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IoT project : Smart home automation with energy monitoring system

Cindy_1998

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Hi, I want to confirm whether my schematic diagram is correct or not before I test my project. I cannot test the connection using the simulation because I use a new component, PZEM-004T. I have found an IoT project that used the same component, PZEM-004T. However, I also use the AC Light Dimmer component as I want to reduce the power consumption of the light bulb.

Here I attach my schematic diagram, the datasheet of PZEM-004T and AC Light Dimmer.
Datasheet of PZEM-004T
Datasheet of AC Light Dimmer
Schematic Diagram.jpg
 

betwixt

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It might work but I would doubt it.

The PZEM module has an RS485 interface so you probably need to convert it plain 3.3V level serial format.
The dimmer module seems to use a triac so it will phase control the switching and cause problems with the current transformer waveform.
You would have to use an incandescent light bulb which seems to be inefficient in view of what you are trying to achieve.

Also be aware that power consumption is not directly proportional to light output. For example, at 25% power the light may not operate at all. at 50% power it might be very dim and only at high power levels would it give any significant illumination.

Tell us exactly what you want it to do and importantly, tell us the type and rating of the light bulb, then we can give more targeted advice.

Brian.
 

00kam

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hello
the connection between load terminals of the dimmer and light bulb is wrong i see from your schematic diagram you connected (L-N mains terminal directly to load terminals of the dimmer which is the wrong)

kamal
 

betwixt

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Kamal is correct, I missed that. The load goes in series with the dimmer output, you have it wired across the line input.
My other points are still valid!

Brian.
 

00kam

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Kamal is correct, I missed that. The load goes in series with the dimmer output, you have it wired across the line input.
My other points are still valid!

Brian.
Hello
The load (light bulb)goes in series with the dimmer output and T.C . but i note another some thing strange in the ESP8266 NODE MCU dose lib of it could generate zero -cross detector signal which dimmer needs as i know (Z-C) signal is generate from mains power only ( low power rectifier brigade plus two high resistance you can say over 100k ) while the ESP8266 NODE MCU is supplied from +5 volt . some thing is still not clear .

kamal
 

Cindy_1998

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It might work but I would doubt it.

The PZEM module has an RS485 interface so you probably need to convert it plain 3.3V level serial format.
The dimmer module seems to use a triac so it will phase control the switching and cause problems with the current transformer waveform.
You would have to use an incandescent light bulb which seems to be inefficient in view of what you are trying to achieve.

Also be aware that power consumption is not directly proportional to light output. For example, at 25% power the light may not operate at all. at 50% power it might be very dim and only at high power levels would it give any significant illumination.

Tell us exactly what you want it to do and importantly, tell us the type and rating of the light bulb, then we can give more targeted advice.

Brian.
Thank you so much for your reply. Actually, I want to first monitor the power consumption of a 12W LED light bulb using PZEM-004T. If the power consumption reaches the limit, I want to code it to make the light bulb becomes dimmer automatically using the AC light dimmer. For the schematic diagram, I only refer to two different projects and combine them, that's why I'm not sure whether I do that correctly or not.

Can you explain more about this? "The PZEM module has an RS485 interface so you probably need to convert it plain 3.3V level serial format."
 

Cindy_1998

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hello
the connection between load terminals of the dimmer and light bulb is wrong i see from your schematic diagram you connected (L-N mains terminal directly to load terminals of the dimmer which is the wrong)

kamal
Yes, but how do I need to connect the dimmer to load terminals and L-N terminals separately as the load must be connected to L-N terminals and CT, and connected to PZEM-004T?
--- Updated ---

Hello
The load (light bulb)goes in series with the dimmer output and T.C . but i note another some thing strange in the ESP8266 NODE MCU dose lib of it could generate zero -cross detector signal which dimmer needs as i know (Z-C) signal is generate from mains power only ( low power rectifier brigade plus two high resistance you can say over 100k ) while the ESP8266 NODE MCU is supplied from +5 volt . some thing is still not clear .

kamal
I have found about that but I refer to a project that had been done by someone, where he used NodeMCU and the dimmer to control the brightness of the light bulb.

Here I attach the schematic diagram from the video and also the link of the video.
NodeMcu AC Light Dimmer | Part #1 | Tutorial # 32
NodeMCU AC light dimmer.jpeg
 
Last edited:

betwixt

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I wouldn't bother trying, the LED light bulb almost certainly won't work with that dimmer and even if it did, the current transformer would not produce a good enough output to be usable. Inside most LED lamps there is a current regulator which would 'fight back' at your attempts to dim it. Each of the two projects would work on their own for their designed purposes but not together and for an LED load.

A current transformer specification assumes a sine wave current is passing through its primary and it induces a measurable voltage across a load (aka 'burden') on the secondary side. If you use a triac or SCR to control the AC as the dimmer does, it 'chops' the waveform so that part of the cycle is not conducted. The overall effect is that the power to the load is reduced because it isn't there all the time but by rapidly interrupting the current, it breaks the sine waveform and will produce an unpredictable output from the current transformer.

The data sheet is misleading, it states the PZEM module uses RS485 protocol but also shows it having a TX and RX pin. RS485 is a bi-directional electrical specification, not a protocol and it uses two differential signal lines sharing TX and RX function. If it doesn't use RS485 but uses standard full duplex serial data instead, you still need a level shifter to convert between the 5V signal it produces and requires and the maximum 3.3V the ESP8266 uses. If you connect them without a converter the ESP8266 (nodeMCU) will be destroyed!

Brian.
 

00kam

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Yes, but how do I need to connect the dimmer to load terminals and L-N terminals separately as the load must be connected to L-N terminals and CT, and connected to PZEM-004T?
--- Updated ---



I have found about that but I refer to a project that had been done by someone, where he used NodeMCU and the dimmer to control the brightness of the light bulb.

Here I attach the schematic diagram from the video and also the link of the video.
NodeMcu AC Light Dimmer | Part #1 | Tutorial # 32
View attachment 166897
this is correct connection
kamal
 

Cindy_1998

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I wouldn't bother trying, the LED light bulb almost certainly won't work with that dimmer and even if it did, the current transformer would not produce a good enough output to be usable. Inside most LED lamps there is a current regulator which would 'fight back' at your attempts to dim it. Each of the two projects would work on their own for their designed purposes but not together and for an LED load.

A current transformer specification assumes a sine wave current is passing through its primary and it induces a measurable voltage across a load (aka 'burden') on the secondary side. If you use a triac or SCR to control the AC as the dimmer does, it 'chops' the waveform so that part of the cycle is not conducted. The overall effect is that the power to the load is reduced because it isn't there all the time but by rapidly interrupting the current, it breaks the sine waveform and will produce an unpredictable output from the current transformer.

The data sheet is misleading, it states the PZEM module uses RS485 protocol but also shows it having a TX and RX pin. RS485 is a bi-directional electrical specification, not a protocol and it uses two differential signal lines sharing TX and RX function. If it doesn't use RS485 but uses standard full duplex serial data instead, you still need a level shifter to convert between the 5V signal it produces and requires and the maximum 3.3V the ESP8266 uses. If you connect them without a converter the ESP8266 (nodeMCU) will be destroyed!

Brian.
Thank you for explaining! If I use current sensor and voltage sensor instead of PZEM-004T, can I still combine them with the dimmer?
 

betwixt

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Possibly but the circuits become considerably more complicated. It is easy with DC but high voltage AC is much harder.

First, confirm the light bulb will actually work with a dimmer at all. Most will just flicker then stop working as the power to them is constricted. Don't forget that dimmers do not reduce the voltage, they only reduce the time that current can flow through them. With an incandescent light bulb the thermal momentum of the hot filament makes it appear to just get dimmer as the 'on' periods are reduced but inside an LED light bulb there is a power supply and regulator which will react quite differently.

Brian.
 

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