Interesting human reaction speed test circuit

The human body reaction speed tester introduced here is mainly composed of 4 digital circuit chips and 10 LEDs, etc. It can measure the human body's reaction time to the signal and divide the reaction time into 8 segments. The higher the segment number, the faster the reaction speed. Frequent reaction test training can gradually improve the human body's reaction speed.

The reaction tester consists of power-on delay, test signal light, clock pulse, subtraction counting, start display, stop control, etc. The following figure is a control principle block diagram.

Control principle block diagram.

This circuit is mainly composed of 3 types of 4 CMOS digital integrated circuits. The circuit schematic is shown in the figure below. IC1 is a four-2-input NOR gate circuit 4001, IC3 and IC4 are inverters 4069, and each chip contains 6 independent inverters with large current driving capabilities, which can directly drive light-emitting diodes. The pin numbers of each integrated circuit are marked in the schematic diagram. For more detailed chip characteristics, please refer to relevant information.

IC2 uses a dual 4-bit static shift register 4015. The pin function is shown in the right figure (omitted). It contains two independent 4-bit serial-in and parallel-out shift registers. In this circuit, two groups are cascaded. Each group of registers has a clock terminal CLK, a reset terminal RST, and a serial data input terminal D. The output terminal of each register unit is led out, so it can be used for both serial output and parallel output. The data added to the D terminal shifts to the right under the action of the rising edge of the clock. When "1" is added to the reset terminal RST, all the registers are zero. In this circuit, two groups of registers are cascaded. The truth table of 4015 is shown in the table below.

Truth table of 4015

IC2 uses a dual 4-bit static shift register 4015

2. Circuit working process

After the power switch K1 is closed, the power indicator LED10 lights up, and then after a delay of several seconds, the test signal light LED1 lights up, and the subtraction counter circuit begins to decrease under the action of the clock pulse, and the test display light-emitting tubes composed of LED2 to LED9 go out one by one. During this process, when the person being tested presses the stop button K2, the clock pulse stops oscillating, the subtraction counter is in a holding state, and the number of LED2 to LED9 that go out will be recorded as the reaction time of the person being tested.

3. Working Principle of the Circuit

IC4E, IC4F, R16, R17, C4 and other components form a multivibrator. As a clock pulse, its oscillation period is about 212×R17×C4. According to the parameters in Figure 3, the period is about 44 rns. IC2 (4015) forms an 8-bit right shift register, and IC1B, R1, C1 and other components form a power-on delay circuit. When the power switch K1 is just closed, the output of IC1B is "1". Under the action of the clock pulse, the 8-bit register unit of IC2 quickly becomes "1". After a few seconds, the output of IC1B becomes "0". After the two-stage reversal of IC3A and IC3B, the test signal light LED1 is driven to light up. At the same time, the 8-bit register unit of IC2 will change to "0" from left to right in turn under the action of the clock pulse. When the person being tested presses the stop button K2, the RS trigger composed of IC1C and IC1D is set to "O", so that IC4E and IC4F stop oscillating, and IC2 is in a hold state. The result is displayed by driving the light-emitting diode through IC3C~IC4D. The function of IC1A here is that pressing the stop button K2 is effective only when the test signal light LED1 is on. Pressing K2 in advance is invalid.

How the Circuit Works

4. Production process

The full set of components of this tester is shown in the figure below (omitted). The component list is shown in the table below. It is recommended to check the component parameters and quantity one by one against the component list before assembly. After confirming that they are correct, you can start assembly. In principle, the order of soldering components should follow the principle of first short and then high, first small and then large.

Complete set of components for the tester
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The following figure is a diagram of the component position installation. When looking at the integrated circuit chip from the front, the side with the semicircular notch faces left. Insert the chip on the printed board according to the markings on the printed board. The recommended welding sequence is:

(1) Solder the resistors, jumper wires (J1 to J6), and diode 1N4148.

(2) Welding ceramic capacitors, electrolytic capacitors, switches and buttons.

(3) Solder and install 10 LEDs.

(4) Solder four CMOS integrated circuit chips.

(5) After everything is completed, carefully check whether each soldering point is firm and whether there is any short circuit or open circuit. If necessary, you can turn the board towards the light to check the soldering condition.

After confirming that everything is correct, solder the battery leads. Be careful to distinguish the positive and negative leads. Then install 4 AA batteries and power on for testing.

Component location installation diagram

5. Welding precautions

When soldering CMOS digital integrated circuits, be careful to ground the soldering iron reliably, or unplug the power plug and solder with residual heat to prevent induction static electricity from breaking through the CMOS chip. There are 6 jumper wires on the printed board, represented by J1 to J6, and can be soldered with the extra component pins cut off. The longer pole of the LED pin is the positive pole, and the one with a small straight line on the outer circle is the negative pole. It can be installed according to the character identification on the printed board. The end of the 1N4148 diode tube with a black ring is the negative pole. C1 and C5 are electrolytic capacitors, and the shorter end of the pin is the negative pole. There is usually a "-" mark on the outer skin. The leads of the battery box are correctly connected according to the "+" and "-" polarities marked on the printed board, and never connect them in reverse. After all components are soldered, it is also necessary to carefully check whether the components have been installed correctly, whether the solder joints are firm, and whether there are short circuits between the pads and the traces to ensure that the assembly is correct.

6. Power-on test

After a thorough inspection, you can connect the battery for testing.

Close the power switch K1, the light-emitting diode LED10 lights up, indicating that the power is on, and then LED2~LED9 are quickly lit. After a delay of a few seconds, LED1 lights up, indicating that the test has started, and LED2~LED9 quickly go out in sequence. At this time, press the stop button K2, and LED2~LED9 will stop going out immediately and retain the state. Since the period of the multivibrator is about 44ms, the reaction speed of the person being tested can be calculated by calculating the number of LED2~LED9 that go out. For example, after pressing the stop button, LED2 to LED5, a total of 4 LEDs, go out, then the reaction speed of the person being tested is 44ms×4=176ms, that is, 0.176s. If the circuit does not work properly, please carefully check whether the assembly is correct. According to the working process, compare with the schematic diagram, and check the fault point step by step.

In fact, by changing the parameters of R17 or C4, the frequency of the multivibrator can be adjusted, that is, the test speed can be changed, which has increased or decreased the test difficulty. Changing the parameters of R1 and C1 can change the delay time of the test after power-on, making it difficult for the testee to master the test rules, and improving the accuracy and interest of the test. When the second test is required, turn off the power switch K1 for a few seconds, then turn it on again to perform a new test.