CHAPTER 4 - SGU Repository

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Paulus Gagat Charisma Ar.

CHAPTER 4 – RESULTS AND DISCUSSIONS

In this chapter, we will discuss the result of internal performance test that has been done on the prototype then evaluate it as the improvement of the prototype before continuing with product testing in BPFK. The analysis will refer to data that has been generated before and stated in the previous chapter, that are battery usage analysis, stability &

calibration of generated pressure, and stability of microcontroller program. We do also cost analysis of developing this prototype. In this end of this chapter, researcher also share the update of product testing in BPFK.

Initial Evaluation

The prototype is successfully developed and tested internally with following result:

1. Prototype can be worked properly refer to its setting parameter and requirement from BPFK. In this stage, the process can be continued with product testing in BPFK.

2. Battery capacity is able to use as back-up power the prototype for 2 hours while prototype is running with its highest rating of setting parameter (RR = 30, I:E Ratio

= 1:4). Researcher needs to analysis on the battery usage since there is a gap of voltage between each cells of battery after testing.

3. The pressure generated from the prototype is monitored in the range of allowable pressure. Researcher needs to calculate the stability of pressure generated by calculating the standard deviation and calibrate the pressure sensor with the standard measurement device.

4. The prototype is built as portable product which able to bring with hand, enclosed with an enclosure made from Hot Rolled Steel t:1.0mm sheet. Total weight of the prototype is 10 kgs.

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Figure 4.1. Total weight of the prototype Data Analysis

4.2.1 Battery usage analysis

The performance of the battery is tested on the 2^nd step of performance test when the prototype is operated for 2 hours continuously and no AC power supply is connected.

Summary of battery usage is shown on the table below:

Table 15. Summary of battery usage after 2nd step of performance test No Battery no. Battery Voltage

before (Volt) after (Volt)

1 Cell 1 4.06 V 3.359 V

2 Cell 2 3.98 V 3.353 V

3 Cell 3 4.01 V 3.122 V

4 Cell 4 4.03 V 3.104 V

5 Cell 5 4.04 V 2.866 V

6 Cell 6 3.99 V 2.864 V

Total Voltage in

series 24.11 V 18.668 V

Std. Deviation 3.06% 21.97%

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Refer to the Error! Reference source not found.Table 15, there is such gap of voltage between each cells of battery after done the 2^nd step of performance test. It is calculated the standard deviation for 21.97% with 18.668 V is the remained voltage which is measured from the series connection of 6 pcs battery. Cell 1 which is closest to the positive (+) pole has the highest voltage (3.359 V) while cell 6 has the lowest voltage (2.864 V) is closest to the negative (-) pole. This phenomenon always occur while we charge a series connection of battery and will affect to decrease the battery lifetime. As an evaluation and to anticipate of this phenomenon, we add additional circuit of active balancer energy transfer to balance voltage of each battery. This circuit basically uses IC ETA3000 which utilizes a control scheme with an inductor to shuffle current between two cells of battery until they are balanced. The active balancing board is designed to convert surplus energy from cells with the maximum voltage into cells that are needed to charge. This board is specialized to be used for Lithium cells battery.

Figure 4.2. Typical application circuit of IC ETA3000 (source: datasheet IC ETA3000, www.etasolution.com)

Because the prototype is using 6 cells of battery, therefore we need to use 5 pcs of IC ETA3000. The embedded board for balancing 6 cells of battery is available in the market and can be bought from the online shop.

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Figure 4.3. Embedded board of 6 cells battery active balancing

We do an experiment of using active balancing board with the result as shown in the below table.

Table 16. Summary of battery voltage after added with battery active balancing board No Battery no. Battery Voltage

before (Volt) after (Volt)

1 Cell 1 4.13 V 4.03 V

2 Cell 2 4.08 V 4.02 V

3 Cell 3 4.03 V 4.01 V

4 Cell 4 4.03 V 4.01 V

5 Cell 5 3.97 V 4.00 V

6 Cell 6 3.85 V 3.99 V

Total Voltage in

series 24.09 V 24.06 V

Std. Deviation 9.71% 1.41%

Refer to the summary, we conclude that the active balancing board is working well.

Analysis of the battery also needed to be done on the battery charger system in order to maintain it lifetime performance. Currently, the circuit of battery charger in this prototype uses simple circuit of diode and resistor.

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Figure 4.4. Battery charger circuit

Actual output voltage of the adapter is 24.51 Volt and is used to charge 5 cells of battery which need a constant voltage of 4.2 Volt for each to charge (equal to 25.2 Volt for 6 cells). With this condition, battery can be charged until full capacity. We also can’t control the current flow to the battery with this controller, therefore it may have effect to the battery lifetime, as shown on the battery datasheet below.

Figure 4.5. Charge & cycle life characteristics of NCR18650PF (source: datasheet PanasonicNCR18650PF)

The appropriate battery charger needs to be developed as an evaluation to improvement of this prototype. This part is not in the scope of this research.

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4.2.2 Stability and calibration of generated pressure

During the operation of the prototype, generated peak pressure in every cycle with the same setting parameter ideally should be the same value. The stability of generated pressure can be measured by calculating percentage deviation of peak pressure which is generated in every cycle with its average peak pressure generated during experiment with the same setting parameter.

Table 17. Generated peak pressure during experiment

No Cycle 1 2 3 4 5

1 cycle 1 22.06 21.39 22.72 23.39 24.51

2 cycle 2 22.06 21.72 22.72 24.28 24.27

3 cycle 3 21.50 21.95 22.94 24.16 24.51

4 cycle 4 21.61 21.83 22.61 24.05 24.98

5 cycle 5 20.95 22.28 22.83 24.16 24.34

Average 21.636 21.834 22.764 24.008 24.552

Deviation -3.17% ~ 1.96%

-2.03% ~ 2.04%

-0.68% ~ 0.77%

-2.57% ~ 1.13%

-1.03% ~ 1.87%

Refer to datasheet of MPX5010DP that the accuracy of the output value is ±5.0%, then we can conclude that the generated pressure is still in range of accuracy and has good stability.

The calibration of pressure sensor is done by comparing with standard measurement device, in this case we use FLUKE VT PLUS HF Gas Flow Analyzer as the calibrator which is connected to FLUKE ACCU LUNG Precision Test Lung. We do streaming of the pressure sensor result using Microsoft Excel Data Streamer and note its peak pressure value then compare it with the PIP value which is displayed in the calibrator.

We do 5 experiments during the calibration process with the setting parameter as below:

- Experiment 1 : RR = 12 BPM, I:E Ratio = 1:4 - Experiment 2 : RR = 15 BPM, I:E Ratio = 1:3 - Experiment 3 : RR = 20 BPM, I:E Ratio = 1:2 - Experiment 4 : RR = 30 BPM, I:E Ratio = 1:1 - Experiment 5 : RR = 30 BPM, I:E Ratio = 1:4

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Figure 4. 6. Standard measurement device for calibration Result of the pressure sensor calibration is shown in the below table.

Table 18. Pressure sensor calibration result No Experiment Prototype

(cmH2O)

Calibrator (cmH2O)

Deviation (%)

1 Experiment 1 21.64 22.5 3.97%

2 Experiment 2 21.83 22.6 3.53%

3 Experiment 3 22.76 23.5 3.25%

4 Experiment 4 24.01 24.8 3.29%

5 Experiment 5 24.56 25.3 3.01%

Average 3.41%

Refer to the table above, the average deviation from 5 experiments is 3.41%. We can conclude that the pressure sensor has already measure with the good result compare to the calibration tool.

4.2.3 Stability of microcontroller program

The database of Ti value is created and inputted to the Arduino Due program. This data is used as the reference to generate 8-bit PWM value of actuator speed. The controller also received feedback by calculating the real Ti value which is displayed in the LCD.

Stability of microcontroller program is important to make sure that the device will work

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continuously refer to its setting parameter. By then, we can calculate percentage deviation of real Ti value which is shown in Table 13 and Table 14 with its average real Ti value during experiment with the same setting parameter as follow:

Table 13 : real Ti value = 0.99, 0.98, 0.97, 0.98 : average real Ti value = 0.98

: percentage deviation = 1.02%

Table 14 : Ti value = 0.38, 0.36, 0.4

: average real Ti value = 0.38 : percentage deviation = 5.26%

Refer to the performance test, we conclude that the stability of the microcontroller program has maximum error for 5.26%.

Cost Analysis

The prototype is made from the components and material which available on the common market in Indonesia, which are bought from the online shop. The development cost to manufacture the prototype is listed in the table below:

Table 19. List of material/equipment cost

No Material/Equipment Price Online shop link

1 Adapter 24VDC 10A Rp. 425.000,00 https://tokopedia.link/XlaOWeDdScb 2 PCB double layer

(special order)

Rp. 1.250.000,00 https://tokopedia.link/BQn0w0IeScb

3 Electronic board (refer to guideline)

Rp. 250.000,00

4 Arduino Mega2560 Rp. 115.000,00 https://tokopedia.link/Vik3e7oeScb 5 Arduino Due Rp. 161.500,00 https://tokopedia.link/oAI3jfteScb 6 Boost converter step-up

400W 15A DC-DC

Rp. 90.000,00 https://tokopedia.link/ayqpt7AdScb

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7 LM2596 Adjustable DC-DC module (2 pcs)

Rp. 15.000,00 https://tokopedia.link/NB1sCXdeScb

8 LCD 20x4 Rp. 49.000,00 https://tokopedia.link/9Yyb9yHdScb 9 Pressure sensor

MPX5010DP

Rp. 600.000,00 https://tokopedia.link/kUyvOa7dScb

10 Proximity switch ROKO SN04-N (2 pcs)

Rp. 80.000,00 https://tokopedia.link/0SrugGRdScb

11 Battery NCR18650PF (6 pcs)

Rp. 450.000,00 https://tokopedia.link/2nW9erleScb

12 Battery balancer Rp. 205.000,00 https://shopee.co.id/product/293711904/

6457925625?smtt=0.320502755- 1609664500.3

13 Enclosure box (special order)

Rp. 200.000,00 https://tokopedia.link/Cp6kAQMdScb

14 Acrylic for cover (special order)

Rp. 150.000,00 https://tokopedia.link/dwWoO8UdScb

15 Linear rail guide Rp. 27.500,00 https://tokopedia.link/z3PNgOweScb 16 Wiper Motor 5K Rp. 165.000,00 https://tokopedia.link/SqfqzbAeScb 17 Disposable ambu bag Rp. 170.000,00 https://tokopedia.link/2vcvvLEdScb 18 Bacterial filter Rp. 65.000,00 https://tokopedia.link/12qtWisdScb

Total expense Rp. 4.468.000,00

While below is the table of portable emergency ventilator/resuscitator price which available in the market.

Table 20. Available portable ventilator price in market

No Product type Price Source

1 Portable Ventilator

Allied 200 Rp. 50.000.000,00 https://tokopedia.link/siVQ2a I9Lcb

2 Ventilator BPPT3S- LEN

Rp. 25.000.000,00 https://www.len.co.id/downlo ad/buletin/Bulen31%20(Agu stus%202020).pdf

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3 Portable ventilator DHARCOV-23S

Rp. 78.500.000,00 https://e-

katalog.lkpp.go.id/katalog.pr odukctr/getdetailproductcent er?id=1242519

Product no. 2 and no. 3 are also tested and verified in BPFK. Based on table above, the researcher product is cheaper than available product in the market. This condition can be happened because we only calculated modal cost while the other price is informed as selling price.

We also compare the specification of each product as below:

Table 21. Specification comparison of available ventilator No Specification Allied 200 BPPT3S-LEN DHARCOV-

23S

Author’s product 1 Ventilation

mode Assist-control Volume-

control

Volume- control

Volume- control 2 I:E Ratio Ti = 1 or 2 s 1:2 1:1 – 1:3 1:1 – 1:4 3 Respiration

Rate

0, 5-30 BPM 10-30 BPM 10-30 BPM 10-30 BPM

4 Tidal Volume 200 – 1200 ml 250 – 450 ml 250 – 650 ml 400 ml 5 PEEP PEEP adapter,

0-20 cmH2O

Variable valve, 5-10 cmH2O

5-10 cmH2O (opsi 5-25

cmH2O)

Not defined yet

6 FiO2 100% 50-90% Not mentioned Not defined yet

7 Alarm function

Yes Yes Yes Yes

8 Power supply 2 x D cell batteries

220VAC, 12VDC, 10A

Not mentioned 220VAC, 24VDC, 10A 9 Battery back-

up duration

2 hours Not mentioned Not mentioned 2 hours

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10 Display Analogue LCD HMI on 7”

touchscreen

LCD 20x4 characters 11 Dimension 88.9 x 177.8 x

236.2 mm

30 x 50 x 50 cm

50 x 40 x 20 cm

40 x 25 x 14.5 cm

12 Weight 1.4 kg Not mentioned 20 kg 10 kg

Product Testing in BPFK

Prototype has been done with the internal performance test then is allowed to continue the process with product testing in BPFK. During this product testing, they will test for the product safety (electrical and mechanical), performance and reliability. Since November 2020, they do the test refers to SNI ISO 80601-2-12:2020. Due to this standard, the reliability test is running the device/prototype continuously for 7x24 hours.

Figure 4.7. Flow process of product testing in BPFK

Unfortunately, the prototype is not running well during reliability test and stop to run when it has 59 minutes remaining. The initial analysis due to this condition are:

- Boost converter become hot due to work continuously for couple hours. As mentioned on its specification that it should be enhanced with heat dissipation

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if output current is more than 8A. Operating temperature of the boost converter is up to 85°C.

Figure 4.8. Boost converter 400W 15A DC-DC (source: www.tokopedia.com)

- Due to high temperature inside the prototype, it makes controller board doesn’t work properly, included with the microcontroller. On the Figure 4.9 is shown that the prototype is on RUN status but actually the motor is not running at that time and the microcontroller doesn’t generate any PWM values to the motor.

We need to analyze deeply regarding to this case.

- Hot temperature is trapped inside the prototype because the enclosure is not designed with good air flow circulation. As a follow up, we need to analyze the enclosure design not only about the material selection but also the air flow circulation and heat dissipation.

Figure 4.9. Status of prototype testing in BPFK