Current flow direction demonstrator (III)

The current flow direction demonstrator introduced in this example uses a light-emitting diode to demonstrate the flow direction of the DC current in the wire. When the battery polarity is changed, the flow direction of the current in the wire also changes. Using this device in physics teaching can allow students to intuitively see the flow direction of the DC current.

How the Circuit Works

The current flow direction demonstrator circuit is composed of counter/distributor integrated circuits ICl, IC2, NOT gate integrated circuit IC3, color-changing light-emitting diodes VLl-VL9, diodes VDl-VD6, resistors Rl-R5 and capacitors Cl-C3, as shown in Figure 2-3.

Figure 2-3 Current flow direction demonstrator circuit (III)

The clock oscillator circuit composed of IC3, resistors R1, R2, and capacitor Cl provides counting pulses for ICl and IC2. R3, C2 and R5, C3 respectively form the reset circuit of IC1 and IC2. After the positive electrode of battery GB (3 1.5V dry batteries) is connected to the A terminal and the negative electrode is connected to the B terminal, the power switch S is turned on, the diodes VD1, VD3 and VD5 are turned on, VD2, VD4 and VD6 are turned off, IC1 and IC3 work, IC2 does not work, and the Yl-Y9 terminals of ICl independently output high level in turn, so that the green light-emitting diodes in VL9, VL8...VL1 emit light in sequence (from right to left). If the working pole of GB is connected to the B terminal, the negative pole is connected to the A terminal and then S is connected, VD2, VD4 and VD6 are turned on, VD1, VD3 and VD5 are turned off, IC2 and 1C3 work, ICl stops working, and the Y1-Y9 terminals of IC2 independently output high level in turn, making the red LEDs in VL1, VL2...VL9 light up in turn (from left to right). Adjusting the resistance value of R1 can change the operating frequency of the clock oscillator, thereby changing the speed at which the LEDs light up in turn.

Component selection
Rl-R5 use 1/4W carbon film resistors or metal film resistors.
Cl-C3 use monolithic capacitors.
VDl-VD6 use IN4148 or 2AK3 switching diodes.
VLl-VL9 use 2EF302 three-terminal color-changing light-emitting diodes.
IC1 and lC2 use CD4017 decimal counter/distributor integrated circuits; IC3 uses CD4069 six-not gate integrated circuits.