Find a self-locking relay switch circuit (using D flip-flop)

dinghao1

You need to use a button, a D flip-flop, a relay and a peripheral circuit to design a switch with a self-locking function. Press the button once and the relay will close. Press the button again and the relay will open. Please give me the circuit diagram.

Arvinˇ

5 Chip Coins, walked away with disdain~

dinghao1

Arvinˇ posted on 2018-9-11 08:35 5 core coins, walked away with disdain~

Don't go, do you have a circuit?

maychang

Take 74HC74 as an example: connect the Q non-output terminal to the data input terminal D, input the key signal from the CP terminal, and each rising edge of CP will change the Q terminal level (the original high will become low, and the original low will become high). The J and K terminals must be connected to a high level. This is actually a T flip-flop.

maychang

In the actual circuit, the key signal must be shaped before it can be sent to the CP terminal of 74HC74. Because the key always jitters, the circuit may flip many times when the key is pressed once.

dinghao1

maychang posted on 2018-9-11 09:05 In the actual circuit, the key signal must be shaped before it can be sent to the CP end of 74HC74. Because the key always jitters, the circuit may happen very...

Thank you, is there any circuit reference?

dinghao1

maychang posted on 2018-9-11 09:05 In the actual circuit, the key signal must be shaped before it can be sent to the CP end of 74HC74. Because the key always jitters, the circuit may happen very...

Can the output of Q be directly connected to the relay?

RF-刘海石

In fact, it is the standing wave protection circuit of the RF power amplifier. If you check it, the reverse voltage is greater than the forward voltage. It is equivalent to your key, giving a high-level pulse, and then passing through a D flip-flop (an operational amplifier will do), feedback plus 2 diodes, outputting a high level, that is, locked. At this time, the relay is energized, but unlocking requires another switch, or reset. The relay is disconnected.

dinghao1

RF-刘海石发表于2018-9-11 09:34 It is actually the standing wave protection circuit of the RF power amplifier. If you check it, the reverse voltage is greater than the forward voltage. It is equivalent to your button, giving a high level pulse, ...

Thank you, I need the one that only uses one button

maychang

dinghao1 posted on 2018-9-11 09:15 Thank you, is there a circuit reference?

Refer to this circuit. Screenshot from Kang Huaguang's "Electronic Technology Fundamentals Digital Part 5th Edition" Chapter 5, page 231.

maychang

dinghao1 posted on 2018-9-11 09:27 Can the output of Q be directly connected to a relay?

The output capacity of a digital circuit is not that large and cannot directly drive a relay. At least another transistor must be used.

huo_hu

Oh, why don't you just change the button to one with a lock?

dinghao1

maychang posted on 2018-9-11 09:41 Refer to this circuit. Screenshot from Kang Huaguang's "Electronic Technology Fundamentals Digital Part 5th Edition" Chapter 5, page 231.

OK, thank you

maychang

huo_hu posted on 2018-9-11 09:44 Oh, why don't you just change a button with a lock?

The question of the original poster is a homework assigned by the teacher. In actual work, when using buttons to control relays, relays with additional contacts are used, with two buttons, one normally open and one normally closed, one responsible for the relay to attract and the other responsible for the relay to release.

huo_hu

maychang posted on 2018-9-11 10:31 The question of the original poster is a homework assigned by the teacher. In actual work, when using buttons to control relays, relays with nearby contacts are used, two buttons, ...

Yes, in order to allow other protection circuits to be cut off

Arvinˇ

For a button without self-locking function, it is possible to achieve self-locking with only a D flip-flop (a transistor self-locking circuit will do), but it is unlikely to also have an unlocking function at the same time.

maychang

[quote]Arvinˇ posted on 2018-9-11 17:41 For a button without self-locking function, it is possible to achieve self-locking with only a D flip-flop (using a triode self-locking circuit), but it is not possible to achieve the unlocking function at the same time. No problem at all. Just look at the truth table of the T flip-flop and you will know.

topwon

The S pin is equipped with a capacitor, so the final state of power-on initialization is S pin = L, R pin = H, so the initial state of Q should be H. If you want to change the initial state of Q to L, you should move the C3 capacitor to the R pin.