bad, i meant what rec should i get what is the max voltage or lowest voltage the tec needs for this circuit?
cheers
 

lasersbee

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It depends on the TEC, and no you can't just paint a small surface of a large tec - the problem is that larger tecs have a larger thermal resistance and heat capacity and thus take much longer to react to a laser. Also when the junctions are smaller it allows the laser energy to hit more junctions at once, resulting in a higher output voltage.
Sorry to disagree with you MM.... not true.... a 100mW laser whether collimated
to 1mm diameter or 10mm diameter... will still give the same output voltage on
a WaferType Thermopile like a TEC used in the Seebeck Effect mode...:cool:


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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MarioMaster

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Yes it will still scale properly but im talking about the overall output voltage of a tec with a higher junction count due to smaller junction size.

If the output of the TEC is larger to begin with you need less gain from the op-amp and thus less noise and error possibilities.
 

MarioMaster

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basically higher input voltage is better, because for a higher input voltage you need more junctions. I wouldn't recommend going much larger than 15x15mm
 

TTerbo

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kool. i found a 10 by 10mm with max voltage of 2.3??
 

TTerbo

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ok guys you are going to find this stupid but.
Positive rep for the person that finds a way for me to use a 40 by 40mm pelter tec My pop has one.
i have heatsinks etc please :)
cheers guys
 

lasersbee

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You can use the 40mm X 40mm TEC....
But your settling time will be long...

@MM.... I agree that between different TECs the more junctions
one has over the other... the higher the Voltage for the same
thermal identical input.. that is not taking into account the ceramic
plate mass and dissipation variations...:cool:


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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Bionic-Badger

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I'm trying to build something reproducible, using a specific filament lamp and lenses that can be found easily (still works in progress, sorry) ..... anyway, the principle is the following one: if i get a lamp type that can be found almost all around the world (as example, car lamps, that are more or less standardized both in production and distribution), and focus the filament image on a certain dimension on the reading plate, with a precise voltage, i can build, probably, a decent thermal calibration system that is independent from the plates and paint layers .....
Can't you put a known power resistor in a reflective container and measure the heat it gives off on the sensor? Ideally, the power used by the resistor is all converted into heat.
 

Prototype

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That's more or less how they calibrate meters professionally, they use a 1W resistor and adjust the sensor until it's reading 1W from the heat. That's how Jerry calibrates his meters, you can see it on his site in one of the pictures, the resistor is in a TO-3 butterfly package. Or at least, that's what I was told, and this is obviously my simplified version of the story.
 

HIMNL9

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Can't you put a known power resistor in a reflective container and measure the heat it gives off on the sensor? Ideally, the power used by the resistor is all converted into heat.
Yes, but this present a problem ..... not all the surfaces adsorb or reflect the same way, or linearly .....

Doing this, the emission is entirely in the very far infrareds (heat), and require specific setups, that i doubt can be reproduced easily (how much hobbysts can build a calibration chamber ?) ..... where instead we need some reliable system for calibrate sensors in the visible light spectrum part, mainly ..... if we reach to produce a stable and efficent setup that only require a known type of lamp and some common lenses, is not this better ?


EDIT: the idea of the resistor is not totally to discard, but only if the resistor is part of the reading head, and if we know the reflective factor of the head ..... i mean, if you know that your reading head surface have a linear reflection index of, say, 10% on all the light band, then you may glue a resistor on the back of your head, and send to it, as example, 90mW of energy, calibrating the instrument for a reading of 100 (90 plus the 10% that the reading surface always reflect away) ..... but the resistor must be part of the thermal mass of the head, too, for precision (anyway, actually is possible made "printed" resistors with a thermal mass so small that is practically ininfluent ..... i think some serie from Scientech also uses this system, having a thermal calibration element built-in in the heads)
 
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TTerbo

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thanks lasersbee. i cant rep you yet :( although if i added a cap in paralell with the thermo pile would this charge up then release the voltage and give a quicker reading
 

MarioMaster

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thanks lasersbee. i cant rep you yet :( although if i added a cap in paralell with the thermo pile would this charge up then release the voltage and give a quicker reading
No, in fact it would only serve to reduce the reaction time of the sensor. There is already a 0.1uF capacitor across the TEC but that is just to filter noise and voltage transients.
 




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