In countries where the climatic conditions are harsh, after a snowfall or freezing cold, how many times have we found shelter in spreading salt on the stairs and on the ramp leading to the garage?
In mountains, where winters are particularly harsh, people have paved stretches become dangerous by ice or snow and often it needs an automated system that avoids task of get up early to make accessible the garage.
Would it be possible to have garage ramps or outside stairs always free from ice without having the worry of activating the switch for snow melting cables?
Flint is the simply, compactness and low cost solution.
Snow melt cables have large power consumption, Flint can perform an automatic control to avoid waste of power. It detects a capacity change, then verify the presence of ice through temperature sensor and, if both conditions are true, it sends an high signal to activate the snow melting cables. For temperature above zero, any detected capacity changes are ignored.
Step 1: COMPONENTS NEEDED
- Arduino Uno
- Telecontrolli Ice Sensor
- 2xLED diodes
- LM393n Comparator
- Capacitors: 2.2 uF, 100 nF
- Resistive Trimmer 100KOhm
- Resistors: 1MOhm, 2x330 Ohm, 220KOhm, 1KOhm
- Connectors sword for giving stability when PCB is mounted on Arduino
- USB type-A Plug
- 5V 1A power bank
- 12V Power supply
Step 2: ICE SENSOR
Ice Sensor is a Telecontrolli sample and it will be soon ready for sale. Keep on eye on Telecontrolli web site http://telecontrolli.com/
On sensitive surface, ice capacitive sensor has a nominal capacity value between 245 pF and 250 pF (+/- 10%) and it uses the dielectric constant change, and thus of the capacity (C = ε A / d), when an external body touches the surface. In particular it is sensible to ice. It integrates a thermistor (NTC), that reads external temperature, and a heater resistor (12V operating) that's used to dry the sensor after a detection. Flint doesn’t integrate last functionality, but this article proposes a circuit with NPN BC337 transistor to heat ceramic substrate.
Step 3: FLINT SCHEMATIC
In the analog comparator LM393N, when the non-inverting input voltage is greater than the inverting terminal, the output is high, viceversa on the inputs, the output is low. A capacity variation changes the voltage on the positive terminal, checking the condition V+<V- and comparator has a low output that put LED in conduction mode. Through 220KOhm resistor the non-inverting terminal becomes more sensitive to the impedance sensor changes, while the trimmer adjustment moves the inversion state close to the trigger threshold comparator. A1 analog input Arduino reads the output comparator and, through a software control, Arduino sends a high/low value digital output to turn on/off green LED. The NTC reading is made through a 1KOhm resistor.
Step 4: FUTURE DEVELOPMENTS
It can be mounted a circuit to monitor the capacity changes in precense/absence of ice and to draw real time temperature trend. Using the NPN BC337 transistor with Ic = 800mA and VCE = 40V, connencted through heater to a power supply of 12V we have a know collector current, so power P=3.43W. In this way, by activating the heater you can calculate mass umidity on the sensor through a software implementation or simply you can clean the frozen conductor after a detection. The heater activation can be made through a switch.
Step 5: THE SKETCH
Below there are the Flint sketch and the future development sketch powered by Nicola Campanale (Electronics Engineer):
Step 6: ACKOWLEDGEMENTS
- Mr. Francesco Verolino (Telecontrolli CEO) for giving me the opportunity to test their products
- Mr. Giovanni Caruso (Telecontrolli Process Enginnering Chief), Mr. Raffaele Basile (Telecontrolli Test Enginnering Chief) for technical support
- Mrs. Paola De Amici (Telecontrolli Visual Designer) for communication pratical tips