Design of light controller for spectrum light stimulation myopia therapeutic device

The spectrum light stimulation myopia treatment device stimulates the eyes and acupuncture points around the eyes according to the light spectrum to achieve the purpose of treating myopia.

1 Technical requirements

According to relevant information, the light spectrum uses red, green and blue lights to stimulate the eyes and acupuncture points around the eyes in different time periods. The general requirements are: red light uses weak (bright 1 s), medium (bright 1 s), strong (bright 1 s), stop for 3 s, and cycles for 3 minutes; red (bright 1 s, off 1 s), red (bright 1 s, off 1 s), blue (bright 1 s, off 1 s) cycle for 1.5 minutes; red (bright 0.3 s), green (bright 0.3 s), blue (bright 0.3 s) cycle for 1.5 min.

2 Controller ASM flow chart

According to the above technical requirements, the controller ASM flow chart can be drawn as shown in Figure 1. The system is in the TO (0000) state, receives the MF command, s1 = 1, the control signal CLR = 1, the clock signal is cleared, starts timing, and enters T1.

Cycle 1: TI (0001) state, the red light is weak; when time t=1 s, state signal S2=1, control signal CLR1=1, 1 s is cleared, enter T2 (0010) state, the red light is medium; when time t=1 s, enter T3 (0011) state, the red light is strong; when time t=1 s, enter T4 (0100) state, the red light is off; when time t=3 s, state signal S3=1, control signal CLR2=1, 3 s is cleared; at this time, if time t<3 min, enter T1 (0001) state cycle; if t≥3 min, state signal S4-1, enter T5 state, control signal CLR=1, clock signal is cleared.

Cycle 2: T5 (0101) state, the red light is bright; when time t=1 S, state signal S2-1, control signal CLR1=1, 1 S is cleared, enter T6 (0110) state, the red light is off; when time t=1 S, enter T7 (0111) state, the red light is bright; when time t=1 S, enter T8 (1000) state, the red light is off; when time t=l S, enter T9 (1001) state, the blue light is bright; when time t=1 S, enter T10 (1010) state, the blue light is off for 1 S; at this time, if time t<1.5 min, enter T5 state cycle; if t≥1.5 min, state signal S5=1, enter T11 state, control signal CLR=1, clock signal is cleared.

Cycle 3: T11 (1011) state, red light on, when time t = 0.3 s, state signal S6 = 1, control signal CLR3 = 1, 0.3 s cleared, enter T12 (1100) state, green light on; when time t = 0.3 s, enter T13 (1101) state, blue light on 0.3 s; at this time, if time t < 1.5 min, enter T11 state cycle; if t ≥ 1.5 min, state signal s5 = 1, enter TO state.

The controller design can use the ASM method, draw the state transition table according to the ASM diagram, write the drive equation and output equation, and then use the trigger, data selector and decoder to design. The MDS method can also be used, because there are more states and more input variables, so the MDS method is simpler.

3 Controller MDS state diagram

Draw the MDS state diagram based on the ASM diagram, as shown in Figure 2.

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4 Hardware Implementation

4.1 Component Selection

According to the MDS diagram, a four-bit binary counter 74161 is selected as the basic element. The logic diagram of 74161 is shown in Figure 3, and the function table is shown in Figure 4.

74161 has three operations: counting, holding and preset. In order to make the combination part of the circuit as simple as possible, the counting and holding functions are given priority. According to the MDS diagram and the 74161 function table, the 74161 operation table can be drawn as shown in Figure 5.

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4.2 Find the activation function of the function control terminal and the setting terminal

The function control terminals of 74161 are: Cr, LD, P, T; the setting terminals are: D, C, B, A. In order to obtain the excitation function of each channel, the Karnaugh map of each excitation function is drawn as shown in Figure 6.

Cr is the clear terminal. Since there is no clear operation, Cr=1 in each cell of the Karnaugh map. T and P are the control terminals for counting and holding functions. When P=1 and T=1, counting occurs. When one of P and T is zero, holding occurs. Therefore, T=1 in each cell of the Karnaugh map. P fills in the corresponding conditions in each cell of the Karnaugh map. For example, when P is in the TO state, it counts when S1=1. Therefore, S1 is filled in the TO cell, and the corresponding conditions are filled in the other cells. LD is the control terminal for counting and setting functions. When LD is zero, the number is set, and when it is 1, the number is counted. The number is set only in the T4, T10, and T13 states, and the other states are all counting. In order to simplify the circuit, LD is used to represent it in the Karnaugh map, so 0 is filled in the other tables, and the corresponding conditions are filled in the T4, T10, and T13 cells.

Set the number: At T4, when S3=1, S4=0, transfer to T1, set the number to (0001), so fill in 0, O, O, 1 in D, C, B, A respectively; at T10, when s2=1, S5=0, transfer to T5, set the number to (0101); at T13, when S6=1, S5=1, transfer to TO(0000), when S6=1, S5=0, transfer to T11, (1011), so fill in D, B, A respectively, and fill in C with S5. According to the Karnaugh map, each activation function can be written:

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In order to simplify the circuit, the circuits for clearing CLR at S4 = 3 min and S5 = 1.5 min and clearing CLR1 at S2 = 1 s are drawn in the clock circuit.

5 Controller logic diagram

According to the MDS diagram, excitation function and output function, the controller logic diagram can be drawn as shown in Figure 7; the controller simulation waveform diagram is shown in Figure 8.