Remote Control of Microcontroller-Based Infant Stimulating System

Journal of Medical Systems, Vol. 24, No. 2, 2000

Remote Control of Microcontroller-Based Infant Stimulating System Mustafa Burunkaya1 and I˙nan Gu¨ler1

In this paper, a remote-controlled and microcontroller-based cradle is designed and constructed. This system is also called Remote Control of Microcontroller-Based Infant Stimulation System or the RECOMBIS System. Cradle is an infant stimulating system that provides relaxation and sleeping for the baby. RECOMBIS system is designed for healthy full-term newborns to provide safe infant care and provide relaxation and sleeping for the baby. A microcontroller-based electronic circuit was designed and implemented for RECOMBIS system. Electromagnets were controlled by 8-bit PIC16F84 microcontroller, which is programmed using MPASM package. The system works by entering preset values from the keyboard, or pulse code modulated radio frequency remote control system. The control of the system and the motion range were tested. The test results showed that the system provided a good performance. KEY WORDS: microcontroller; control; remote control; cradle; infant stimulating system.

INTRODUCTION Crying in infancy is the most frequent complaint from parents to physicians. It is also a symptom of distress and activation of physiologic stress responses from infants.(1) Constant or frequent carrying, rocking, and swaddling of the baby may be the most effective method of controlling crying.(2) But it is not possible for many parents and not reasonable for others. Using a cradle, it is possible to solve this problem. Rocking of the baby was incorporated into a cradle to provide relaxation and sleeping for the baby when the mother was not there. The movement of the cradle represents the mother’s motion from the mother’s movement. This effect is generally soothing to the infant as evidenced by reduced crying or fussiness and promotion of relaxation and sleep.(3) For this reason, the cradle is described as an infant sleeping and relaxation system. In addition to this, the cradle is also a play place for the baby. The baby 1

Electronics & Computer Education Department, Faculty of Technical Education Gazi University, 06500 Teknikokullar, Ankara-Turkiye. 131 0148-5598/00/0400-0131$18.00/0  2000 Plenum Publishing Corporation

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plays with his/her toys safely in the cradle. Today’s cradles are designed with safety and comfort for baby. All parents want to keep their babies in a safe place in their home.(4) The cradle may be the safest place for the infant. One of the parts of the cradle is a fence system. The fence system of the cradle is made of iron rods that go around the cradle. For this reason, if the parents don’t want, the baby can not go out of the cradle. In addition to this, pets such as cats, dogs, etc. can not enter into the cradle. The cradle can also be covered by a large tulle cover. In this way, the baby is protected from insects such as flies and mosquitoes. It is seen that, the cradle is really a safe place to protect the baby against many dangers. As the baby grows older, he/she can spend a lot of time in the cradle; therefore the cradle is very important for the baby. RECOMBIS system is used to provide safe infant care and relaxation and sleeping for the baby. It provides these by movement (rocking) with in the limits of 52 cycles/min periods. It is also a play place for the baby who can play with his/ her toys in a safe environment. RECOMBIS system works by entering preset values from the keyboard. In addition to the keyboard, system functions can also be controlled by a radio frequency remote control system. Because the remote control system is a radio frequency remote control system, transmit and receive direction of the remote control system do not depend on the unique direction. In this way, if the baby cries, RECOMBIS system is quickly and easily operated by somebody using a remote control transmitter. So the baby cries less, relaxes and sleeps more.(5) In this way, the mother does not have to sleep with the baby at night and she does not go about her chores during the day with him/her. In this paper, a new cradle is designed while considering advantages of microcontrolled systems; the new design is compared with other existing systems. The major advantages of the designed cradle are as follows: Among the cradle control systems, one of the most reliable ones is the microcontrolled type. In addition to the reliability of the system, simplicity and smallness are the other advantages as well. The system is programmable, and low-cost. The cradle system operates at two different motions and speed or rocking range and can operate at different speed. Motion speed can be increased or decreased in this range. In other words, the level of motion stimulation of the cradle can be adjusted. Because the RECOMBIS system has the microcontroller based controller unit, only changing the software can change system functions, and there is no need to change the hardware. As there are a few circuits used in the control card of the RECOMBIS system, these are fitted in a single board. In this way, the cost and the noise level during its operation are reduced. Consequently, the desired system functions are obtained effectively.

RECOMBIS SYSTEM RECOMBIS system consists of mainly four units as shown in Fig. 1. One of them is the mechanical system that is not investigated. The others are the electronic controller system, the moving or rocking system, and the remote control system.

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Fig. 1. A block diagram for the RECOMBIS system.

Using the remote control system, preset values can be set to operate the cradle system. In addition to this, preset values can also be set by using a keyboard. There are two electromagnets and four opto-switches in the rocking system. Electromagnets provide the rocking for the cradle. Opto-switches are used to limit the rocking range of the cradle. Opto-switches are also the component of the electronic controller circuit. One of the units of the electronic controller circuit is an oscillator that produces clock signals for the microcontroller. A relay provides isolation between the control system and the power supply. Power supply provides the power for the operation of the RECOMBIS system. The main component of the electronic controller system is a microcontroller that controls all the system functions of the cradle. The circuits of the cradle system are fitted in a single board (or control card). The electronic detail of the control card of the RECOMBIS system is shown in Fig. 2. A software was developed to control the device. The flow chart of the program is shown in Fig. 3. MPASM software is used for the microcontroller programming. Cradle system must be switched-on by a main switch and on/off function must be activated on the control card so the cradle system can operate. Rocking range values and on/off functions can be set using the keyboard on the control card or pulse code modulated radio frequency transmitter/receiver system. These values are stored in memory addresses. Two led diodes on the control card indicate that preset rocking range. Rocking ranges are presented by a unique single key, which corresponds to it. The cradle operates at digitally set values, which were input from the keyboard or by the remote control system. The whole control process is done by the microcontroller itself. Some precautions are taken during the software development for possible system missuses. If the user wants to operate the cradle without

Fig. 2. Control card circuit diagram: (a) Radio Frequency pulse code modulated remote control transmitter, (b) Radio Frequency pulse code modulated remote control receiver, (c) RECOMBIS system control circuit.

Fig. 3. The flow chart of the program.

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giving any rocking value, the system operates the lowest rocking range or the first rocking range. The minimum and maximum rocking range lengths are 2 cm and 5 cm, respectively. At any time, the user can stop the operation of the cradle by a switch placed on the control card. In this system, the desired rocking range values are entered via keyboard as shown in Fig. 2. If the first rocking range is set, first A electromagnet is energized then B electromagnet is energized, respectively, by I/O ports of the microcontroller. The cradle moves in the direction of the energized electromagnet and then moves opposite of this direction. The rocking range of the cradle is limited by A1 and B1 opto-switches for the first rocking range. If the second rocking range is set, first A electromagnet is energized then B electromagnet is energized, respectively, by the I/O ports of the microcontroller. The cradle moves in the direction of the energized electromagnet and then moves opposite of this direction. The rocking range of the cradle is limited by A2 and B2 opto-switches for the second rocking range. The motion speed can be controlled more precisely by changing the program on the card. Motion speed is set by changing the time. The Electronic Blocks of the RECOMBIS System The control card of the RECOMBIS system consists of mainly three electronic circuit blocks as shown in Fig. 2. Two of them are Radio Frequency Remote Control Transmitter and Radio Frequency Remote Control Receiver that are shown in Figs. 2a,b. These are called the RF Remote Control System. Another circuit is the RECOMBIS System Control Circuit that is shown in Fig. 2c. The RF Remote Control Receiver and RECOMBIS System Control Circuit are fitted in a single board. RF Remote Control System General purpose radio frequency pulse code modulated remote control system is developed for the RECOMBIS system. In addition to the keyboard, system functions of the cradle can also be controlled by this RF Remote Control System. Carrier frequency of the remote control system is about 300 MHz. These circuits operate effectively 20 m in diameter distance, and have the capability of 16 channels number. Only four of them are used in this application. Unused channels can be used for the system development or next research. Channel number of the remote control system can be increased by changing carrier frequency of the system. Transmit and receive direction of the remote control system is not depend on the unique direction. In addition to these advantages, as the RF Remote Control System is pulse code modulated, it is very safe for the telecommunication between the transmitter and the receiver system. RECOMBIS System Control Circuit RECOMBIS System Control Circuit controls all the functions of the cradle. A microcontroller is the brain of the control card. All control processes, such as rocking ranges, speed, time and reading of information that comes from optotransistor and keyboard and also energizing the electromagnets are done by this element. PIC16F84 microcontroller has a 36 byte RAM, 1K EEPROM memory,


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13 input and output legs and 1 timer. PIC microcontrollers have the proper hardware, memory and software to control a stand-alone machine or system.(6) Microcontrollers require some simple peripheral circuits when they are used for circuit designs as shown in Fig. 2. For example, the power supply is used to supply required energy for both microcontrollers, and its associated circuits. The oscillator is used to provide a clock signal for the timer circuit of the microcontroller. Crystal 4 MHz was chosen because of the required processing speed.(7) Opto switches are used to limit the rocking range, which the cradle is operating. Four LED diodes indicate that on/ off state and which rocking range is operating. There is a button under every LED in the control card. Functions can be set easily with these buttons and there is an only one main switch that is used to turn-on/off the system. All the controls of the RECOMBIS system are done by these buttons or remote control system.

RESULTS AND DISCUSSION RECOMBIS system is the first evaluation system that we implemented mainly to elicit infant behavioral responses such as relaxation and sleeping. In this paper, only the motion system and its control were investigated. The mechanical system, cradle and others such as mattress pillow, and bolster pads are not investigated. As these parts of the system are very important for infant’s comfort (relaxation and sleeping), they should be investigated. There are two electromagnets in the RECOMBIS system. These electromagnets are used to rock the RECOMBIS system. Some electrical characteristics of the electromagnets were measured by a RLC meter and an Ohmmeter. Measurement results are given in Table I. The meaning of the symbols that are used in Table 1 and Table 2 are as follows: R: DC resistances of the each electromagnet were measured by an ohmmeter in ohm. L: Inductance of the electromagnets, which were measured by a RLC meter in mH. Rp: Parallel resistance of the electromagnets in the equivalent circuit in ohm. ⌽: Phase angle of the electromagnets in degrees. l: The destination, which the RECOMBIS system moves (rocks) between two points in the rocking range.

Table I. Some Electrical Characteristics of the Electromagnets Symbols L D Q Rp Rs Z Lp Ls ⌽ R

Electromagnet 1

Electromagnet 2

424,7 mH 0.707 1.41 5.660 k⍀ 1.887 K⍀ 3.628 K⍀ 636.9 mH 424.7 mH 54.7⬚ 77 ⍀

422.5 mH 0.714 1.40 5.619 K⍀ 1.897 K⍀ 3.256 K⍀ 635.6 mH 422.4 mH 54.6⬚ 77 ⍀

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Burunkaya and Gu¨ler Table II. Some Electrical Measurement of the RECOMBIS System

Veff (V)

Vdc (V)

Idc (A)

VL1dc (V)

IL1dc (A)

P1 (VL1⫻IL1)

VL2dc (V)

IL2dc (A)

P2 (VL2⫻IL2)

Cycles /min

L (cm)

55 60 65 70 73

69,4 75 84,2 87 99

0,786 0,881 0,988 1,022 1,156

77,3 78,2 79,1 87,46 88,2

0,785 0,849 0,922 0,933 1,122

60,6805 66,3918 72,9302 81,6002 98,9604

76,5 78 79,93 87,63 88,7

0,751 0,835 0,909 0,939 1,118

57,4515 65,13 72,6564 82,2846 99,1666

45 52 52 52 52

1,5 1,7 1,8 2,9 5

Z: Impedance of the electromagnets in ohm. The power of the electromagnets was measured. Measurement results are given in Table II. The Relation Between the Destination and the Electromagnetism of the Electromagnets There is a relation between the power supply of the electromagnets and their electromagnetism as shown in Fig. 4. The relation between the destination of the rocking range and the electromagnetism is shown in Fig. 5. If the destination is shorter, the electromagnetism is bigger. In addition to these, there is no relation between the number of the rocking of the cradle and AC power supply voltage. This is shown in Fig. 6. The Performance of Two Levels Rocking Range of the RECOMBIS System The RECOMBIS system is used to elicit infant behavioral responses such as relaxation and sleeping. In this study, only motion system and its control were investigated. There are two rocking ranges in the RECOMBIS system. The RECOMBIS system allows the infant to self-regulate his/her discomfort by movement (rocking) within the limits of 52 cycles/min periods for the each rocking range.

Fig. 4. The relation between the electromagnetism and AC supply voltage for each electromagnet.


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Fig. 5. The relations between the destination of the rocking range and AC power supply voltages.

The cradle moves two different maximum limits for the each rocking range. The destination limits of the each rocking range are shown in Table II. Destination limits of the second rocking range of the cradle are longer than those in the first rocking range. For this reason, the RECOMBIS system is operated in the second rocking range for the first time to provide relaxation and sleeping for the baby. Then, if it is necessary or the baby does not sleep, it can be operated in the second rocking range. The system operation was controlled and the motion range was tested and measured as shown in Table II. The test results showed that the system provided a good performance. Although some professionals have expressed concern that a mechanical device which provides a modulated stimulus environment may decrease mother-infant contact or interaction and could subsequently have a negative impact on the motherinfant attachment relationship, it seems improbable that reducing the incidence of night time crying behavior, in particular, would negatively affect the infant-parent relationship. A transition environment may increase ability of the newborn to self-

Fig. 6. The relation between the number of the rocking of the cradle and AC power supply voltage.

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regulate, cry less, sleep for longer periods, and demonstrate improved behavioral responses to the external environment. We believe, as the other researchers, that these behaviors are advantageous to the infant and they will likely facilitate the development of a positive mother-infant relationship. However, the RECOMBIS system and other analogous systems have a disadvantage. The level of motion stimulation may be somewhat excessive for unstable apnea infants. Therefore necessary precaution must be taken during its use. In addition to this, there is a problem about the electromagnets. As there is power consumption over DC resistance of the electromagnets, heat energy occurs when the electromagnets are energized. For this reason, necessary precautions must be taken. For example, the cradle system should not be operated longer than 30 min. An electronic stimulating system that indicates infant presence and crying in the cradle may be added into the system in the future. In addition to this, 10-min and 20-min timing period rocking functions may be added into the RECOMBIS system. So, in this way, it may be more practical to use.

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