Building an Arduino shield to control sockets and cooling fan
Purpose:
1.The direct use of solar power while it is provided by the solar-panels.
Switchable plug-in sockets are used for power users like electric boiler, battery chargers, heaters or other appliances. The boiler socket is hard wired. Others use Remote Controlled sockets for which a small 433MHz transmitter is used.
2.To switch a cooling fan "on" when the temperature of the inverter rises above a certain level. (to prevent the inverter from powering down)
The internal data of the inverter is accessed via a MAX485 module at the top. (with the green connection block)
It is "plugged in" on digital data ports 3, 4,5 and 6 at the left side.
The orange and white (twisted) RS485 A and B wires, coming from the green connection block, are connected to RJ45 jack pin 4 and 5 of the inverter.
VCC of the MAX module (red wire) is plugged on a pin sticking through the shield into the 3,3 V outlet of the Arduino.
GND of the MAX module (black wire) is likewise connected to the Arduino's GND close to the 3.3V pin.
The shield contains 4 circuits which sometimes share connections:
1. Digital OUTPUT D8 controls the fan:
When the temperature of the inverter gets to high 5V is put on a relay module The relay module provides the fan with the same power feeding the Arduino. (A 230V > 12 V power adaptor.)
The relay module uses the 5V and GND from the Arduino as illustrated:
2. Digital OUTPUT 5 V to switch the hardwired boiler socket
The socket part in which the boiler is plugged, is controlled by a relay. This relay switches the 230V "on" when it is powered with 5V from the Arduino. In our case we let the digital output D8 switch the negative output to the relay of the boiler socket. We do this as illustrated with a transistor. The (blue) LED on the Arduino shield, as well a LED on the boiler socket, indicate "the power on" situation.
3. Digital INPUT D10 and D11 from mode switch
A 3-way switch lets u choose from different modes:
switch up - power always on the boiler socket
switch down - power boiler socket off
switch centre position - boiler socket regulated by the power value given by the inverter.
In the first case 5V is put on pin 11 and in the second case 5V is put on pin 10 both pins in INPUT mode, In the 3th case pin 10 and 11 are 0V .Pull down resistors are used to make 0 really 0.
4. Digital OUTPUT 12 sends the codes for de remote controlled switches to the small 433MHz transmitter. GND and VCC of the transmitter are connected as illustrated.
The print is used "upside down" to facilitate the fixing and connecting of the header pins which stick into the Arduino.
Except for the 3.3V pin and one GND pin (to power the MAX 485 Module) they are bend flat and soldered on. I used an old non working Arduino while assembling the parts. Some of the parts are on the non visible side.
The program listing is from a working setup. It is included as an example. The switching delays and settings are not fully optimized yet.
www.bootprojecten.nl Jeroen Droogh, bootprojecten@gmail.com