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My New LPM Design

brianpe

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Dec 26, 2012
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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!





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


Enjoy!
 



Snecho

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Oct 2, 2019
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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.
 

brianpe

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Dec 26, 2012
Messages
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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

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Dec 26, 2012
Messages
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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

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Feb 23, 2020
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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
 




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