Fun way to monitor DC current

XRingerXRinger Solar Expert Posts: 529 ✭✭✭
(non-contact), up to 400 amps.. And display the data on your PC.

Check out my new toy. A CAI webcontroller board. (See link below).
It has three 0 to 10vdc analog inputs that should work with the cheap Hall Effect
current sensors I found on Ebay.


http://ecorenovator.org/forum/appliances-gadgets/1871-webcontrol-universal-industrial-controller.html

The board can also be used with a cheap X10 transmitter (Firecracker),
to control any X10 modules you might own.

It also has the firmware to read up to 8 of the DS18B20 1-wire temperature sensors.
(And one Honeywell HIH-4000-001 Relative Humidity Sensor)..

My plan is to try using two of the current sensors (on 2 of the 3 analog inputs)
to monitor the AC power use of my two Sanyo Mini-split ASHPs.

Cheers,
Rich

Comments

  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Fun way to monitor DC current

    Nice progress, and interesting to read.

    You might be able to save a bunch of time if you want a little bit less of a DIY project. Take a look at this product:
    http://www.welserver.com/intro.htm .

    An example of using it for things you're doing is here:
    http://www.welserver.com/WEL0043/
    In my case I'm measuring solar PV power, but have been looking at DC current sensors since I do have 2 analog 0-10 VDC channels available.

    Lastly, here's an interesting summary of a lot of examples of what you're doing:
    http://www.welserver.com/index.htm

    Best regards,

    Bill
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Fun way to monitor DC current

    I forgot to mention that you might want to consider
    http://www.hobby-boards.com/catalog/product_info.php?cPath=22&products_id=46 for humidity measurement. It's a 1-wire device so it can conveniently connect to your 1-wire network that you've already built for your temp sensors. This product comes in two versions, one with a conformal coating that makes is weather resistant for outside applications.

    I've been using two of these (one for outside, the other for inside) since 2007, with no known problems. While more expensive than the raw Honeywell RH sensors, this product makes it easy to interface to the sensor via the universal 1-wire bus.

    Best regards,

    Bill
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Fun way to monitor DC current

    Wow! When I saw "The minimal WEL in a Box (above) is ideal for a DIY'er, and costs $395. & WEL Starter Kit (right) is ready to run out-of-the-box with 10 temperature sensors and costs $555. "

    I was a little startled.. The CAI board was $38 shipped & those DS18B20 Temperature Sensors are $1 each on Ebay..


    I figured I paid a lot ($18 shipped) for the Honeywell HIH-4000-001 Relative Humidity Sensor,
    but that $54.50 Humidity board is making me feel good about buying the Honeywell!


    That logging software looks neat.. But, I'm not really into keeping a lot of records,
    but controlling things in real-time. Plus, being alerted to problems as they come up.

    The reason I posted here, is because I know PV folks love clamp type amp meters,
    and a few of these $9 Hall sensors http://www.ebay.com/itm/200665382364?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
    used with the CAI board is a fairly inexpensive project for the DIYer..

    Cheers,
    Rich
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Fun way to monitor DC current

    Thanks for the comments. I wish I had DIY skills at the level you do. I could save a lot of money. And I'd probably learn a lot more too.

    If you happen to come across an off-the-shelf device that measures DC current up to at least 25 A Full Scale with either a 4-20 ma or a 0-10 VDC output, I'd sure appreciate a note or comment. My monitoring board has two analog channels, and I'd like to use one of the channels to look at my solar system's current output as a function of time of day and some shading considerations. My system's current output ranges from 0 - 22 A DC.

    And additionally, if you happen to come across an off-the-shelf device that measure DC voltage up to at least 450 V Full Scale with either a 4-20 ma or a 0-10 VDC output, I'd again appreciate a note or comment. This would allow me to look at my solar PV system's voltage output as a function of time of day. My system's voltage can go as high as 448 VDC open circuit.

    CR Magnetics manufactures a device that meets the needs noted above. But, they're expensive, at over $200 each, plus the need for a 24 VDC power supply.

    The objective is to get to something like this:

    large.jpg


    Many thanks!

    Best regards,

    Bill
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Fun way to monitor DC current

    Seems like it would be pretty simple to make a voltage divider to allow
    a 5 or 10vdc analog input to measure 450volts as 4.5volts.
    Displaying it with PLC is as easy as MUL AIP1 100 VAR1 Not really rocket science.
    Best to use a nice 10 turn pot to get it adjusted just right.

    Measuring 22A of current would be a little harder. But could be done with:
    1. controller board with a 5 or 10v range analog input.
    2. $9 Ebay Hall Effect current sensor.
    3. $6 Ebay 12vdc regulated power supply (wall wart).


    One could likely get nice looking plots using Excel to import the data from
    a CAI board, but I'd have get an Excel expert to show me how to
    refresh the data imports regularly, using the PC's RTC.

    I got power use plots with my TED. I looked at them a couple of times,
    then got bored with them. It seems like much of the software is a bit crude.
    I wasted my money on that TED 'footprints' software.
    The coolness factor wore off in about 20 minutes.. :roll:
  • a0128958a0128958 Solar Expert Posts: 316 ✭✭✭
    Re: Fun way to monitor DC current
    XRinger wrote: »
    ... make a voltage divider to allow
    a 5 or 10vdc analog input to measure 450volts as 4.5volts...

    ... Measuring 22A of current would be a little harder. But could be done with:
    1. controller board with a 5 or 10v range analog input.
    2. $9 Ebay Hall Effect current sensor.
    3. $6 Ebay 12vdc regulated power supply (wall wart).

    Thank you.

    WRT 450 VDC voltage measurement: While designing a voltage divider is very much within my DIY skills, I'd be uncomfortable not having good isolation between the solar system power and the control signal power. My monitoring system is connected to my LAN which is connected to a number of workstation PCs. I'm going to keep looking for an off-the-shelf product that offers isolation.

    WRT 22A of current measurement, this looks doable within my DIY skills as you suggest above. Isolation is fine becuase of the physical separation. I already have items 1 and 3. I'll keep on the look out for a suitable Hall Effect current sensor.

    Best regards,

    Bill
  • XRingerXRinger Solar Expert Posts: 529 ✭✭✭
    Re: Fun way to monitor DC current

    The Ebay current sensor I referenced above http://www.ebay.com/itm/200665382364

    Can measure your Amps.. Just need to borrow a DC amp clamp-on meter to calibrate the output signal voltage.
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