Neonatal incubator

Neonatal Closed incubator

The design of this equipment is about control temperature and humidity to idealy keep babies here when they need it, so our deing contemplate the control by two modes: of humidity through HS 1100 sensor and of temperature about lm35 sensor.  Generally this machine can not get wet on the dome and it must have a system to flow air fresh but isolated of external environment.   the idea is create a new perfect environment to complete the development and growth of babies.

Image 1. Sensor Lm35 to control temperature in neonatal closed incubator.

Image 2. Sensor of humidity HS1101.

The caracterization of humidity sensor is realized by astable configuration of 555 timer.  So, this sensor have a behavior as a capacitor and then when it detect changes of humidity, in 555 astable circuit, the frecuency generated by pin 3 is changed too.  According to datasheet of Parllax producer we get this information:

Image 3. Output in frecuency adn voltage of astable circuit with HS1101 sensor and 555 timer-

Image 4. Technical characteristics of HS1101 sensor.

So we decided get the frecuency response of this sensor, and we characterized with the next circuit the frecuency response vs relative humidity:

Image 5. Astable configuration woth HS1101 sensor 

Image 6. Parametrization of sensor

Image 7.  Lineal regression to set HS1101 sensor.

So, with the equation of the line, we get that:

And with this, only we get to design a proporcional control to keep himidity in a specific value about needs of babies:

Image 8. Table with corresponding humidty to age weeks of neonates.

The arduino code to probe that HS1101 is function is the next one:

Image 9. Arduino code to probe sensor of humidity.

Now, the temperature sensor ir more simple to control, because according to datasheet it send a voltage response lineal about temperature: it sensibility is 10mV/°C and it have a range of -50°C to +150°C

Image 10. Technical characteristics of LM35 sensor

Image 11. Lineal response of temperature sensor.

So the code to probe this sensor is simple too, because we get the voltatae response, and we convert analog voltage to temperature with the sensibility of this dispositive.

Image 12. Arduino code to probe temperature sensor.

The neonatal incubator is composed by:

1. Control Panel.
2. Fixed bearing.
3. Balance Kit.
4. Illumination or dispositive to phototherapy.
5. Support
6. Bracket.
7. Suero support.
8. Auxuliar plugs
9. Oxigen system.
10. Venilator/respirator








But our design only is composed by the control panel, the dome, ventilator systems, and calefaction/humification system.

Image 13. Material list

With the temperature and humidity sensor, we control the temperature by convexion and generate by a heat resistance to 110V AC with a power circuit with thyristor SCR106D where is send a PWM based in a Control proportional.
So there are two modes in this incubator: Temperature control and Humidity control.
In temperature control, we go to apply a porportional control to get temperature in a range of 33 to 37.5°C and the humidity is constant, but it was selected previously in any value beetween 50-90% of HR. 
And control Humidity is similar: the range of control is 40-95% HR according to before table and the temperature keep constant in 37.5°C.

Image 14. Selection of HR to control Humidity mode.

Image 15.  Power circuit to control heat resistance and water heat resistance.

Image 16. Power circuit to send PWM to control blowers.

The idea of proportional control is keep a gain between an input signal and error signal (adjusting the gain), it reduce reponse time of any plant (in this incubator system, the relation between temperature measure and temperature that was selected or should arrive, and its the same to humidity).

Image 17.  Diagram Blocks of proportional control 

Image 18.  Equations to Control P in Neonatal closed incubator

Finally the arduino code can downloaded of this link: Here is the Proportional code to temperature mode control in this incubator. https://drive.google.com/open?id=1wmzAdAZ0l3S4vWC0gEhohfpxilXOwlXo