Incubators are devices designed to produce the appropriate environmental conditions specific to each patient and used during the care of high-risk infants, since when the newborn is subject to uncontrolled environmental conditions, its Body temperature tends to descend because of the immaturity of your nervous system .
Prototype Design
A prototype neonatal incubator was performed that must meet the following requirements:
Humidity control using HS 1100 sensor
Temperature control
Friendly user interface
The dome of the machine can not get wet
On-Off control can NOT be use
Alarms: at least 3 according to the manual of the machine that you used as reference (related with the control or how the machine works)
Math develop of the design (including sensors parametrization)
Materials used
HS1100 sensor
Based on a unique capacitive cell, these relative humidity sensors are designed for high volume, cost sensitive applications such as office automation, automotive cabin air control, home appliances, and industrial process control systems. They are also useful in all applications where humidity compensation is needed.
LM35
is a temperature sensor with a calibrated accuracy of 1 °c. Its measuring range ranges from-55 °c to 150 °c. The output is linear and each degree Celcius equals 10 mv, therefore:
150 °c = 1500 mv -55 °c =-550 mV1 operates from 4v to 30v.
Its most relevant features are:
is calibrated directly in degrees Celsius.
The output voltage is proportional to the temperature.
has a guaranteed precision of 0.5 ° C to 25 °c.
Low output impedance.
Low Feed current (60 μA).
Low cost.
Arduino Uno
The Arduino UNO is a widely used open-source microcontroller board based on the ATmega328P microcontroller and developed by Arduino.cc.The board is equipped with sets of digital and analog input/output (I/O) pins that may be interfaced to various expansion boards (shields) and other circuits.[1] The board features 14 Digital pins and 6 Analog pins. It is programmable with the Arduino IDE (Integrated Development Environment) via a type B USB cable.[4] It can be powered by a USB cable or by an external 9 volt battery, though it accepts voltages between 7 and 20 volts. Technical details:
Microcontroller: ATmega328P
Operating Voltage: 5v
Input Voltage: 7-20v
Digital I/O Pins: 14 (of which 6 provide PWM output)
Analog Input Pins: 6
DC Current per I/O Pin: 20 mA
DC Current for 3.3V Pin: 50 mA
Flash Memory: 32 KB of which 0.5 KB used by bootloader
SRAM: 2 KB
EEPROM: 1 KB
LCD
A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in colour or monochrome. LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden, such as preset words, digits, and 7-segment displays, as in a digital clock. They use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements.
Procedure performed
The incubator is designed in wood for the bases where the whole system of heating and Humidification, the dome was made with acrylic.
For the heating system is used a heating resistance to 120 V with a fan, for the humidification system is used an immersion resistance also to 120 V with an exhaust fan
A HS1101 humidity sensor is used to measure humidity and a LM35 sensor to measure temperature.
HUMIDITY
RELATIVE HUMIDITY SENSOR HS 1101
Based on a unique capacitive cell
This circuit is the typical astable design for 555. The HS1100/HS1101, used as variable capacitor, As the capacitance varies, the frequency
Typical Characteristics for Frequency Output Circuits, According to the manufacturer
It was possible to obtain the following equation with the aim of obtaining the humidity with respect to the variation of frequency
The implemented algorithm gets the frequency and this in turn makes the conversion to relative humidity
The designed incubator has three ranges of variation in humidity which are selected by means of a dip switch the ranges are: < 60, 60%-70%, 70%-80%.
humedad 70-80
if (hr > 70 && hr < 80)
{
analogWrite(digPin, 20);
analogWrite(ven, 20);
}
if (hr > 80)
{
analogWrite(digPin, 100);
analogWrite(ven, 127);
}
if (hr < 70)
{
analogWrite(digPin, 15);
analogWrite(ven, 15);
}
humedad 60-70
if (hr > 65 && hr < 70)
{
analogWrite(digPin, 90);
analogWrite(ven, 90); //tem
}
if (hr > 70)
{
analogWrite(digPin, 190);
analogWrite(ven, 190);
}
if (hr < 65)
{
analogWrite(digPin, 20);
analogWrite(ven, 20);
}
humedad <60
if (hr > 59)
{
analogWrite(digPin, 255);
analogWrite(ven, 255);
}
if (hr < 58)
{
analogWrite(digPin, 127);
analogWrite(ven, 70);
}
TEMPERATURE
The LM35 series are precision integrated-circuit temperature devices with an output voltage linearly proportional to the Centigrade temperature.
Code implemented to perform voltage-to-temperature conversion
temperatura 36-37
if (tem > 36 && tem <37 )
{
analogWrite(digPin, 190);
analogWrite(ven, 190); //tem
}
if (tem > 37)
{
analogWrite(digPin, 255);
analogWrite(ven, 255);
}
if (tem < 36.2)
{
analogWrite(digPin, 40);
analogWrite(ven, 20);
}
temperatua 35-36
if (tem > 35 && tem <36 )
{
analogWrite(digPin, 200);
analogWrite(ven, 200); //tem
}
if (tem > 36)
{
analogWrite(digPin, 255);
analogWrite(ven, 255);
}
if (tem < 35.2)
{
analogWrite(digPin, 40);
analogWrite(ven, 20);
}
temperatura 33-34
if (tem > 34 && tem <35.2 )
{
analogWrite(digPin, 220);
analogWrite(ven, 220); //tem
}
if (tem > 35.2)
{
analogWrite(digPin, 255);
analogWrite(ven, 255);
}
if (tem < 34.2)
{
analogWrite(digPin, 20);
analogWrite(ven, 20);
}
The main idea is to vary the PWM (speed) of the fan and the extractor in such a way that if the temperature is higher than the desired the fan and the extractor refrigerate the faster, on the contrary if the temperature is below the fan speed and the ext Ractor must be low generating a temperature increase
ALARMS
For alarms, 2 red LEDs and a buzzer were used
Lower Alarm: Activates when the temperature or humidity is below the desired range by the user
Upper alarm: This alarm was activated when the temperature or humidity is above the desired range by the user
Water level alarm: This was activated when the water level of the humidification system was very low
Electrical diagram to detect low water level
Comments