Cattle and horse experiments in the industrial training center
Three voters:
- Purpose
1) Identify the function description of the digital IC.
2) Test digital integrated gate circuits, master output troubleshooting and use precautions.
3) Master logic functions to build a three-person voting device.
2. Experimental resources
HBE hardware basic circuit experiment box, multimeter
74LS00 NAND gate, 74LS10 three 3-input NAND gates, 74LS20 two-input NAND gates
3. Experimental tasks
Design a 3-variable majority voting circuit (when 2 or more of the three input terminals input "1", the output terminal is "1"), and then implement the logic circuit designed by yourself on the experiment board, and verify whether correct.
- Experimental principle
Designed with 74HC00+ 74HC10, each of the three people controls one of the three buttons A, B, and C, and votes on the principle of minority obeying the majority. Pressing down means agreeing, otherwise it means disagreeing. If two or more people agree, the light-emitting diode will light up, otherwise it will not light up.
Experimental circuit:
truth table
74LS00 four-input NAND gate
74LS10 three-input NAND gate
NAND gate voltage transfer characteristic curve
- circuit design
First select the K1, K2, K3 light tubes of the test box as the signal lights for voting. According to the experimental diagram, wire 1 is connected to pin 1 of 74LS00, wire 6 connected in parallel with wire 1 is connected to pin 9 of 74LS00, wire 2 is connected to pin 2 of 74LS00, and wire connected in parallel with wire 2 3 is connected to No. 4 pin of 74LS00, wire 4 is connected to No. 5 pin of 74LS00, and wire 5 connected in parallel with wire 4 is connected to No. 10 pin of 74LS00. Pins 3, 6, and 8 of 74LS00 are connected to pins 1, 2, and 13 of 74LS10 respectively, and pin 12 of 74LS10 is connected to the L10 display tube. At the same time, pin 14 and pin 14 of 74LS00 and 74LS10 are respectively connected to the positive and negative poles of the power supply, and pin 7 and pin 7 of 74LS00 and 74LS10 are grounded at the same time.
Experimental phenomenon and verification:
According to the experimental phenomenon in the figure, when 0 or 1 light is on, it is not passed, when 2 or 3 lights are on, it is passed, and the experiment is successful.
Eight-person answering machine:
- Purpose
1) Know the eight-person answering machine circuit
2) Master the module circuit layout on the universal board
- Experimental resources
HBE hardware basic circuit experiment box, multimeter, oscilloscope, layout software, welding toolbox, universal board, eight-person answering machine main board, 74LS48, unit common cathode digital tube
- Experimental task
1) Know [eight-person answering machine circuit]
Step 1: Clear. The referee first advises everyone to leave their hands. If you keep pressing CLR, you will not be able to answer quickly. Release CLR to start answering.
Step 2: The referee releases the CLR and starts answering. The player who presses first grabs and latches the display (equivalent to only using a 3-digit code and does not use the 74148 priority), and other players who press it later cannot change the result even if they press it multiple times.
In the HBE hardware basic circuit experiment box [drive unit digital tube], record and test the circuit function.
- Master the module circuit layout on the universal board
【*】Download and install the layout software to complete the [universal board layout] of the digital tube circuit of the unit.
- Circuit soldering fabrication and verification
4. Experimental results
- The digital tube of the drive unit displays numbers 0-8
- Universal board module circuit layout
- Circuit Soldering and Fabrication
Experiment summary:
- Through this experiment, I learned the working principle, design and production of the three-person voting device and the eight-person answering device. Recognized and understood the functions and pin assignments of several chips. study
- I learned how to basically use the experiment box for circuit connection to realize some circuit functions, learned the connection methods of various wires, and how to insert the chip into the experiment board.
3. Learn to use software to layout the module circuit on the universal board
4. Learn to solder and make circuit boards
Humanities:
There are still many deficiencies in this experiment. For example, I didn’t preview and understand the relevant content in advance, which led to the failure to keep up with the teacher’s pace in class, and the experiment was always a step behind. Another example is that the experiment operation is improper, the wire connection position is wrong, and the switch has not been turned on for a long time during the experiment, and the reason cannot be found.