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The main goal of the project is to create a AC Mains Light dimmer that can automatically control the level of light and keep in in the desired set interval without any external intervention.
Why would you be intrested in such a setup? Well, if you have any interest in hydroponics, photography, or anywhere where you need some sort of constant flood light lamps with precise light intensitity level setup then might be a good idea to take a look :) What we will need:
BH1750FVI Module . Can be ordered in packs of ONE, FIVE or even TEN from the corresponding links. My 10 one was backordered but received it quite quickly.
For programming and uploading the driver and the software we will continue to use the LuaUploader as before.
Connection with the ESP8266 nEXT EVO Board is very easy, as MPU6050 GY-521 Module connector
is fully compatible with the nEXT Bus connector. Depending on how to you
choose you socket type, you can install it on TOP or Bottom of the ESP8266 nEXT EVO Board :
BH1750FVI Module directly connected to the ESP8266 nEXT EVO Board
And the whole project setup, with MPDVv4 AC Dimmer connected on ESP8266 GPIO13 (pin 7):
MPDM v4 + nEXT EVO + BH1750FVI
Closer look, MPDMv4 connected at ESP8266 GPIO13 (Pin7) for PWM control
function set_light() read_input(dev_addr) ll = light - hst --lower level lh = light + hst --upper level if (lux < ll) then p=0 i = i - step if (i<0) then i = 0 end pwm.setduty(7, i) end if (lux >lh) then p=0 i = i + step if (i>880) then i = 880 end pwm.setduty(7, i) end --print("Auto Level Adjust : "..i) --print(ll) --print(lh) if (ll< lux and lux < lh) then if (p<1) then p=1 end if (p<2) then print(string.format("\nLight Level: %0.2f lux",lux)) print("Auto Level Adjust : "..i) p=2 end end end
Main Program --PWM testing for MPDMv4 AC Dimmer Board
In the process of choosing of some Light Sensors for one of the new projects that will involve the nEXT EVO Board and also the MPDMv4 Mains Dimmer somebody suggested to give a try also to the ROHM BH1750FVI Sensor.
As you can see on the picture above, on the tiny board, you have the BH1750FVI Sensor, a LDO regulator some filtering caps and pull-up resistors and that's it!
BH1750FVI Module - Bottom
The bottom side is bringing us more good news, the Module interface connector is fully compatible with the nEXT EVO Bus!
BH1750FVI Overview
BH1750FVI is an digital Ambient Light Sensor IC for I2C bus interface. This IC is the mostly used to obtain the ambient light data for adjusting LCD and Keypad backlight power of Mobile phone. This is great as we are looking forward to use it for Automatic light adjustment using the MPDMv4 AC Dimmer board :)
Features
I2C bus Interface ( f / s Mode Support )
Spectral responsibility is approximately human eye response
Illuminance to Digital Converter
Wide range and High resolution. ( 1 - 65535 lx )
Low Current by power down function
50Hz / 60Hz Light noise reject-function
1.8V Logic input interface
Native 3.3V Device
No need any external parts
Light source dependency is little. ( ex. Incandescent Lamp. Fluorescent Lamp. Halogen Lamp. White LED. Sun Light )
It is possible to select 2 type of I2C slave-address.
Adjustable measurement result for influence of optical window ( It is possible to detect min. 0.11 lx, max. 100000 lx by using this function. )
Small measurement variation (+/- 20%)
The influence of infrared is very small.
Internal Diagram
BH1750FVI - Internal Diagram
PD - Photo diode with approximately human eye response.
AMP - Integration-OPAMP for converting from PD current to Voltage.
ADC - AD converter for obtainment Digital 16bit data.
Logic + I2C Interface :
- Ambient Light Calculation and I2C BUS Interface. It is including below register.
- Data Register - This is for registration of Ambient Light Data. Initial Value is
"0000_0000_0000_0000".
- Measurement Time Register - This is for registration of measurement time. Initial Value
is "0100_0101".
OSC - Internal Oscillator ( typ. 320kHz ). It is CLK for internal logic.
BH1750FVI Module from above. Can be ordered in packs of ONE, FIVE or even TEN from the corresponding links. My 10 one was backordered but received it quite quickly.
For programming and uploading the driver and the software we will continue to use the LuaUploader as before.
Connection with the ESP8266 nEXT EVO Board is very easy, as MPU6050 GY-521 Module connector
is fully compatible with the nEXT Bus connector. Depending on how to you
choose you socket type, you can install it on TOP or Bottom of the ESP8266 nEXT EVO Board :
BH1750FVI Module directly connected to the ESP8266 nEXT EVO Board
BH1750FVI Driver implementation
1. Init I2C bus/interface
Standard I2C Bus Initialisation function:
function init_I2C() i2c.setup(bus, sda, scl, i2c.SLOW) end
2. WRITE Function - Set BH1750FVI Register config
From BH1750FVI Datasheet :
No active state : pwr_down 0x00
Wating for measurment command : pwr_on=0x01
Reset data register value - not accepted in POWER_DOWN mode : reset=0x07
Continuous modes, no pwr down:
Start measurement at 1lx resolution. Measurement time is approx 120ms:
hi_res_m1=0x10
Start measurement at 0.5lx resolution. Measurement time is approx 120ms.
hi_res_m2=0x11
Start measurement at 4lx resolution. Measurement time is approx 16ms.
lo_res_m1=0x13
Device is automatically set to Power Down after measurement:
Start measurement at 1lx resolution. Measurement time is approx 120ms.
hi_res_m3=0x20
Start measurement at 0.5lx resolution. Measurement time is approx 120ms.
hi_res_m4=0x21
Start measurement at 1lx resolution. Measurement time is approx 120ms.
lo_res_m2=0x23
function setcfg(cfg) i2c.start(id) i2c.address(id, dev_addr ,i2c.TRANSMITTER) i2c.write(id,cfg) i2c.stop(id) end
Somebody sent to me a nice & tiny temperature/humidity sensor breakout board based on the Si7021 IC:
Si7021 Module - Top View
On the Top side we have Si7021 Sensor only.
Si7021 Module - Bottom View
Bottom Side, a 3.3V LDO and a Voltage level shifting circuit that probably makes it 5V tolerant on I2C bus. We will use it at 3.3V so nothing to worry about.
DESCRIPTION
The Si7021 I2C Humidity and Temperature Sensor is a monolithic CMOS IC integrating humidity and temperature sensor elements, an analog-to-digital converter, signal processing, calibration data, and an I2C Interface.
The patented use of industry-standard, low-K polymeric dielectrics for sensing humidity enables the construction of low-power, monolithic CMOS Sensor ICs with low drift and hysteresis, and excellent long term stability.
The humidity and temperature sensors are factory-calibrated and the calibration data is stored in the on-chip non-volatile memory. This ensures that the sensors are fully interchangeable, with no recalibration or software changes required.
The Si7021 offers an accurate, low-power, factory-calibrated digital solution ideal for measuring humidity, dew-point, and temperature, in applications ranging from HVAC/R and asset tracking to industrial and consumer platforms.
Si7021 - Block Diagram
Nice. Looks more or less like SHT21 from Sensirion. And we will see that it is quite compatible (at least on the temp/humidity reading procedure side) with small differences for the rest of registers.
For programming and uploading the driver and the software we will continue to use the LuaUploader as before.
Connection with ESP8266 nEXT EVO Board is pretty straight-forward as the module is fully pin-to-pin compatible with the availavble nEXT Bus connector.
Si7021 Board connected with ESP8266 nEXT EVO DevBoard - TOP view
Si7021 Board connected with ESP8266 nEXT EVO DevBoard - 45 deg view
Software implementation
The Si7021 communicates with the host controller over a digital I2C interface. The 7-bit base slave address is 0x40
Master I2C devices communicate with the Si7021 using a command structure. The commands are listed below in the I2C command table. Commands other than those documented below are undefined and should not be sent to the device.
I2C Command Table
Issuing a Measurement Command The measurement commands instruct the Si7021 to perform one of two possible measurements: Relative Humidity or Temperature.
The procedure to issue any one of these commands is identical. While the measurement is in progress, the option of either clock stretching (Hold Master Mode) or Not Acknowledging read requests (No Hold Master Mode) is available to indicate to the master that the measurement is in progress. The chosen command code determines which mode is used.
Optionally, a checksum byte can be returned from the slave for use in checking for transmission errors. The checksum byte will follow the least significant measurement byte if it is acknowledged by the master. The checksum byte is not returned if the master “not acknowledges” the least significant measurement byte. The checksum byte is calculated using a CRC generator polynomial of x^8+ x^5 + x^4 + 1, with an initialization of 0x00.
The checksum byte is optional after initiating an RH or temperature measurement with commands 0xE5, 0xF5,0xE3, and 0xF3. It is required for reading the electronic ID with commands 0xFA 0x0F and 0xFC 0xC9.
For all other commands, the checksum byte is not supported.
1. Init I2C bus/interface
Standard I2C Bus Initialisation function:
function init_I2C() i2c.setup(bus, sda, scl, i2c.SLOW) end
2. Write Si7021 Register Function
write_Si_Reg = function (dev_addr, set) i2c.start(0x0) i2c.address(0x0, dev_addr ,i2c.TRANSMITTER) i2c.write(0x0,set) i2c.stop(0x0) tmr.delay(5000) end
3. Read Si7021 Register Function
read_Si_Reg = function (dev_addr) i2c.start(0x0) i2c.address(0x0, dev_addr,i2c.RECEIVER) tmr.delay(5000) c = i2c.read(0x0,2) i2c.stop(0x0)
rval = (bit.lshift(string.byte(c, 1), 8) + string.byte(c, 2)) status = bit.band(rval,3) --save status bits rval = bit.band(rval,65532) --clear status bits return rval, status end
4. Measuring Relative Humidity
Once a relative humidity measurement has been made, the results of the measurement may be converted to percent relative humidity by using the following expression:
hum = -6.0+125.0/65536.0*rval
A humidity measurement will always return XXXXXX10 in the LSB field -> Status bit = 1 -> marking a Humidity measurement data.
function read_hum() write_Si_Reg(dev_addr, RHumidityHoldCmd) tmr.delay(10000) read_Si_Reg(dev_addr) hum = -6.0+125.0/65536.0*rval print("\nStatus : "..status) print("Humidity : "..string.format("%.2f",hum).."%") end
5. Measuring Temperature
Each time a relative humidity measurement is made a temperature measurement is also made for the purposes of temperature compensation of the relative humidity measurement. If the temperature value is required, it can be read using command 0xE0; this avoids having to perform a second temperature measurement. The measure temperature commands 0xE3 and 0xF3 will perform a temperature measurement and return the measurement value, command 0xE0 does not perform a measurement but returns the temperature value measured during the relative humidity measurement. The checksum output is not available with the 0xE0 command.
The results of the temperature measurement may be converted to temperature in degrees Celsius (°C) using the following expression:
temp = -46.85+175.72/65536.0*rval
A temperature measurement will always return XXXXXX00 in the LSB field - Status bit = 0 -> marking a Temperature measurement data.
function read_temp() write_Si_Reg(dev_addr, TempHoldCmd) read_Si_Reg(dev_addr) temp = -46.85+175.72/65536.0*rval print("Status : "..status) print("Temperature : "..string.format("%.2f",temp).."C") end
If you remember my article about PCF8563 Real Time Clock this one was a looong avaited MailBox hit. Actually I didn't expect it to show anymore after so much time but miracles happening sometime:) The DS3231 is a extremely accurate I2C real-time clock (RTC) with an integrated temperature-compensated crystal oscillator (TCXO) and crystal. The device incorporates a battery input, and maintains accurate timekeeping when main power to the device is interrupted. The integration of the crystal resonator enhances the long-term accuracy of the device as well as reduces the piece-part count in a manufacturing line.
The RTC maintains seconds, minutes, hours, day, date,month, and year information. The date at the end of the month is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator.
Two programmable time-of-day alarms and a programmable square-wave output are provided. Address and data are transferred seriallythrough an I2C bidirectional bus.
A precision temperature-compensated voltage reference and comparator circuit monitors the status of VCC to detect power failures, to provide a reset output, and to automatically switch to the backup supply when necessary. Additionally, the RST pin is monitored as a pushbutton input for generating a μP reset.
DS3231 Typical Operating Circuit
FEATURES :
Highly Accurate RTC Completely Manages All Timekeeping Functions
• Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year, with Leap-Year Compensation Valid Up to 2100 • Accuracy ±2ppm from 0°C to +40°C • Accuracy ±3.5ppm from -40°C to +85°C • Digital Temp Sensor Output: ±3°C Accuracy • Register for Aging Trim • Active-Low RST Output/Pushbutton Reset Debounce Input • Two Time-of-Day Alarms • Programmable Square-Wave Output Signal
Simple Serial Interface Connects to Most Microcontrollers
• Fast (400kHz) I2C Interface
Battery-Backup Input for Continuous Timekeeping
• Low Power Operation Extends Battery-Backup Run Time • 3.3V Operation
Operating Temperature Ranges: Commercial (0°C to +70°C) and Industrial (-40°C to +85°C)
As you can see from the pictures above, a nice compact module, with backup battery holder on the back (CR2032). Also you can find on the same module sharing the I2C bus a 24C32N EEPROM ( 32k - 4096 x 8) , totally independent from the RTC circuit. A nice addon for a possible WIFI Datalogger system, what do you think about? :)
32k might sound a small amount of data storage but depending on your application requests might be more than enough for collecting 6 moths or a year data, even more. As I know already from your requests that this subject is of big interest, we will elaborate more about this one in the next article, for now let's go back to our fancy RTC :)
Clock and Calendar - Theory of operation
The time and calendar information is obtained by reading the
appropriate register bytes. The time and calendar data are set or
initialized by writing the appropriate register bytes. The contents of
the time and calendar registers are in the binary-coded decimal (BCD)
format.
The DS3231 can be run in either 12-hour or 24-hour mode. Bit
6 of the hours register is defined as the 12- or 24-hour mode select
bit. When high, the 12-hour mode is selected. In the 12-hour mode, bit 5
is the AM/PM bit with logic-high being PM. In the 24-hour mode, bit 5
is the 20-hour bit (20–23 hours).
The century bit (bit 7 of the month register) is toggled when the years register overflows from 99 to 00.
The
day-of-week register increments at midnight. Values that correspond to
the day of week are user-defined but must be sequential (i.e., if 1
equals Sunday, then 2 equals Monday, and so on). Illogical time and date
entries result in undefined operation.
When reading or writing the
time and date registers, secondary (user) buffers are used to prevent
errors when the internal registers update. When reading the time and
date registers, the user buffers are synchronized to the internal
registers on any START and when the register pointer rolls over to zero.
The time information is read from these secondary registers, while the
clock continues to run. This eliminates the need to reread the registers in case the main registers update during a read.
The
countdown chain is reset whenever the seconds register is written.
Write transfers occur on the acknowledge from the DS3231. Once the
countdown chain is reset, to avoid rollover issues the remaining time
and date registers must be written within 1 second. The 1Hz
square-wave output, if enabled, transitions high 500ms after the seconds
data transfer, provided the oscillator is already running.
USB adapter (take a look on Part 1 for details how to connect them together)
DS3231 Module from above
For programming and uploading the driver and the software we will continue to use the LuaUploader as before.
Driver implementation As DS3231 has a I2C compatible
compatible interface, driver building it following more or less the
same process as before for I2C devices.
1. Data conversion functions:
1.1 Decimal to BCD: function decToBcd(val) local d = string.format("%d",tonumber(val / 10)) local d1 = tonumber(d*10) local d2 = val - d1 return tonumber(d*16+d2) end
1.2 BCD to Decimal:
function bcdToDec(val) local hl=bit.rshift(val, 4) local hh=bit.band(val,0xf) local hr = string.format("%d%d", hl, hh) return string.format("%d%d", hl, hh) end 2. Init I2C bus/interface:
address = 0x51, -- A2, A1, A0 = 0 id = 0 init = function (self, sda, scl) self.id = 0 i2c.setup(self.id, sda, scl, i2c.SLOW) end
For testing, pack it together and save the code on ESP as 'ds3231.lua', restart ESP and run:
-- Set Initial Time and Date require('ds3231') -- call for new created DS3231 Module Driver sda, scl = 2, 1 -- declare your I2C interface PIN's ds3231:init(sda, scl) -- initialize I2C Bus ds3231:setTime(5,08,12,3,6,04,15) -- setTime(s,min,hour,weekday,day,month, year) -- get Time and Date require('ds3231') sda, scl = 2, 1 ds3231:init(sda, scl) s, m, h, d, dt, mn, y = ds3231:readTime() =string.format("%s - %s/%s/20%s",d, dt, mn, y) =string.format(" %s:%s:%s", h, m, s)
First run test
5. Read Time & Date - Print on LCD require('st7032i') sda, scl = 2, 1 st7032i:init_i2c(sda, scl) st7032i:init_LCD()
Time_LCD = function() s, m, h, d, dt, mn, y = ds3231:readTime() date = string.format("%s",dt).."/"..string.format("%s",mn).."/"..string.format("20%s",y) st7032i:lcd_print(3,1,date) time = string.format("%s",h)..":"..string.format("%s",m)..":"..string.format("%s",s) st7032i:lcd_print(4,2,time) end
tmr.alarm(0, 1000, 1, function() Time_LCD() end) -- set call Time_LCD function Timer
After testing the ESP8266 Internal ADC I think it's time to see also a higher resolution ADC at work. For this project we will use Microchip MCP3421 I2C ADC.
The MCP3421 is a single
channel, low-noise, high accuracy delta-sigma A/D converter with
differential inputs and up to 18 bits of resolution in a small SOT-23-6
package.The on-board precision 2.048V reference voltage enables an
input range of ±2.048V differentially. The device uses a two-wire I2C
compatible serial interface and operates from a single power supply
ranging from 2.7V to 5.5V.
This device has an onboard programmable gain amplifier (PGA). User can
select the PGA gain of x1, x2, x4, or x8 before the analog-to-digital
conversion takes place. This allows the MCP3421 device to convert a
smaller input signal with high resolution.
The device has two possible to configure conversion
modes:
Continuous mode
One-Shot mode.
In One-Shot mode, the
device enters a low current standby mode automatically after one
conversion. This reduces current consumption greatly during idle
periods. Very goob for low power battery powered applications.
Because of the high interest and the number of requests raised by the CBDB project in the next weeks we will run small batches of CBDB based devboard PCBs. The main purpose of the CBDB board was for local training and drivers development but if any new one interested please express your wishes at: tech at esp8266-projects.com.
It will be nothing fancy, just CBDB Board + some extra goodies on a standard 2 side factory made PCB that can help you to connect in minutes a new module and start programming. A nice I2C Dev Board, KISS concept at its plenitude :). A related Article will follow as soon as the first ones will hit the MailBox.
As MCP3421 has a I2C compatible compatible interface, driver building it
following more or less the same process as before for I2C devices. Few important consideration about MCP3421:
The MCP3421 has an
8-bit wide configuration register to select for: PGA gain, conversion
rate, and conversion mode. This register allows the user to change the
operating condition of the device and check the status of the device
operation. The user can rewrite the configuration byte any time during
the device operation.
The MCP3421 device accepts a fully differential analog input signal which is connected on the VIN+ and VINinput pins. The differential voltage that is converted is defined by VIN = (VIN+ - VIN-) where VIN+ is the voltage applied at the VIN+ pin and VIN- is the voltage applied at the VIN- pin. The input signal level is amplified by the programmable gain amplifier (PGA) before the conversion. The digital output code produced by the MCP3421 is a function of PGA gain, input signal, and internal reference voltage. In a fixed setting, the digital output code is proportional to the voltage difference between the two analog inputs.
The output data format is a binary two’s complement.
With this code scheme, the MSB can be considered a sign indicator. When the MSB is a logic ‘0’, it indicates a positive value. When the MSB is a logic ‘1’, it indicates a negative value. The following is an example of the output code:
for a negative full-scale input voltage: 100...000
for a zero differential input voltage: 000...000
for a positive full-scale input voltage: 011...111.
The MSB is always transmitted first through the serial port. The number of data bits for each conversion is 18, 16, 14, or 12 bits depending on the conversion mode selection. LSB size vs. conversion mode set : Bit Resolutions LSB (V) 12 bits 1 mV 14 bits 250 μV 16 bits 62.5 μV 18 bits 15.625 μV
For programming and uploading the driver and the software we will continue to use the LuaUploader as before.
1. Init I2C bus/interface init = function (self, sda, scl) i2c.setup(0x0, sda, scl, i2c.SLOW) end
2. Write ADC Register Function
write_ADC_config = function ( self, dev_addr, set) i2c.start(0x0) i2c.address(0x0, dev_addr ,i2c.TRANSMITTER) i2c.write(0x0,set) i2c.stop(0x0) end
3. READ ADC Function - 12, 14, or 16 bit-mode, 0-2.048V Range
read_ADC_data = function (self,dev_addr) i2c.start(0x0) i2c.address(0x0, dev_addr,i2c.RECEIVER) c = i2c.read(0x0,3) i2c.stop(0x0) vadc = (bit.lshift(string.byte(c, 1), 8) + string.byte(c, 2)) return vadc end
For testing, pack it together and save the code on ESP as 'mcp3421.lua', restart ESP and run:
require('mcp3421') -- call for new created MCP3421 Module Driver sda=2 --GPIO4 scl=1 --GPIO5 mcp3421:init(sda, scl) -- init I2C mcp3421:write_ADC_config(0x68, 0x10) -- Write Register config: 12Bit/CCV/PGA = 1V/V adc_val = mcp3421:read_ADC_data(0x68) -- Read ADC Data
print("ADC Value : "..adc_val)
lsb=1 -- 12 bit -> LSB = 1mA
vts = (adc_val * l1)/1000*4.3043 --calibrate based on your power supply, Vref and divider print("\nValue = " ..adc_val.." \nVolts = "..string.format("%g",vts).." mV") print("\nValue = " ..adc_val.." \nVolts = "..string.format("%.4f",vts).." mV")
MCP3421 ADC - First test
First Test Video - Noisy environment - Live Bus voltage:
Filtered clean source voltage measurement :
4. Read ADC and Print values on LCD read_ADC_LCD1 = function() adc_val = mcp3421:read_ADC_data(0x68) l1=1 -- 12 bit --l1=0.0625 -- 16 bit val = (adc_val * l1)/1000*4.3043 print(" ReadADC : "..val) val = string.format("%g",val) st7032i:lcd_print(0,2,adc_val) st7032i:lcd_print(9,2,val) end
For testing, pack it together and save the code on ESP as 'mcp3421.lua', restart ESP and run:
