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DIY Thermal LPM for under $50

MarioMaster

MarioMaster

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I think those might be too small - again try to find the one with the most junctions yet is fairly small. Usually voltage is tied to junction count.
 





Xplorer877

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Cool sounds good.

BTY what's the differance between TECs and thermopiles? I sent Jerry a PM asking if he had any spare thermopiles. Would those be suitable?

-Tony
 
HIMNL9

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Xplorer877 said:
Cool sounds good.

BTY what's the differance between TECs and thermopiles? I sent Jerry a PM asking if he had any spare thermopiles. Would those be suitable?

-Tony
Click to expand...

A TEC is a thermoelectric "heat pump" that take the heat from one side and carry it to the other (producing in the process more heat on the "hot" face), made with a lot of silicon junctions connected in serie ..... when you use it "in reverse", for a phisical factor called "seebeck effect", the junctions produces some current when there is a difference of heat from the two sides, and more is the difference, more is the output voltage ..... we use them "in reverse" for make homemade or experimentals LPMs .....

The thermopile is a joint between 2 different metals, that produce current when heated directly, and a "thermopile" measuring head is, normally, made with a disk of adsorbing material, joined with a lot of thermopiles junctions in the back part, all in series, so the output voltage is increased .....

This second element is specifically made for thermal / radiant energy detection, so is, ofcourse, much more efficent and sensitive than a TEC used in reverse, but at the same time, is also much more high cost .....

The laserbee (i suppose that you are referring about that) uses a very good TEC element, maybe not sensitive as a real thermopile, but enough for detect also few mW of power ..... as example, all the TECs that i have around, except maybe the 6x6mm ones, are not sensitive as the one that he use in his product ..... (but i cannot judge the products that can be found in other countries, based on the ones that i can find here ..... here in Italy the distribution system is so crap, that sometimes i have difficults in finding the 40x40mm ones :p)
 
TTerbo

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in that schematic why isnt R1 conected to anything else? and why are only 2 leads connected on the Pots?
 
Xplorer877

Xplorer877

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HIMNL9 said:
A TEC is a thermoelectric "heat pump" that take the heat from one side and carry it to the other (producing in the process more heat on the "hot" face), made with a lot of silicon junctions connected in serie ..... when you use it "in reverse", for a phisical factor called "seebeck effect", the junctions produces some current when there is a difference of heat from the two sides, and more is the difference, more is the output voltage ..... we use them "in reverse" for make homemade or experimentals LPMs .....

The thermopile is a joint between 2 different metals, that produce current when heated directly, and a "thermopile" measuring head is, normally, made with a disk of adsorbing material, joined with a lot of thermopiles junctions in the back part, all in series, so the output voltage is increased .....

This second element is specifically made for thermal / radiant energy detection, so is, ofcourse, much more efficent and sensitive than a TEC used in reverse, but at the same time, is also much more high cost .....

The laserbee (i suppose that you are referring about that) uses a very good TEC element, maybe not sensitive as a real thermopile, but enough for detect also few mW of power ..... as example, all the TECs that i have around, except maybe the 6x6mm ones, are not sensitive as the one that he use in his product ..... (but i cannot judge the products that can be found in other countries, based on the ones that i can find here ..... here in Italy the distribution system is so crap, that sometimes i have difficults in finding the 40x40mm ones :p)
Click to expand...

That makes sense. Thanks for the reply.

-Tony
 
Meatball

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Quick Parts check:

I have a 10mm X 10mm TEC,

and I have one 741 Op amp package.

This won't mess with the resistance values... correct?

Thanks,

-Tyler
 
HIMNL9

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Meatball said:
Quick Parts check:
I have a 10mm X 10mm TEC,
and I have one 741 Op amp package.
This won't mess with the resistance values... correct?
Thanks,
-Tyler
Click to expand...

Sorry, in what sense ?

Also, 741 require a double power supply, if you want to use it in a stable and good configuration ..... and is a single op-amp, so the pins are different .....
 
Xplorer877

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I'm still not really sure what TEC to get. I think that 15x15mm is too big. Even if it does have a high number of junctions the laser beam will concentrate it's power to a smaller localized number of junctions. I know that the ceramic plate is meant to distribute the heat but wouldn't it be better to just buy one that has more junctions per sq cm, like this:

03111-9J30-20CA

This one is less than a sq cm yet is has about 8 little elements per side. Yeah it's expensive but if it's more sensitive then to me it'll be worth it. The area of the laser beam will "hit" more of those junctions directly. Since they're wired in series, naturally the more of them that are stimulated the more voltage they will produce. What do you think?

-Tony
 
Last edited:
MarioMaster

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That one will probably work fine.

The laserbee uses an 8x8mm TEC to give perspective.

I used a 1cmx1cm TEC from a dead TO-3 laser diode for my testing and it was quite sensitive although the readings did take a few seconds to stabilize. It also still had a pretty good glob of indium on the surface that used to be soldered to the laser diode.
 
Meatball

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HIMNL9 said:
Sorry, in what sense ?

Also, 741 require a double power supply, if you want to use it in a stable and good configuration ..... and is a single op-amp, so the pins are different .....
Click to expand...

Yes, I figured the pinout would be different, but I was simply hoping to compare the pins and then remake the schematic using the 741. Its the only op amp available in my area. If It needs a double power supply, I can give it that. I was just hoping that the resistor values would not be greatly affected.

Maybe a quad op amp would be useful...

-Tyler
 
Last edited:
TTerbo

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BUMP

Im nearly done mine..with the help of eudaimonium. shall post here if it works :p
 
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