The circuit is an automatic polarity switch when you press a button.
Where might this be needed? Yes everywhere. Well, for example, in some toys. The car reached the wall, pressed a button - the car went back :) In fact, there are a lot of applications. Meanwhile, the device is extremely simple. Consists of only two microcircuits and several hanging elements.
Start over. That is, from a button.
As you, I hope, know, all switches, buttons, relays and other elements of mechanical switching have a very unpleasant property: “bouncing” of contacts. It is expressed in the fact that when a pair of contacts is closed, the current does not immediately begin to flow calmly through them. At first it “rattles” for some time - it makes damped oscillations. When the contacts are opened, the same problem occurs.
Often no one notices or takes into account the chatter, since for most circuits it does not pose a serious problem. But for our scheme this is a real problem. Because when the button is pressed once, the circuit will “think” that the button was pressed several times, which, of course, will lead to glitches. This means we need to fight him.
To combat bounce, our device has a clever circuit consisting of two inverters of the K561LN2 microcircuit, a capacitor and two resistors. We will not delve into the details of his work. Let me just say that this circuit is a Schmidt trigger with a time delay on and off. In short, after this circuit we get beautiful rectangular pulses without any chatter.
These beautiful pulses are sent to the clock input of the trigger DD2 (561TM2). On each edge (change from 0 to 1), the trigger slams the state at input D. The signal to input D is supplied from the inverted output of the same trigger.
Then everything is very tricky. Let’s assume that the inverse output is 1. At the next front, it slams into the trigger, therefore, “1” appears at the direct output of the trigger, and “0” at the inverse output. This means that at the next front, a zero will slam into the trigger! In this case, “0” will appear at the direct output, “1” will appear at the inverse output again, and the process will begin again.
Thus, each edge will change the state of the flip-flop to the opposite.
In principle, we already have a polarity change at the trigger outputs each time the button is pressed. And if the load is low-power, you can stop there and hang it directly on the outputs of the microcircuit. However, it is better not to overload the microcircuit with current, but to install the most ordinary transistor amplifiers at its outputs. More precisely - drivers.
A driver is a buffer amplifier that amplifies the digital signal by current.
In principle, this is what we need. We will install one driver for each trigger output. Each driver consists of two transistors of different conductivity. When a positive voltage is supplied to the driver input, the NPN transistor is open, when negative, the PNP is open. I installed transistors KT502 and KT503 (PNP and NPN, respectively) in our circuit. These transistors can easily withstand currents up to 100 mA. What? Do you need more? OK! You can install more powerful transistors.
The circuit is an automatic polarity switch when you press a button.
Where might this be needed? Yes everywhere. Well, for example, in some toys. The car reached the wall, pressed a button - the car went back :) In fact, there are a lot of applications. Meanwhile, the device is extremely simple. Consists of only two microcircuits and several hanging elements.
Start over. That is, from a button.
As you, I hope, know, all switches, buttons, relays and other elements of mechanical switching have a very unpleasant property: “bouncing” of contacts. It is expressed in the fact that when a pair of contacts is closed, the current does not immediately begin to flow calmly through them. At first it “rattles” for some time - it makes damped oscillations. When the contacts are opened, the same problem occurs.
Often no one notices or takes into account the chatter, since for most circuits it does not pose a serious problem. But for our scheme this is a real problem. Because when the button is pressed once, the circuit will “think” that the button was pressed several times, which, of course, will lead to glitches. This means we need to fight him.
To combat bounce, our device has a clever circuit consisting of two inverters of the K561LN2 microcircuit, a capacitor and two resistors. We will not delve into the details of his work. Let me just say that this circuit is a Schmidt trigger with a time delay on and off. In short, after this circuit we get beautiful rectangular pulses without any chatter.
These beautiful pulses are sent to the clock input of the trigger DD2 (561TM2). On each edge (change from 0 to 1), the trigger slams the state at input D. The signal to input D is supplied from the inverted output of the same trigger.
Then everything is very tricky. Let’s assume that the inverse output is 1. At the next front, it slams into the trigger, therefore, “1” appears at the direct output of the trigger, and “0” at the inverse output. This means that at the next front, a zero will slam into the trigger! In this case, “0” will appear at the direct output, “1” will appear at the inverse output again, and the process will begin again.
Thus, each edge will change the state of the flip-flop to the opposite.
In principle, we already have a polarity change at the trigger outputs each time the button is pressed. And if the load is low-power, you can stop there and hang it directly on the outputs of the microcircuit. However, it is better not to overload the microcircuit with current, but to install the most ordinary transistor amplifiers at its outputs. More precisely - drivers.
A driver is a buffer amplifier that amplifies the digital signal by current.
In principle, this is what we need. We will install one driver for each trigger output. Each driver consists of two transistors of different conductivity. When a positive voltage is supplied to the driver input, the NPN transistor is open, when negative, the PNP is open. I installed transistors KT502 and KT503 (PNP and NPN, respectively) in our circuit. These transistors can easily withstand currents up to 100 mA. What? Do you need more? OK! You can install more powerful transistors.
High-power electronic MOSFET switches are a staple in consumer and specialty electronics and can be useful for controlling large DC loads without using high-current switches that can burn out and wear out contacts over time. As is known, MOSFET field-effect transistors are capable of operating with very high voltages and currents. Which is highly in demand for connecting loads in different power circuits.
Electronic switch circuit
This circuit allows easy switching of low voltage pulses (5V) to drive large DC loads. The power of the MOSFET transistor indicated in the circuit is suitable to withstand voltages and currents up to 100 V, 75 A (for NTP6411). This electronic switch can be used instead of relays in your vehicle's modules.
A regular switch or pulse input can be used to activate the transistor. You can select the input method by installing a jumper on the appropriate side. The pulse input will probably be most useful. The circuit was designed for use with 24V, but it can be adapted to work with other voltages (tests were fine at 12V). The switch must also work with other N-channel MOSFETs. A protection diode D1 is included to prevent voltage surges from inductive loads. LEDs provide a visual indication of the transistor status. Screw terminals allow the device to be connected to different modules.
After assembly, the switch was tested for 24 hours together with the solenoid valve (24 V / 0.5 A) and the transistor was cool to the touch even without a radiator. In general, this circuit can be recommended for the widest range of applications - both in LED lighting and in auto electronics, to replace conventional electromagnetic relays.
