Under & overvoltage relay for AC main power supply

   After I made a test for Measuring AC Main Supply Voltage with Arduino, now I change the sketch for made protection relay with adjustable limits for undervoltage, overvoltage and delay-off time using 3 buttons:

   After power the module, Arduino read and calculate vltage for AC main power supply and if is ok, coil relay is powered:

   If push MENU/OK button, on display is SET

after 2-3 seconds, on display is undervoltage threshold, who cand change using + & - buttons:

    After you push MENU/OK button, is displayed overvoltage thereshold, who cand change using + & - buttons:

   After you pus MENU/OK buttons on display is delay-off time for reconnect coil relay after voltage is outside good range, also you can change value form 1 tp 20 seconds using + & - buttons:

    After you push MENU/OK button, on display is main voltage:

   I write main_voltage_3.ino sketch who made exactlly in picture, but it more easy to understund cases if you see under & overvoltage relay with Arduino movie

Bibliography:

- Releu de protectie la minima si maxima tensiune retea

- Releu de protectie la minima si maxima tensiune retea (2)

- Masurare valoare tensiune retea (2)

- Measuring AC Voltage with an AC to AC power adapter

Measuring AC Main Supply Voltage with Arduino (2)

   In article named Measuring AC Voltage with an AC to AC power adapter from OpenEnergyMonitor I found a interesting solution for measure AC voltage.
   Schematic is

   I use EmonLib library like in article:

   On DSO I see on R1 resistor

and at A2 input of Arduino board (on R4 resistor):

   I use an LED display with 8 digit 7-segment drived by MAX7219 (I present on article namend Modul de afisare cu 8 cifre LED din 7 segmente fiecare controlate de MAX7219

   I use some configuration for LedControl library (dosc at The Arduino LedControl library):

   Test schematic is

   I write main_voltage_emonlib_1.ino sketch and upload in Arduino board:

  I made main supply voltage measured with Arduino (2) movie:

Measuring AC Main Supply Voltage with Arduino

   If you need to measuring AC main supply voltage with Arduino must made some calculation.

   I use a simple schematic:

   I can directly measure the DC voltage on R1 resistor. I use internal reference from Arduino Uno board (compatible board with ATmega328 microcontroller) so maximum value for U2 can be

U2 = U1*(R1+R2)/R1 = 1.1*(1+22)/1=25.3V

  AC voltage U1 so DC voltage U2 = U1*1.41-Udiode

  If we put value in equation

U1 = (U2+Udiode)/1.41

because I use trafo U0 = k * U1.

  For tests, I use a trafo imprinted 220V/2x12V 200mA but if I measeure voltage from secondary coil

I found 11V when main voltage is 220V, so k = 220/11=20. I use an 1N4007 diode and Udiode=0.65V.

  I use an LED display with 4 digit 7-segment drived by TM1637 (who I present on base blog in article named Afisaj cu 4 cifre controlate de TM1637 si Arduino and sketches are at https://github.com/tehniq3/TM1637-display):

   Schematic for display put on Arduino Uno is:

   I write main-voltage_0.ino sketch and upload in Arduino board and I made a movie named main supply voltage measured with Arduino

Home acces using keypad from outside and push button from inside

   I made a system for home acces with delay-off using keypad from outside and push button from inside. I write a sketch for use actuator or solenoid.
   In stand by mode, solenoid (or actuator) is released.
   After I indroduce good code *1234# from keypad actuator is unlocked for 0.7 seconds; about 5 seconds acces is permited, after that actuator is locked for 0.7 seconds. Same cases are when push button from inside.
   If you use solenoid instead actuator, after I introduce good code *1234# from keypad coil solenoid is powered about 5 seconds, after that coil solenoid is released.
   Base test schematic is:

but if you use actuator, schematic is

and if you use solenoid, schematic is

   If you use acces_code_keypad_1.ino sketch, system work like in deblocare usa cu cod din exterior si buton fara retinere din interior movie 

   A comrade, Tommy, made a permanent montage on PCB for actuator:

   I put an alphanumeric LCD1602 display on i2c and an RTC module with DS3231 (or DS1307) and base schematic is:

   If you upload acces_code_keypad_3.ino sketch. in standby mode, on display is hour & date:

and when acces is shared and a open padlock is displayed.

   In movie named door lock acces with code and pushbutton you cand see all I write:

Itron FG209M2 vfd display controlled by Arduino via 2 MAX6921

see about this article on HACKADAY ;)


   I give for tests an old vfd display made by Itron with 20 characters each made with 14 segments, point & comma.

   Janos, who is owner of this vfd display, made a interface with 2 MAX6921 integrated, using this schematic:

and PCB board is

   I redesigned schematic of vfd interface using Eagle PCB software: 

   After I study the datasheet of MAX6921, for send data to vfd display, classical style is:

 but in my case is little different because I have cascaded 2 MAX6921; for put on vfd display letter R on left corner must send this data:

with this notation of segments of character:

   For initial test, I made a simple schematic, using fist time an Arduino Mega board, than Arduino Uno:

   When upload VFD_FG209M2_2MAX6921_test1.ini sketch I see X letter moving from right to left of vfd display, like in video named 

afisaj VFD FG209M2 cu MAX6921 si Arduino:

   I made small steps (create characters, like in application note for MAX6954 (see https://www.maximintegrated.com/en/app-notes/index.mvp/id/3211)

 until I simulate a clock with calendar and temperature and humidity using VFD_FG209M2_2MAX6921_test3j3c.ini sketch, see movie named afisaj VFD FG209M2 cu MAX6921 si Arduino (9)

   Finally, I put in schematic an RTC module with DS3231 (works fine with DS1307, too) and DHT22 module (AM2302 sensor + 4k7 resistor between +5V and DATA pin) for humidity and temperature:

   Using RTC_DHT_VFD_FG209M2_2MAX6921_ver4.ino I have on vfd display next texts:

see clock on VFD FG209M2 display with MAX6921 and Arduino movie:

   Because texts are in my native language (roumanian) I made few changes for have alternative indications:

  I write and upload RTC_DHT_VFD_FG209M2_2MAX6921_ver4a.ino sketch and results can be see in clock on VFD FG209M2 display with MAX6921 and Arduino (2)

NOTE: More details about steps in experiments can be writte in original article !

   I reduce previous sketch and remain just english text for day & day, current sketch is RTC_DHT_VFD_FG209M2_2MAX6921_ver4b.ino and you can see how is now in movie named clock on VFD FG209M2 display with MAX6921 and Arduino (3)

1-March-2021

   I received from Janos new info for display

also I received the schematic for power the VFD: