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  • Author Author: kmikemoo
  • Date Created: 1 Jun 2020 10:48 PM Date Created
  • Views 2032 views
  • Likes 10 likes
  • Comments 8 comments
  • rpi4
  • raspberry pi
  • current clamps
  • datalogger
  • pico technologies
  • picolog
Related
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PicoLog CM3 Data Logger with RPi4 Hotspot

kmikemoo
kmikemoo
1 Jun 2020

This is a followup to my road test review.  While doing some of the tests that I proposed in my road test application, I thought of a few others.  This was the one that jumped to the top of the list.

The application is monitoring a building's current draw, both quantity and characteristics - such as large motor inrush demands caused by overhead cranes, etc.  Sometimes this type of survey is used to determine the size of a backup generator.  Sometimes it is used to determine if other loads can be added to an existing backup generator.  Electricians use it to chase electrical problems.  Is the issue intermittent or does it have a pattern?  All cool stuff.

 

When we do this with power meters, we make all the connections, close up the electrical panels as best we can and place the power meter where we can and leave.  We come back at a later date, save the data, recover the system and leave.

Wouldn't it be helpful to see what's going on while it's going on?  To get an indication of where the data might be leading us?

It's also nice to know that the system is working correctly once everything is buttoned up.  Sometimes an accidental button push costs you another week or month of logging.

 

The PicoLog CM3 AC Current Data Logger has network capabilities, either as a monitoring node on a network when using the Windows PicoLog 6 software or through a computer on the network (Windows, Mac, Linux or RPi).

But what happens when you're a service technician and the customer doesn't want you on their network?          I know.  I am crazy to suggest such a thing, but it does happen.

I guess we need to create our own network.

 

Of course, the Raspberry Pi 4 is perfectly suited for this application.  The only hotspot application that I know of is autohotspotN.  Most importantly, it works.

For those that want to install it the long way, https://www.raspberryconnect.com/projects/65-raspberrypi-hotspot-accesspoints/157-raspberry-pi-auto-wifi-hotspot-switch-…

For those that would like a simple method, Jason, KM4ACK, has a script.  https://www.youtube.com/watch?v=qMT-0mz1lkI&t=18s

 

To insure that my RPi4 used its own hotspot all the time, I removed all of the known networks from wpa_supplicant.conf.

Because not everything goes as planned, the IP of the hotspot is 10.10.10.10.  When wirelessly connected to the hotspot with a laptop, I used PuTTY to log into the RPi4 and start the VNC server.  From there, I was able to use RealVNC to launch and run the PicoLog 6 software.

 

I think I'll install this on the electrical service at my training center.  Let's get started...

Starting point.  Those are compact fluorescent lights on the left panel.  I really need to do better housekeeping.  Remove panel face.  Add current clamps.

imageimage

 

The RPi4 is going to need power.  Fortunately, there is a spare breaker in the panel.  Add convenient plug.  Connect clamps and USB.  Place CM3 neatly in cabinet.

imageimage

 

I did choose to pop out one of the knockouts instead of trying to sneak the cables from beneath the cover.  Add cover.

imageimageimage

 

Turn on circuit breaker and power up the RPi4.  Go fetch laptop.  Join RPiHotspot - which I renamed PicoLogHotspot.  I'm still not having any luck auto-starting the VNC server.  It did for a while and now it doesn't.  So, PuTTY to the rescue.  SSH in.  Launch vncserver.  Log in with RealVNC.  Launch PicoLog 6.

imageimageimage

 

Here's what the data log looks like after about an hour and over night.  I did have to go back and change the scaling on the current clamps when I first started, but I only lost 2 or 3 minutes of recording.

imageimage

I snapped this while sitting at my desk 30-ish meters from the panel.

The PicoLog CM3 AC Current Data Logger is quite versatile.  The average person wouldn't even notice the Raspberry Pi on the cabinet.  THIS is exciting stuff - at least to a generator nerd.

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Top Comments

  • fmilburn
    fmilburn over 5 years ago +3
    These are great posts Mike. I am enjoying reading theml.
  • kmikemoo
    kmikemoo over 5 years ago in reply to fmilburn +2
    fmilburn Thank you. I appreciate the feedback.
  • DAB
    DAB over 5 years ago +2
    Nice update. I have been impressed with the devices and software from Pico devices. DAB
  • three-phase
    three-phase over 5 years ago in reply to kmikemoo

    They are the two ways that I would know of to do this kmikemoo. If you have the transformers available then I guess that is the easiest option.

     

    The second option would probably be my preference, adding in a ptc and some varistors to provide a little protection. It would probably be possible to make up a little extension box with 4mm connectors and the 25 pin D-Type for connection to the PicoLog. That would seem like a nice tidy solution to me.

     

    I would have to go back to my unit to look at AC measurement as I have only every logged DC voltages from it and am unsure how it would respond to AC. There may be something on the Pico forums to look at as well and their engineers are usually pretty good with responding to questions.

     

    Kind regards

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  • kmikemoo
    kmikemoo over 5 years ago in reply to three-phase

    three-phase So the 2.5V limit is a bit intimidating.  And, that's Vpeak, not VRMS. I have two way to attack this.  The first would be with some control power transformers that I've rescued from the bin.  480V to 12.6V.  Then (stealing a page from cheap multimeters) run it through a rectifying diode to a voltage divider.  Adding a small capacitor to the circuit should give me a fairly consistent equivalent output voltage.  I can use the PicoLog 6 software to scale the circuit and get the readings I'm looking for..

     

    The other option is system voltage straight into a voltage divider as is done on many controllers.  I would still need the rectifier.  I would also use the filter capacitor unless the PicoLog has a function to convert this input into its RMS equivalent.  I haven't researched that part.  I would want to do this on a separate board to insure that I got it right before smoking a piece of test equipment.  That's the challenge of working with mains voltages, right?

     

    Those are my thoughts on how to do it.  I'm always interested if there's a better way.  It's one of the reasons I'm in this community. imageimage

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  • three-phase
    three-phase over 5 years ago in reply to kmikemoo

    Yes kmikemoo, once a RoadTest is started, it can be very easy to put your foot down for a long journey.

     

    I am the opposite to you, I have a 1216 PicoLog but not the CM3. Would need some thought about the voltage input into it and protection requirements though.

     

    Kind regards.

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  • kmikemoo
    kmikemoo over 5 years ago in reply to three-phase

    three-phase I have wondered the same thing.  I was very tempted to pick up a PicoLog 1012 to use with it, but decided to hold off.  I didn't want to get overloaded (distracted) with "project creep". 

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  • three-phase
    three-phase over 5 years ago

    Great addition to your RoadTest. I wonder how good an alternative one of these would be with a voltage logger to create a more sophisticated energy monitoring setup against a purpose built unit.

     

    Kind regards

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