MPDMv4 - Universal AC MAINS Dimmer

For any new orders/requests please feel free to use as usual: tech at esp8266-projects.com. 
   
    MPDMv4 Boards are also available on Tindie: AC MAINS Dimmer - MPDMv4

--------------------------------------------------- DISCLAIMER --------------------------------------------------

WARNING!! You will play with LIVE MAINS!! Deadly zone!! 

      If you don't have any experience and are not qualified for working with MAINS power I will not encourage you to play arround!. The author take no responsibility for any injury or death resulting, directly or indirectly, from your inability to appreciate the hazards of household mains voltages.

   The circuit diagrams are as accurately as possible, but are offered with no guarantees whatsoever. 

    There is no guarantee that this design meets any Rules which may be in force in your country so please check before your local rules/regulations.

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MPDMv4 by ESP8266-Projects.com is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.  

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And the story behind:



  EVOLUTION.

  The next step in the MAINS Power Dimmer/Switch series.

   One of the main problem that people has been complained about was the fact that a simple MAINS Power Dimmer/Switch unit like the basic one presented last year is using sometime too much resources from a already overloaded application MCU/processor:

MPDMv3 - MAINS Dimmer/Switch with Phase detection

   One of the scenarios, directly related with ESP8266 is about the limited timers capabilities that you have. For example,  if you want to implement a proper web server to directly serve your webpages from ESP8266 you are automatically using one timer. If you want to start using the second one for your ZCD processing ...well...it's becoming very tricky. Very.

   Don't uderstand me wrong, a bigger, better MCU can do it probably very well, but even then if you have the chance to free some resources easily, do it!. And  I really cannot see a ESP8266 acting as a App MCU (webserver, data logger, MQTT client, etc, etc) and doing reliable also other demanding functions as  Processing Zero Crossing Detection.


   SOLUTION? 

    I can see only one, and it is a lesson learned many years ago: keep your real-time processing functions away from your Application MCU/Processor. To do that we just need to move the ZCD processing function from the ESP8266/whatever MCU you want to the MPDM Driver itself:

MPDMv4 - MAINS Phase detection and ZCD processing

   What means that? means that in this new configuration our ESP8266 will be free from any type of real-time ZCD processing that is related with the MAINS Dimming process, you just  need to send to the MPDMv4 driver a voltage (Vcontrol) in a pre-established range (0-3V for example) that will correspond with different desired Dimming levels.

 What we have obtained? A UNIVERSAL MAINS Power Dimmer driver that can be used with any MCU you might want or even no MCU at all. You can dimm it even with a simple Potentiometer at input, no programming, no code, no nothing!!


Legend:  
PURPLE  - Phase detector output
BLUE      - Reversed phase signal (normalised)
Yellow     - Triac Driver CMD signal (PWM)
 

Vcontrol = 0, CMD Duty cycle=6%

Vcontrol = 2V, CMD Duty=50%

Vcontrol = 2.8V,  CMD Duty=96%

  How can be done that? Easy. Use PWM or a DAC, your choice. For ESP8266 I will recommend you to use a DAC, like the MCP4726  or, why not , the MCP4728, for a full 4 Channel MAINS Dimmers solution. PWM in case of the ESP8266..let's say that is has some limitations that you will discover very soon that you don't like :)


The mains advantages of using DAC?

Notable: 

1. Very low to zero overhead on the App MCU
2. High precision (DAC from above are 12 bit!! - 4096 levels of dimming!!)
3. You can use the "set-and-forget" technique using DAC internal nonvolatile memory (EEPROM) and have the same level on the next power-off/on cycle.


  IMPLEMENTATION


   SCHEMATICS

    As the only functional difference between the previous MPDMv3 MAINS Dimmer and the new MPDMv4 is the presence of the ZCD function onboard, basically, without some small bits and pieces around like the MOV protection circuit, you can see it exactly as it is: a MPDMv3 with a ZCD circuit onboard:

MPDMv3 - Phase detection and Triac control

Zero crossing detector circuit

   MPDMv4 PCB:

MPDMv4 PCB

   As you can see from the above picture, it was carefully designed with proper MAINS isolation from the rest of the driver, you can see even the extra isolation slots done for a even bigger Creepage distance.

And because I know this terms still creates some confusion, short definitions below:

CLEARANCE is the shortest distance in air between two conductive parts.
CREEPAGE distance means the shortest distance along the surface of a solid insulating material between two conductive parts.

 A creepage distance cannot be less than the associated clearance so that the shortest creepage distance possible is equal to the required clearance. However, there is no physical relationship, other than this dimensional limitation, between the minimum clearance in air and the minimum acceptable creepage distance.


And the new, freshly baked result:

MPDMv4 - MAINS Power Dimmer/Switch with Phase detection and ZCD Processing

Next time we will move on to the Software side, to see what is going on with our Webserver interface & stuff.

MPDMv3 - WIFI Mains Power Dimmer / Switch - Web Interface

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WARNING!! You will play with LIVE MAINS!! Deadly zone!! 

      If you don't have any experience and are not qualified for working with MAINS power I will not encourage you to play arround!. The author take no responsibility for any injury or death resulting, directly or indirectly, from your inability to appreciate the hazards of household mains voltages.

   The circuit diagrams are as accurately as possible, but are offered with no guarantees whatsoever. 

    There is no guarantee that this design meets any Rules which may be in force in your country so please check before your local rules/regulations.

----------------------------------------------------------------------------------------------------------------------------  

     For any new requests please feel free to use as usual: tech at esp8266-projects.com.
 
     If you want to order MAINS POwer Dimmer/Switch bare PCBs only, you can also do it directly at Dirty PCBs, our preferred PCB House:

http://dirtypcbs.com/view.php?share=6077&accesskey=6d39638a132d55b23b6d2eab8d095bba

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     As I promised in the last article about the new MAINS Dimmer / Switch Module, Today we will continue with designing the Web interface access.


      What we will need:  

• CBDB Board or any other ESP8266 you may like 
•  USB adapter (take a look on Part 1 for details about the USB Adapter 
•  Main Power Dimmer/Switch module (MPDMv3)

MAINS Power Dimmer / Switch Module - MPDMv3 - Connections

CBDB Evolution DevBoard

     Because I don't like to have flying MAINS wires on my workdesk I have created a temporary separate MPDMv3 Module Box, containing all the MAINS part of the story :).

Isolated MAINS unit - keep your fingers away from the Deadly zone !

      Remember, Safety First! And also more relaxing knowing that is no Russian Roulette wire game on progress on my table. Shit happens all the time, but at least let's try to reduce the chances to hit badly the fan too often :)

Live Testing on progress

   In the Box above is enough space for all the parts going inside, including ESP8266 module, power supply, Dimmer Module, Choke, etc, but at this stage I find it easier to connect them together like that.



MPDMv3 Web Server Software

For programming CBDBv2 Board and uploading the driver and the software we will continue to use the LuaUploader as before. 


1. Define used GPIO pin:

      outpin=7                                                       -- Select Triac Command pin - GPIO13
      gpio.mode(outpin,gpio.OUTPUT)
      gpio.write(outpin,gpio.LOW)                       -- Triac OFF
      inpin=6                                                         -- Zero crossing detector input - GPIO12 
      gpio.mode(inpin,gpio.INT,gpio.PULLUP)   -- attach interrupt to ZCD




  2. Zero Cross Detector function and Triac command


      For a more detailed explanation how Zero cross detection circuit works please take a look at the previous MPDMv3 article.

      function zero_cross()
           dt = 76*dim
           --print("Zero cross detected!")
           stat = "ON"
           tmr.delay(dt)                                 -- Firing delay time calculated above
           gpio.write(outpin,gpio.HIGH)     -- Triac ON - Zero cross detected
           tmr.delay(100)                              -- Triac ON - Propagation time 
          gpio.write(outpin,gpio.LOW)        -- Triac OFF - let's be sure it's OFF before next cycle :)
          tmr.wdclr()
          return stat
     end



3. WEB Server

srv=net.createServer(net.TCP)
srv:listen(80,function(conn)
   conn:on("receive", function(conn,payload)
      --debugging output only
      -- print(payload)
      if (string.find(payload, "GET / HTTP/1.1") ~= nil) then
         --print("GET received")
         sendPage(conn)
      else
         swstat={string.find(payload,"cmd=")}
         --If POST value exist, set power switch status
         if swstat[2]~=nil then
            --print("Command received: " .. payload)
            PwrSW(swstat,payload)
            sendPage(conn)
         end
      end
   end)
   conn:on("sent", function(conn)
      conn:close()
      conn = nil -- clear and allow the garbage collector to free the memory
      --print("Connection closed")
     
   end)
end)
 


4. Send page function based on received requests

function sendPage(conn)
   conn:send('HTTP/1.1 200 OK\n\n')
   conn:send("<META HTTP-EQUIV=\"REFRESH\" CONTENT=\"5\">")
   conn:send('<!DOCTYPE HTML>')
   conn:send('<html>')
   conn:send('<head><meta content="text/html; charset=utf-8">')
   conn:send('<LINK href="http://www.instructables.com/files/orig/FGU/L48I/I98BK1X6  
                       /FGUL48II98BK1X6.css"')
   conn:send('rel="stylesheet" type="text/css">')
   conn:send('<title>ESP8266 - Power Switch Controller</title></head>')
   conn:send('<body><center><h1>ESP8266 MAINS Power Dimmer Controller</h1></center>')
   conn:send('<br /><br />')
   conn:send('<form action="/" name="dimmer" oninput="outputUpdate(cmd.value)" 
                     method="POST">')
   conn:send('<font color=red><b>ON </b></font><input style="width:550px; height:50px" 
                     type="range" name="cmd" id="cmd" value="')
   conn:send(status)
   conn:send('" min=1 max=128 step=1 />')
   conn:send('<font color=red><b>OFF</b></font></form>')
   conn:send('<br><center>Dimmer Value: <b>')        
      conn:send(status)
      conn:send(' pts</b></center>')
   conn:send('<script type="text/javascript">')
   conn:send('function outputUpdate(dim) {document.querySelector("#cmd").value = dim;')
   conn:send('document.forms[0].submit();}</script>')
   conn:send('</body></html>')
end
 
 CSS file created for this example is just for fancy decorations. If you don't like it you can very easy change the style attributes or add local ones.



5. Check received Dimmer value and update status

     function PwrSW(swstat,payload)
           gpio.mode(outpin,gpio.OUTPUT)
           newstat=string.sub(payload,swstat[2]+1,#payload)
           status = tonumber(newstat)
           print("Dimmer Value:" ..  status)
    end





4. Main code

       status = 60                   -- around 50% - choose your desired start value.
       newstat = 60
        outpin=7                     -- Select Triac Command pin - GPIO13  
        gpio.mode(outpin,gpio.OUTPUT)
        gpio.write(outpin,gpio.LOW)  -- Triac OFF
        inpin=6                      -- Zero crossing detector input - GPIO12 
        gpio.mode(inpin,gpio.INT,gpio.PULLUP)  -- attach interrupt to ZCD
 
       gpio.trig(inpin,"up",zero_cross)                 -- ZCD interrupt attached - trigger on falling edge
       print(wifi.sta.getip())                                  -- print our new MPDMv3 WebServer IP



      For testing, just save the code on ESP as 'dimserver.lua', restart ESP and run:   
 
            dofile("dimserver.lua")      -- Start the Dimmer Listening WebServer
               =wifi.sta.getip()              -- find the IP Address where your Web Server will be

  

     Open your favorite Web browser and type your new MPDMv3 Web Server IP address. If all ok, should look something like below :

MPDMv3 Web Interface

If you want the MPDMv3 software to start automatically when your CBDB module starts or reboots, then you neet to create and add some lines in your 'init.lua' file:
  
          dofile("dimserver.lua")  -- Start automatically the Dimmer Listening WebServer



Save the code on ESP as 'init.lua', restart ESP. It should reboot and restart automatically the program.

A short video presentation, testing the Web Interface:

P3 - WIFI Mains Power Dimmer / Switch with CBDBv2

UPDATE!! UPDATE !!

New released MPDMv4 (MAINS Power Dimmer) Driver Board !

----------------------------------------------------------------------------------------------------------------------------

WARNING!! You will play with LIVE MAINS!! Deadly zone!! 

If you don't have any experience and are not qualified for working with MAINS power I will not ecourage you to play arround!

----------------------------------------------------------------------------------------------------------------------------

   For any new requests please feel free to use as usual: tech at esp8266-projects.com.
     If you want to order MAINS POwer Dimmer/Switch bare PCBs only, you can also do it directly at Dirty PCBs, our preferred PCB House:

http://dirtypcbs.com/view.php?share=6077&accesskey=6d39638a132d55b23b6d2eab8d095bba

-----------------------------------------------------------------------------------------------------------------------------

    For that ones of you that have already read my articles related with MAINS Power Switching

Web Power Switch for MAINS and the WIFI MPSMv2 MAINS Switch DevBoard

 you remember that the above modules were ON/OFF switching only.

    Now it's about time to talk also about what many of you has asked for: DIMMING!
   It's a total different story, liitle bit complicated but, as you will see, not so hard to understand.

 
General considerations: 

    There are several types of dimmers generally available. These are used for resistive, and inductive loads, such as incandescent,cold cathode and low voltage (inductive) lamp sources. Note that not all electronic transformers used for low voltage lamps are suitable for dimming by Triac or Thyristors dimmers. In case of Thyristors you need 2 of them as Thyristor is a Unidirectional device and because AC power flows in both directions! 
    
   Why using Thyristors? One of the reasons is that they are available in higher power ratings than Triacs and are more robust. A 4-500 A to 1kA ratings is something common for Thyristors. 
Usually you will find this kind of Thyristors in Industrial applications, not exacty a hobbist part.  
 Just look, for example,  at the specifications of ABB 5STP27H2801  and you will understand why :)

  I don't remember a highly available Triac rated more than 40A. BTA40-700B is a good example.




 
  For resistive loads ON-OFF only jobs (no dimming required) a winning combination is between  MOC304X for  Triac driver (Zero voltage crossing one) and a good quality Triac, decently sized at the power needs. 

   In case of dimming you DON'T want to use a zero crossing voltage one! And this is because of the way the dimming process is going and depending on our own ZCD (zero cross detection) function. In our case zero cross detection is done by the biphase optocoupler as in the schematic below

Zero Cross Detection output example

    Mains power is comprised of an alternating current that flows in one direction and then in the other, along the cable, at the rate of 50 or 60 cycles per second.

   The number of cycles in one second is called the frequency.  The frequency is given in a unit called hertz (symbol Hz) where 1 Hz = 1 cycle per second . 

   The value 50 or 60Hz is dependent on the countries power system. The current alternates back and forth changing direction at the zero point.

    If we will to look at the waveform (yellow) with the Osciloscope it would appear as a sinusoidal shape. Drawing a line through the middle and this is what is called the zero crossing point. At this instant in time no current is flowing in either direction.

MAINS 50Hz and ZCD waveforms

   The Triac is electronically synchronized with the help of the ZCD to turn the power ON or OFF. By chopping the waveform at the zero-crossing point, smooth dimming can be achieved without the lamp flickering. This turning on and off of the power device occurs every time the mains crossing point is reached (half phase), 100 or 120 times per second (50 or 60Hz).

Firing Triac at 50%

   ZCD determines the point in time (Firing delay time) at which they turn ON (conduct). The ON state continues until the next zero-crossing point, at which point the Triac turns itself OFF. The command circuit then provides a delay, which equates to the dimness of the lamp, before turning the control device back on. The slight capacitance of the load, filters the chopped waveform resulting in a smooth light output.


NOTE: If you notice that the 50Hz AC Voltage repesented up (yellow) is not around 240VAC and is nor pure sinusoide as should be, it's a simple explanation: I didn't want to put Osciloscope directly on MAINS. For very simple reasons. But this is not affecting at all the general view of the process.






What we will need:

• CBDB Board or any other ESP/Arduino /MSP/ARM/Whaterver Board you may like

• USB adapter (take a look on Part 1 for details about the USB Adapter)

• Main Power Dimmer/Switch module (MPDMv3 - details below)
  

Main Power Dimmer/Switch module (MPDMv3)

 

     This time the MAINS Dimmer switch module was designed as a standalone unit, not including the ESP8266 anymore, as people were asking for a more general usage one that can be used with existing Setup/Environments. 

    Because the MPSMv2 was designed more as a DevBoard for MAINS switching application and the FUSE and MAINS input / output /filtering unit was keept separatelly  has created some confusion and a lot of talks about, Hackaday thread included :).

    So, this time, you have on the same board, fuse and connectors to directly connect de MPDMv3 module to MAINS, Lightbulb/Lamp and your MCU Board. 

MPDMv3 - Schematic

MPDMv3 - MAINS Dimmer/Switch Module

   Both signals, phase detect (PHS) for ZCD and Triac command (CMD) are fully optocoupled and you have a proper galvanic separation between the low side and the MAINS side voltage, but,  as a general practice DO NOT TOUCH any part of the circuit as long as MAINS power it's applied!! The scope of LED1 is just to help you in the testing phase process, it does not have any other sense on dimming.

Proper clearance and creepage distance were also taken in consideration when PCB was designed:

MPDMv3 - PCB - Bottom side

MPDMv3 Software

For programming CBDBv2 Board and uploading the driver and the software we will continue to use the LuaUploader as before. 


1. Define used GPIO pin:

      outpin=7                                                       -- Select Triac Command pin - GPIO13
      gpio.mode(outpin,gpio.OUTPUT)
      gpio.write(outpin,gpio.LOW)                       -- Triac OFF
      inpin=6                                                         -- Zero crossing detector input - GPIO12 
      gpio.mode(inpin,gpio.INT,gpio.PULLUP)   -- attach interrupt to ZCD



2. Zero Cross Detector function


   As you have seen above on the Osciloscope, zero crossing is the moment when the sinusoide goes through zero. After each zero crossing there is one full half of the sinuswave available to send through the Triac to the Load.

   So what the software needs to do is to detect the zerocrossing, and then wait for a set amount of time on that sinuswave to switch on the TRIAC.


We have a 50Hz VAC that means is 50 waves per second.
Each sinuswave thus takes 1000ms/50=20ms
They are 2 sinus peaks in a wave.  That means that after every zero crossing detection there is a 10ms period that we can regulate.
If we switch Triac directly at the beginning of that period, the load will receive full power
If we do it at the end of that 10ms period the load will receive none and if we do it halfway, the load will receive half power.



Now, how can we obtain the desired number of dimming steps?

If you look at the above explanation you know already the answer: we will divide the 10ms to the number of the steps we want and that's it. The obtained value can be tweaked a bit, depending on how is really looking your AC MAINS and how clean it is, filtering, delays, etc, but that's the dimming steps value you need to start with.

Let's assume we have:
Dimming steps = 128
Waveform Time= 10 ms
Step = 10000/128 = 78

Total dim time then is calculated as desired dimming steps * step value.

Also what we need to take in consideration after we fire the Triac is the Triac ON Propagation time (the time Triac needs to become fully ON).


      function zero_cross()
           dt = 76*dim
           --print("Zero cross detected!")
           stat = "ON"
           tmr.delay(dt)                                 -- Firing delay time calculated above
           gpio.write(outpin,gpio.HIGH)     -- Triac ON - Zero cross detected
           tmr.delay(100)                              -- Triac ON - Propagation time 
          gpio.write(outpin,gpio.LOW)        -- Triac OFF - let's be sure it's OFF before next cycle :)
          tmr.wdclr()
          return stat
     end





3. Fading function for testing mode


     function fading()
         if(dim_up==1) then dim=dim+1
              else dim=dim-1
         end
         if(dim < 10) then dim_up=1 dim=10
              else if (dim > 120 ) then dim_up=0 dim=120
         end
         end 
         print("Dimmer level : " .. dim)
         print("Fading mode  : " .. dim_up)
         tmr.wdclr()
    end




4. Main code

       dim = 120                                                          -- Dimmer level - smaller value is brighter
       dim_up=0                                                          -- Fading direction - for test  run
       gpio.trig(inpin,"up",zero_cross)                       -- ZCD interrupt attached - trigger on falling edge
       tmr.alarm(0, 100, 1, function() fading() end)     --timer for testing mode


For testing, just save the code on ESP as 'dimmer.lua', restart ESP and run:   
            dofile("dimmer.lua")  -- Start the Dimmer Testing  mode

If you want the MPDMv3 software to start automatically when your CBDB module starts or reboots, then you neet to create and add some lines in your 'init.lua' file:

            dofile("dimmer.lua")  -- Start the Dimmer Testing mode

Save the code on ESP as 'init.lua', restart ESP. It should reboot and restart automatically the program.

Testing Zero Cross Detector

First test - Dimming a Lamp

UPDATE!! UPDATE !! UPDATE !!

As requested, please find below MPDMv3 BOM:

No	Part	Value	Package	Description
1	R1	470	R1206	RESISTOR, European symbol
2	R2	360/1W	0204/7	RESISTOR, European symbol
3	R3	470/1W	0204/7	RESISTOR, European symbol
4	R4	470	R1206	RESISTOR, European symbol
5	R5	39/1W	0207/5V	RESISTOR, European symbol
6	R6	47k/1W	0207/10	RESISTOR, European symbol
7	R7	47k/1W	0207/10	RESISTOR, European symbol
8	R8	10k	R1206	RESISTOR, European symbol
9	C1	0.01uF/400 X2	C075-032X103	CAPACITOR, European symbol
10	C2	0.05uF/400V	C075-032X103	CAPACITOR, European symbol
11	IC1	MOC3021	DIL06B	6-Pin DIP Optoisolators Triac Driver Output
12	IC2	SFH620A	DIL04	Optocoupler, Phototransistor Output, AC Input
13	T1	BT137	TO220BV	TRIAC
14	PLD		CHIPLED_1206	LED
15	PWR_IN	DG3XX-02-5.0	DG306-5.0-02P	DG350-3.5-02P
16	SW_OUT	DG3XX-02-5.0	DG306-5.0-02P	DG350-3.5-02P
17	FUSE	5A	SHK20Q	Fuse
18	U$3	1X4	1X4	2mm Header or 2mm socket

That's all for today, next time we will talk about WEB Interface implementation for our MAINS Power Dimmer / Switch Module!