NEWBORN INCUBATOR

GLOSSARY

Temperature:                                        

A magnitude that measures the thermal level or the heat that a body possesses.

PDI Control:                                           
(Proportional-integral-derivative control action), is a control mechanism that through a feedback loop allows to regulate speed, temperature, pressure and flow among other variables of a process in general.
P Control:                                              

(Proportional control action), gives a controller output that is proportional to the error, ie: u (t) = KP.e (t).

PD Control:                                            

(Proportional-derivative control action), this action has a forecast character, which makes the control action faster, although it has the important disadvantage that amplifies the noise signals and can cause saturation in the actuator. The derivative control action is never used by itself, because it is only effective during transient periods.

Humidity:                                              

It is the water vapor contained in the atmosphere.

DEVELOP 

A newborn incubator is a medical device used mainly to generate an ideal environment in which different variables important for the development of newborns are controlled.
The incubator consists of an aseptic chamber for premature babies, its air circulation system in the incubator is designed to give the premature baby an optimal atmospheric pressure, due to the careful control of the temperature and the supply of moisture and oxygen.

 Figure 1. Parts of an newborn incubator

In the incubators that work by thermal convection, the heat generated by the resistance system is transferred to a fluid in this case, which circulates in the incubation chamber, transferring the heat to the samples; The efficiency of this process depends on its flow patterns. In general, the air enters the incubator from the bottom and is heated in a compartment,
from which it flows to the incubation chamber, following uniform flow patterns, to finally go outside through a path located in the upper part of the incubator.

The basic equation that explains the behavior is:

q = hA (TW - Tθ)

where:
q = amount of heat transferred by convection
h = heat transfer convection coefficient
A = area through which the heat transfer is carried out
TW = temperature on the surface of the resistance

Tθ = fluid temperature
Some incubators also have fans that circulate the air, so the convection process is forced. In the diagram presented below, three design criteria used in the incubators are shown: thermal conduction, natural convection and forced convection.

Characteristics:

•Generally the cover is of simple or double acrylic that prevents the losses by radiation and facilitates the continuous observation of the patient.   

• It has different orifices that allow manipulation of the newborn and the entrance of ventilation equipment, monitoring and venous lines for the administration of medicines and parenteral nutrition.

• Modern neonatal incubators have electronic sensors and light screens that allow to continuously know the temperature and humidity ranges.

• They can also count on included scales that avoid excessive manipulation of the patient and filters to purify the air. It is also used in heavier children cribs with radiant heat sources.

Recommendations for use
1. Do not use an incubator in the presence of flammable or combustible materials, because inside the equipment there are components that in operation could act as sources of ignition.
2. Avoid spilling acid solutions inside the incubator. These deteriorate the internal materials of the incubation chamber. Try to handle substances whose pH is as neutral as possible. Avoid incubating substances that generate corrosive fumes.
3. Avoid placing containers on the lower cover that protects the resistive heating elements.
4. Use personal protection items when using the incubator: safety glasses, gloves, tweezers to place and remove containers.
5. Avoid standing in front of an incubator with the door open. Some substances emit fumes or vapors not recommended for breathing.
6. Calibrate the incubator at the installation site to verify its uniformity and stability.
7. Verify the operating temperature of the incubator in morning and evening hours, with certified instruments: thermometer, thermo pair, etc.
8. Record each nonconformity detected in the incubator log. Explain if corrective actions were taken.
9. Verify that the temperature of the incubator does not vary more than one degree centigrade (+/- 1 ° C).
10. Add a non-volatile microbial inhibitor, if a container with water is required to be installed in the incubator to maintain a certain amount of moisture.
Daily maintenance:
The daily care includes the attention of the accesses and the hermetic closures, as well as the ventilators and the anesthesia apparatuses, the incubator has to be checked completely twice a year, and the operation must be verified after each cleaning Observe if:
• It is heated to a fixed temperature and is capable of maintaining it.
• Excessive temperature alarm operates at the corresponding level.
• All quadrants give correct values.

RESULTS

For the elaboration of the incubator an air inlet fan and an air outlet fan were used to regulate the air circulation in the incubator, a sensor was also implemented to measure the relative humidity inside the incubator and another to measure temperature. For the increase and decrease of temperature and humidity, an analogous proportional power control was performed for the ambient and inversion resistance; characterizing each sensor so that the error of these is minimal. It should not be stressed that the model had three alarms, the first indicates if the dome is not fully closed, the second alarm is related to the temperature, whether it was below or above the set value and the last one is concerned to the percentage of humidity, also if it was below or above the established value.
In the design of the power stage of the incubator one of the parameters that greatly affected was the caliber of the wire used for the connection, this caused that the insulation of all was carbonized causing in turn that the heat transfer melted the internal contacts of the protoboard and short circuit between them which in the end results in an explosion of the circuit.
Another point that should be considered is the location of the sensors since this could influence the data collection. Since if they were near where the resistors were, they would have a very high value, but if they are located in the center of the dome, a measure could be obtained with a certain accuracy.

Figure 2. Design of newborn incubator

Figure 3. Disposition of  the parts of newborn incubator

Figure 4. Side view of design of  newborn incubator

CONCLUSIONS

In the development of the power stage of the incubator there are several recommendations for future generations, the Amperage that flows is enough and therefore a suitable wire gauge is needed to support it, in our case the circuit cables got too hot what caused that the rubber that covered them melted, it happened the same with the plastic material of the breadboard, it is so that at a certain moment there was the union of all the cables of the bt137 cables which caused a short circuit and the subsequent burst of the circuit.

In the implemented circuit a control was used for both parameters (temperature and humidity) could be controlled and varied in an analogous way, in spite of this, it was decided to leave the constant temperature and control the percentage of relative humidity of the incubator, in a moment to cause of the movement. the submersible resistance did not ignite at the moment that it had to, the error was solved but the capacity of control.