THERMOSTAT 2 CLICK
PID: MIKROE-3415 Weight: 30 g
Thermostat 2 click is a general-purpose thermostat Click board™ designed to be used
with any temperature sensor based on the DS1820 sensor design: 3-pin package with
1-Wire® communication interface. The Click board™ is equipped with a 3-pole terminal
and a 3-pin female socket. DS1820 (or compatible) sensor can be connected either
over the terminal or can be installed directly into the socket. The Click board™ also
contains a high-quality relay from Omron, that can be used to open or close an electric
circuit. Despite its small size, it can be used with voltage up to 30VDC/220AC and
current up to 5A.
Thermostat 2 Click is supported by a mikroSDK compliant library, which includes
functions that simplify software development. This Click board™ comes as a fully tested
product, ready to be used on a system equipped with the mikroBUS™ socket.
The Click board™ is equipped with all the necessary elements, required to provide a
reliable operation: it has a varistor across the relay output contacts, preventing
excessive voltage transients, it has a flyback diode for the backEMF generated within
the relay coil, and a durable mechanical relay, that can withstand up to 20,000,000
mechanical cycles (no load connected). These features allow Thermostat 2 click to be
used for a wide range of applications that have to be thermally controlled: various home
appliances, air conditioners, cooling fans, small heaters, etc.
DO NOT TOUCH THE BOARD WHILE HIGH VOLTAGE IS APPLIED!
Note: The Click board™ is to be used by trained personnel only while the high voltage is
applied. A special care should be taken when working with hazardous voltage levels.
HOW DOES IT WORK?
Thermostat 2 Click board™ is designed without the main IC; it allows an externally
connected thermal sensor to be used, instead. It can be interfaced with the DS1820
compatible sensor which uses 1-Wire® communication. The Click board™ is equipped
with a 3-pin female socket, which can be used to install the DS1820 compatible sensor
in TO-92 casing, onboard. There is also a 3-pole screw terminal, that can be used if the
sensor needs to be installed on a remote location, i.e. onto a heating component. The
screw-terminal shares its lines with the socket.
The 1-Wire® communication with the host MCU is performed over the PWM pin of the
mikroBUS™. Depending on the temperature information obtained over the 1-Wire®
interface, the host MCU can take the necessary action: it can either open or close
contacts of the relay.
The Click board™ uses the G6D series PCB power relay, from Omron. This quality relay
can withstand an amazingly large number of mechanical cycles, with no load
connected. However, when there is a significant load connected at its output, microelectric arcs cause the contacts to wear over time. With the maximum load current of
5A, it can sustain up to 70,000 cycles. Its contacts are made of silver alloy, yielding
exceptional ON resistance of only 100mΩ (max).
The relay is activated by a magnetic field, generated in a built-in coil on the low-voltage
side. The coil is activated by the host MCU. The voltage for the coil activation is 5V,
while the current through the coil is 40mA. The MCU is not able to drive the coil directly,
therefore an NPN transistor had to be added. Its base is controlled by the host MCU,
allowing the coil to drain enough current from the 5V mikroBUS™ power rail. The base
of the transistor is routed to the CS pin of the Click board™. The transistor packs two
biasing resistors in the same casing, so it can be directly used on the MCU pin, without
external biasing resistors. A red color LED, labeled as ACTIVE is used to indicate that
the transistor is in an open state and that the current is running through the relay coil.
When the current through a coil (or any other inductor) is suddenly changed, the
backEMF will be generated, opposing the changes of the current. This can sometimes
lead to damage to the control circuit: in this case, the transistor will become inversely
polarized. To prevent this from happening, a flyback diode is added across the coil.
During the normal operation, this diode does not conduct any current. However, when
the coil is switched OFF, the inverse polarization will cause the current to pass through
this diode with minimum resistance. This prevents inverse (flyback) voltage from
building up, so the transistor remains safe.
Contacts at the output may be connected to a higher voltage and larger current may run
through. To prevent high voltage transients in this case, a flyback diode is not a viable
option. Therefore, Thermostat 2 click uses a varistor (VDR). This component rapidly
drops its resistance as the voltage rises above its rated clamping voltage. The
excessive voltage transient will pass through the VDR since it will become a current
path with the least resistance. During the normal operation, while the voltage stays
below the rated clamping voltage, VDR has a very high resistance, so the current runs
through the electrical circuit, instead.
The operating voltage of the Click board™ can be selected by the VCC SEL jumper.
This jumper allows selecting either 3.3V or 5V from the mikroBUS™. The selected
voltage will be applied to the VCC pin of the connected DS1820 sensor.
SPECIFICATIONS
Type
Relay
Applications
Thermostat 2 click can be used for a wide range of applications
that have to be thermally controlled: various home appliances, air
conditioners, cooling fans, small heaters, etc.
On-board
modules
G6D series PCB power relay, by Omron.
Key Features
Ability to use DS1820 or compatible temperature sensor, both
onboard and connected over a terminal, overvoltage and
backEMF protection, LED indication…
Interface
GPIO,1-Wire
Input Voltage
3.3V,5V
Compatibility
mikroBUS
Click board
size
M (42.9 x 25.4 mm)
PINOUT DIAGRAM
This table shows how the pinout on Thermostat 2 click corresponds to the pinout on
the mikroBUS™ socket (the latter shown in the two middle columns).
Notes
Pin
Pin
NC
1
AN
PWM
16
PWM
NC
2
RST
INT
15
NC
Notes
1-Wire® Data
CS
3
CS
RX
14
NC
NC
4
SCK
TX
13
NC
NC
5
MISO
SCL
12
NC
NC
6
MOSI
SDA
11
NC
Power Supply
3.3V
7
3.3V
5V
10
5V
Ground
GND
8
GND
GND
9
GND
Relay Control
Power Supply
Ground
ONBOARD SETTINGS AND INDICATORS
Label
Name
Default
Description
LD1
PWR
-
Power LED indicator
LD2
ACTIVE
-
Relay status LED, lights up when the relay
is CLOSED
CN1
-
-
External sensor connector
TB1
-
-
Relay output connector
TS1
-
-
Onboard 3-pin sensor connector
JP1
VCC SEL
Left
Power supply voltage selection: left position 3.3V,
right position 5V
SOFTWARE SUPPORT
We provide a library for the Thermostat 2 click on our LibStock page, as well as a
demo application (example), developed using MikroElektronika compilers. The demo
can run on all the main MikroElektronika development boards.
Library Description
The library contains the One Wire functions for full communication from MCU to one of
the DS18k20 sensors. The user also has a relay management function available.
Key functions:
void thermostat2_relay(uint8_t state) - Relay control
void thermostat2_oneWireReset() - One Wire Reset
void thermostat2_oneWireWrite(uint8_t dataIn) - One Wire Write
uint8_t thermostat2_oneWireRead() - One Wire Read
Examples description
The application is composed of the three sections :
System Initialization - Sets CS pin as OUTPUT for control of the relay
Application Initialization - Initialization driver init and sets relay state on OFF
Application Task - Waits for valid user input and executes functions based on set of valid commands
Commands : '+' - Relay ON '-' - Relay OFF 't' - Reads and display Temperature
void applicationTask()
{
float Temperature;
char demoText[50];
uint8_t dataReady_;
char receivedData_;
dataReady_ = UART_Rdy_Ptr( );
if (dataReady_ != 0)
{
receivedData_ = UART_Rd_Ptr( );
switch (receivedData_)
{
case '+' :
{
mikrobus_logWrite(" Relay ON!!! ", _LOG_LINE);
thermostat2_relay(_THERMOSTAT2_RELAY_STATE_ON);
break;
}
case '‐' :
{
mikrobus_logWrite(" Relay OFF!!! ", _LOG_LINE);
thermostat2_relay(_THERMOSTAT2_RELAY_STATE_OFF);
break;
}
case 't' :
{
Temperature = thermostat2_getTemperature();
FloatToStr(Temperature, demoText);
mikrobus_logWrite("Temperature : ", _LOG_TEXT);
mikrobus_logWrite(demoText, _LOG_TEXT);
mikrobus_logWrite(" C ", _LOG_LINE);
break;
}
}
}
}
Additional Functions :
void thermostat2_getTemperature( ) - Reads Temperature (DS18S20)
The full application code, and ready to use projects can be found on our LibStock page.
Other mikroE Libraries used in the example:
One_Wire
UART
Conversions
Additional notes and informations
Depending on the development board you are using, you may need USB UART
click, USB UART 2 click or RS232 click to connect to your PC, for development systems
with no UART to USB interface available on the board. The terminal available in all
MikroElektronika compilers, or any other terminal application of your choice, can be
used to read the message.
MIKROSDK
This click board is supported with mikroSDK - MikroElektronika Software Development
Kit. To ensure proper operation of mikroSDK compliant click board demo applications,
mikroSDK should be downloaded from the LibStock and installed for the compiler you
are using.
For more information about mikroSDK, visit the official page.
https://www.mikroe.com/thermostat‐2‐click//4‐9‐19
