Does anyone have any experience with this unit. My thought was to use it to monitor PV wattage via a 100a 75mv shunt on the lowside return of the combined PV array.
It monitors voltage fine but for the life of me I cannot get the current properly calibrated. I have tried introducing a variable mv source in place of the shunt. I do not frustrate easily, but here I am.
Am I missing something stupid?
Does it read zero amps with no load ?
How far is it off ?
Does it appear to have a gain that is too low or too high ?
Well, some new info. I was able to use my millivolt injector and achieve a decent calibration of the current.
zero @ zero 25a @ 18.75 mv 50a @ 37.5mv 100a @ 75mv.
However, when switched back to the shunt, there seems to be a negative offset. It was early morning and the battery bank was charging @ about 100watts but the signal arriving from the shunt to the meter was negative 2mv.
2mv is equivalent to about 3amps X 75volts pv = 225watts negative offset
I do not know where the negative bias is coming from.
The shunt wiring is a shielded twisted pair (old telephone underground 6 conductor cable) that runs about 6 feet.
The controller is a renogy 60a.
As he peers thru the smoke, I came to the determination that the offset was being introduced by the meter itself.
Sooo, I decided to eliminate the 12v feed to the meter and wire it per instructions (page 5 2wire system).
ZAP apparently the voltage limits (on page 1) are either backwards or inside out.
I will order a hopefully better upgraded version (DCM120100C) and let ya know what happens.
The old unit will be incorporated into my ongoing eclectic sculpture "Technology Fricassee" .
Maybe you are measuring the current drawn by the meter itself ?
Or maybe you said that ?
But the meter should not draw but maybe 100 or 200 mA at the most ?
Quote from: Barry Fields on April 22, 2024, 11:57:01 AMAs he peers thru the smoke, I came to the determination that the offset was being introduced by the meter itself.
Sooo, I decided to eliminate the 12v feed to the meter and wire it per instructions (page 5 2wire system).
ZAP apparently the voltage limits (on page 1) are either backwards or inside out.
I will order a hopefully better upgraded version (DCM120100C) and let ya know what happens.
The old unit will be incorporated into my ongoing eclectic sculpture "Technology Fricassee" .
Take a look at Peacefair PZEM-025(built in shunt) which is a display type - I have two of those .
The PZEM-017( external shunt) which I also have is just the monitor device with no display and I have it connected to an ESP32 flashed with Tasmota which makes it super easy to interface and then has it's own built in webpage.
I have details of these on various videos on my youtube page.
https://youtu.be/cKJKUMLyjLM?si=_d_mc22SQZnJ3zWE
https://youtu.be/TbLLrlZ3deI?si=x_Af1dzLublTDVjx
Larry
Larry, what do you use to flash your ESP32 ?
What "system" do you use ?
Quote from: boB on April 22, 2024, 05:21:17 PMLarry, what do you use to flash your ESP32 ?
What "system" do you use ?
Any ESP32 development board ( there are many and they only cost $5 ) you can just plug into its micro usb jack with a regular usb to micro cable. Then just plug it into the computer. They actually made it super easy to flash Tasmota directly from a webpage though you need to use Chrome browser to do that. On some esp boards you need to press a boot button in the board first when flashing .
https://tasmota.github.io/install/
The nice thing about tasmota is it supports so many different sensors - makes life easy ! Once flashed it connects to your router and you have a wifi web page from it.
https://tasmota.github.io/docs/
Larry
Quote from: Barry Fields on April 22, 2024, 11:57:01 AMAs he peers thru the smoke, I came to the determination that the offset was being introduced by the meter itself.
Sooo, I decided to eliminate the 12v feed to the meter and wire it per instructions (page 5 2wire system).
ZAP apparently the voltage limits (on page 1) are either backwards or inside out.
I will order a hopefully better upgraded version (DCM120100C) and let ya know what happens.
The old unit will be incorporated into my ongoing eclectic sculpture "Technology Fricassee" .
Here is the Aliexpress Peacefair store - they have many different DC monitors https://peacefair.aliexpress.com/store/1101058977?spm=a2g0o.detail.1000061.1.7d21tWvdtWvdXJ
Thanks Larry, I appreciate your input. I did look at the pzem-25. It appears to have a built in shunt. Is an external shunt a straightforward implementation.
The biggest problem I have (excluding mental issues) is the dimensions of the unit. Attached is a photo of my living room control panel. I would have to enlarge the lower right hole in that 1/8" aluminum plate to accommodate the pezm-25 unit.
All good info but I will first try the same size DCM120100C.
Nice command central you have there Barry ! And nice and neat compared to the mess I have here - ha ha !
Larry
Quote from: Barry Fields on April 22, 2024, 07:35:15 PMI did look at the pzem-25. It appears to have a built in shunt. Is an external shunt a straightforward implementation?
? external shunt question above.
Thanks Barry
Quote from: Barry Fields on April 24, 2024, 12:14:30 PMQuote from: Barry Fields on April 22, 2024, 07:35:15 PMI did look at the pzem-25. It appears to have a built in shunt. Is an external shunt a straightforward implementation?
? external shunt question above.
Thanks Barry
I am not understanding your question. Are you asking if pzem-025 has internal shunt - yes.I don't think it takes an external shunt - just four connections - 2 for 5 to 12v power to run meter and 2 for the negative power wire running through it.
Thanks Larry,
I needed a meter that could stay in my living room with the shunt mounted 10 ft away in the outside battery enclosure.
I can send you a new pzem-017 with shunt if you pay shipping - but it needs an esp8266 or esp32 , rs485 adapter ( unless you do a mod on it to eliminate rs485 ) , and of course you need to have wifi for it to connect to . But then you can monitor with a phone or computer anywhere in wifi range.
Larry
I do appreciate the offer but I have no practical experience with communication protocols. I am an 74 year old analog hardwire kinda guy. My solar system presently has NO wifi/RS485 or any other digital interfaces. For me to come up to speed on that stuff,however much I would like to expand my knowledge, it would probably be the last thing I do (literally).
I do not want my tombstone to read "Just when he started to understand modbus". ;)
Just installed my new DCM-120100C meter.
Externally the same as the older DCM-9040. Fits in the panel hole just fine. External 100a 75mv shunt placed in the low side PV total to charge controller.
The new calibration procedure is much more straight forward if ya carefully read the instructions provided.
Seems to be performing well for monitoring PV power delivered by the panels to the charge controller.
I have no use for the AH or SOC readings so can make statement concerning them.
Quote from: Barry Fields on April 24, 2024, 08:50:42 PMThanks Larry,
I needed a meter that could stay in my living room with the shunt mounted 10 ft away in the outside battery enclosure.
I opened up my a 100A PZEM-25 looking for an undocumented UART (didn't find one ). But to your need, I found the sense wires come from the board and are soldered to the shunt. You could extend the sense wires as needed. Not sure what that will do to calibration. May need to change the shunt resistor or live with some inaccuracy.
Quote from: Barry Fields on May 20, 2024, 10:39:59 AMJust installed my new DCM-120100C meter.
It is still going well. Tapers to close to zero at night (moon shine)
Quote from: Hockey on May 27, 2024, 01:00:21 PMopened up my a 100A PZEM-25 looking for an undocumented UART (didn't find one ). But to your need, I found the sense wires come from the board and are soldered to the shunt. You could extend the sense wires as needed. Not sure what that will do to calibration. May need to change the shunt resistor or live with some inaccuracy.
Good info , but I have resolved my issue. If Mine blows up, I shall return here.