My New LPM Design

[brianpe]

Several years ago I built an LPM based on an Ophir head, voltmeter, and DC-DC converter (original post). Since that time I've found the need for something new:

• Powers are getting higher, and my Ophir head maxes out at about 10 watts. Need a new head for dual-diode designs.
• Really large case takes up a lot of room in my toolbox.
• Separate sensor and cabling also takes up a lot of room in my toolbox.
• I would like it to be rechargeable.

I won an auction on E-Bay for a used Ophir head that can read up to 150 watts, so I rebuilt a new LPM board to work with it.

Features:

• Small, one piece unit (I do realize this compromises some utility and opens up the display for "attack" by a rogue beam, but it is a convenient form factor for me).
• Rechargeable LiPo via USB-C.
• My own voltmeter design now using 24 bit ADC. Auto ranging between mw and W.
• Max / Average and onboard logging.
• Auto power off...and off is really off so I can leave this in a drawer for a while without it losing charge.

While this looks like a two piece design, the sensor is screwed to the display. I originally had a one piece design but It was very thick and resembled an early cell phone. This looks a little more streamlined to me. I looked into some sweet magnetic connector so I could swap out sensors...but decided I just needed to call it done. This was a pretty long project.

Photos!

PC Board Back

• brianpe
• Apr 5, 2020

PCB, back side

PC Board Front

• brianpe
• Apr 5, 2020

PCB, front side

Action Shot

• brianpe
• Apr 5, 2020

LPM measuring power. Graph at the bottom shows trend

Logging Viewer

• brianpe
• Apr 5, 2020

Logging view, showing log as a graph

I've published the Eagle files, firmware source and case IGES files to this GitHub repo:

GitHub - brianpepin/lpm: Design for a laser power meter using Ophir's analog sensors

Design for a laser power meter using Ophir's analog sensors - brianpepin/lpm

github.com

Enjoy!

 

[Snecho]

That has got to be the coolist thing I've seen in a while! You designed that yourself? Wow. This is a truly amazing accomplishment, congrats

You should sell these.

 

[gazer101]

How much did the parts cost you ?

 

[brianpe]

That has got to be the coolist thing I've seen in a while! You designed that yourself? Wow. This is a truly amazing accomplishment, congrats

You should sell these.

Happy to leave that market to J Bauer. It would drive me nuts if I *had* to make these.

 

[brianpe]

How much did the parts cost you ?

Do I have to admit that?

The Ophir sensor was $277 and the most expensive single part. Electronic components were about $150 with $60 of that just the display. Then there was PCB fabrication (~$50), 3D printing ($40) and, I'm a little ashamed to say, the grey front panel was a custom graphic overlay the would have been super cheap in quantity....but turned out to be $180 to have a single one made. The thing just didn't look finished without it though. I got a little carried away but after a while it was kind of a test to see how professional looking I could make it. It could have been done a lot cheaper.

 

[gazer101]

Do I have to admit that?

The Ophir sensor was $277 and the most expensive single part. Electronic components were about $150 with $60 of that just the display. Then there was PCB fabrication (~$50), 3D printing ($40) and, I'm a little ashamed to say, the grey front panel was a custom graphic overlay the would have been super cheap in quantity....but turned out to be $180 to have a single one made. The thing just didn't look finished without it though. I got a little carried away but after a while it was kind of a test to see how professional looking I could make it. It could have been done a lot cheaper.

That's an amazing price! Hats off to you

 

[lasersbee]

Just saw this Thread...
Well done for a DIY LPM...
Looks very professional Brian.

Jerry