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DIY Laser Power Meter

knimrod

knimrod

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TheMonk said:
I shorted the input I got 0.56v, then I re-connected the sensor head it started at 6.5v and went up to 8.2v again.
I disconnected the sensor head and shorted the input again, it went back to 8.2v. :-/
Click to expand...

The .56V output with a shorted input I can buy into if the offset control is at one end of the range. It doesn't make any sense that it wouldn't repeat however. Maybe a picture of the back of your PCB?
 





knimrod

knimrod

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I can't discern anything obviously wrong with your assembled PCB.. I suspect either a problem with your LTC1050, your sensor head/cable, or something unseen relating to the assembly.

The only other thing I can think for you to check is to measure the resistance of the sensor head output (disconnected from amp), with and without the cable. it should measure ~2.3K-2.5K. If it's infinite, there may be a problem there.

If you like, pack it up and send it to me. I'll fix it for ya.
 
TheMonk

TheMonk

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knimrod said:
I can't discern anything obviously wrong with your assembled PCB..  I suspect either a problem with your LTC1050, your sensor head/cable, or something unseen relating to the assembly.

The only other thing I can think for you to check is to measure the resistance of the sensor head output (disconnected from amp), with and without the cable.  it should measure ~2.3K-2.5K.  If it's infinite, there may be a problem there.

If you like, pack it up and send it to me.  I'll fix it for ya.
Click to expand...
My sensor head is OK it measured 2.28k.

Thanks for the offer to fix it. :D Amk is sending me a LTC1050, :D I will replace it first and see what happen. ;)

regards,
TheMonk
 
C

cybob101

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i wanna build this but i think i will need help, also how much will it cost to build?
 
knimrod

knimrod

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cybob101 said:
i wanna build this but i think i will need help, also how much will it cost to build?
Click to expand...

There's lots of people here to help you. The cost depends on how far you want to take it but I estimate the minimum to be about $50. for a version that displays power on a common multimeter.

There is only 1 PCB left in the current group buy however. You may want to claim it if you're planning on building one of these meters.
 
amkdeath

amkdeath

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cybob101 said:
i wanna build this but i think i will need help, also how much will it cost to build?
Click to expand...


I was skeptical at first, and trust me, its an EASY build.

I just got my meter today (DPM) and boy is it beautiful!!! it is WELL worth my money. I suggest that you also go for the meter, its more professional looking, and its just easier.

my new IR from TheMonk measures 165 avg. and 170 peak with glass AR coated lens

My Senkat diode (with a heavily damaged can window thanks to friend) with AR coated glass lens reads 130 avg and 145 peak.

I killed my MXDL open can running at 420mA just before I got this set up, so Ill have to wait for my replacement diode (from TheMonk) before I can give an estimate for that.

I have been needing an LPM for a while, I was considering a coherent lasercheck, but thats 500 bucks!! almost all LPM's i found were expensive, and I could not ind a decent DIY one. this was awesome, the cheapest and most cost efficient / easy DIY LPM i have ever seen.

you cant go wrong, try it!
 
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toked323

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im still thinking knimrod if i can get a cheaper display then i will buy one from you
 
knimrod

knimrod

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I just got the blue back-lit DPM from "New2006Power".  It's a very nice blue color display and it doesn't have the white 'V' in the lower right corner.  It also doesn't have the screen like textured background of the green display.  I like it!
 

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amkdeath

amkdeath

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well, I just brought my MXDL back to life again

(funny, story, the envelope showed up in my mailbox all smashed, like it went through some kind of garbage compactor... it was in a sealed plastic bag from USPS saying "We care" and "sorry for the damaged mail". TheMonk's superior packaging of the open can that was in that evelope protected it, and even though the package looked like it was used to play volleyball, the open can (that was NOT in a module) came out untouched!)

anyhow, I maesured it, and it only shows 160 on the LPM!!! all my other lasers are showing under spec on there too... What is wrong? coult it be from weak batteries? the 9v's I attatched were preety used and weak...


regards,

amk
 
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LarryQ

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Ummmm

Under spec from what other power meter?

Were you just "Estimating" the output from a metered Current/Voltage?

Unless your batteries are low in your laser....and IF you set your gain per the Formulae Knimrod gave...then you are reading the real power of your Laser...


I have found this meter's design to be extremely accurate, If built and set properly......

Besides..160mW sounds pretty good for a Harvest Diode without cooling considerations!!



Larry
 
knimrod

knimrod

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amkdeath said:
well, I just brought my MXDL back to life again...
anyhow, I maesured it, and it only shows 160 on the LPM!!! all my other lasers are showing under spec on there too... What is wrong? coult it be from weak batteries? the 9v's I attatched were preety used and weak...
Click to expand...

What power were you expecting? I doubt it's the 9V batteries.. They would have to be pretty low before you would see any effect. Did you measure their voltage? Assuming you're expecting ~260mW, 160mW is way off (~40%). How far off do you estimate all your other lasers are measuring? I don't think you could calibrate it that far off with your gain pot if you tried. Are you sure all your resistor values are correct?
 
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toked323

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hey knimod, if you didnt send this out yet, if you have any extra parts for this like resistors and diodes, and you want to sell , well do you want to? and weres the schematic to build this?
thanks, Toked
 
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