DIY Laser Power Meter

[toked323]

here it is knimrod will it work?
http://www.mcminone.com/product.asp?product_id=72-8100&catalog_name=MCMProducts

 

[knimrod]

hey knimrod i may be in for one, i found lcd's for 4$ ill send you the link so you can tell me if it works?

$4.? Wow! I'll take a look, sure.

 

[toked323]

heres the link they raised the pice to 6$
http://www.mcminone.com/product.asp?product_id=72-8100&catalog_name=MCMProducts

 

[knimrod]

2 potential problems I can see... The input is rated at 199mV full scale. We want 1999mV full scale. You would need to either install a couple resistors in the DPM as a voltage divider, or change a few resistors in the amp circuit to get a different gain. Lastly, there is nothing in the specs or datasheet that indicate whether or not the voltage being measured and the power supply can share a common ground. Many DPMs cannot do this and it's a question that would have to be answered by the supplier or manufacturer.

 

[toked323]

ok gotcha

 

[toked323]

hey knimrod, is it possible to just take out the panel meter out of my multimeter

 

[knimrod]

hey knimrod, is it possible to just take out the panel meter out of my multimeter

Anything's possible I suppose but I sincerely doubt that it's at all practical.

 

[amkdeath]

[quote author=chimo link=1200112201/210#221 date=1203168305]
doh! I forgot about the one(s) that come on the board.  Are they soldered in or socketed?  Oh I just noticed that you have me down for 3, I actually meant teh 3rd group buy (batch 3) but you can keep me down for 2.

Ooops..  Okay, 2 then..

The LTC1050s on the Coherent board are soldered but fairly easy to remove just the same.  I have a fancy desoldering tool but I suspect a heat gun will do the trick too.
[/quote]

I use a jet lighter torch (liek the 2000C triple flame lighters on DX) and I heat the back while pulling on the chip. I have also removed about all the resistors on the board, LOL theres liek nothing left on it...

 

[Zarniwoop]

I used a 200mV panel meter, but added a switch and a voltage-divider so I could get 0-199.0 mW, or 0-1.999 Watts. Since most of what I'm measuring is <200mW, I like having the fractional digit available.
(At least that was the plan - in practice, there's enough thermal fluctuation to make that 1/10mW a moot point.)
I also swapped the 10K zero-offset pot for a 5K with a fixed 2.2K resistor on each leg - it was awfully touchy the original way.
The panel meter I got allows for common-ground if you use their suggested resistor-network hookup, but I just went for simplicity, and put in a 3rd battery. There was room in the case, and a non-backlit DPM draws so little current, I may never have to change the battery.

For a voltage divider, I used a 100K 25-turn pot and a 750K resistor, then calibrated it for a 10:1 drop.
Easier than finding precision resistors of exactly the right values.

 

[amkdeath]

I BUILT MY LPM TODAY!!!

YAY

I got the oarts in the mail, still waiting on the DPM tho. Im using a DMM for now. this did help me realize that my Senkat laser's batteries needed to be changed (it was reading 75mW!!) after I changed batts, I got 140mW fro my senkat laser. My open can MXDL is going through Open heart surgery right now, I almost killed the diode on that, and the guts have fallen apart, Ill have to fix it after im done posting this.

I must say, after my mom, the sensor and the 10K zero pot are 2 of the most sensitive things on earth!! a little touh and my zero screws over, and if my hand is 5 in. from the sensor head, it picks up the heat!!!

overall great and EASY build, im glad i didnt go for a lasercheck, or an insanely expensive coherent LPM....

regards,

amk

 

[knimrod]

Let me say this about the zero pot.. If you really need it to be less sensitive, you can increase the value of R5.. It's not critical, more resistance will be less sensitivity. However, if your using a DMM and can see the digit that represents 1/10 of milliwatt, the zero adjust will be about impossible. Set the DMM to the 2 volt range, not the millivolt range. It will make zeroing and measuring much easier.

 

[amkdeath]

Let me say this about the zero pot..  If you really need it to be less sensitive, you can increase the value of R5.. It's not critical, more resistance will be less sensitivity.  However, if your using a DMM and can see the digit that represents 1/10 of milliwatt, the zero adjust will be about impossible.  Set the DMM to the 2 volt range, not the millivolt range.  It will make zeroing and measuring much easier.

well, I know this it OT, but I just killed my open can, it works, but the negative lead fell off the diode... I dont knwo how to fix it....

regards,

amk

BTW, I did have it at the mV range, maybe thats why

 

[amkdeath]

well, the other lead fell off my open can too. I guess it can go in the "Dead" category now...

regards,

amk

 

[TheMonk]

[quote author=TheMonk link=1200112201/195#199 date=1203043224]Knimrod,

I got the thermo senor + board no DPM yet.
How do I power up the sensor and use my MultiMeter (2v with 1mV increment, 1mV=1mW) to measure Laser power?

thanks
TheMonk

Why not just build the board up and use your multimeter with the amp board until our DPM arrives?[/quote]
Knimrod,
I finish building my board and calibrated VR1 (less the LED and VR2 and no DPM), how many 9v batteries do I connect to the board now for testing using my Multimeter?

regards
TheMonk

 

[knimrod]

[quote author=knimrod link=1200112201/195#207 date=1203050801][quote author=TheMonk link=1200112201/195#199 date=1203043224]Knimrod,

I got the thermo senor + board no DPM yet.
How do I power up the sensor and use my MultiMeter (2v with 1mV increment, 1mV=1mW) to measure Laser power?

thanks
TheMonk

Why not just build the board up and use your multimeter with the amp board until our DPM arrives?[/quote]
Knimrod,
I finish building my board and calibrated VR1 (less the LED and VR2 and no DPM), how many 9v batteries do I connect to the board now for testing using my Multimeter?

regards
TheMonk[/quote]

The amp requires a bi-polar power supply so you'll need two 9V batteries.

 

[knimrod]

I've completed a preliminary design for a PC interface module and started a new thread here. If there's enough interest, I'll advance the project along..