Two basic functions of intermediate relays in practical applications:
1. The expansion of the intermediate relay contacts is generally used in the main circuit:
For example, the intermediate relay is used in the main circuit, and is connected in parallel with the AC contactor to expand the contacts of the AC contactor to make up for the shortcomings of insufficient contact usage.
2. Electrical isolation is generally used in control circuits:
This is the principle we usually use: small current to control large current, small voltage to control large voltage, and isolation of large current and large voltage in the main circuit.
We look at the intermediate relay in the picture, 13---14 power supply wiring, 1--5--9, 9----5 normally open point, 1--9 normally closed point.
The same 4---8---12=4--12 normally closed point. 8----12 Normally open point.
The physical application of the intermediate relay: how to use a micro relay to control the load, in the picture we use a relay to control a light, 13---14 is connected to the power supply, the neutral line enters the light directly, the live line enters the relay normally open point 9, and it exits through the normally open point It is 5, connected to the light, when the relay is energized, the normally open contact is closed, and the light is energized to light up.
Relay normally open---normally closed use=13---14 connect to the relay power supply, the neutral wire enters two lights respectively, the live wire enters the relay common terminal 9, and then 5 goes out to enter the light, terminal 1 goes out to enter the light, and the micro-relay is initialized The light on terminal No. 1 will light up, because 1---9 are normally closed points, and the light on terminal No. 5 will light up when the relay is energized. Because the relay is energized and the normally open contact is closed, the light will light up.
The photoelectric switch controls the miniature relay: First, we use the relay to control the alarm, and the alarm sounds when the power is turned on, so we use the photoelectric switch to control the relay. Since we control the relay, we need to control the coil of the relay, as shown in the figure. When the photoelectric switch is touched, the relay will be energized and the alarm will sound.
The working principle of the photoelectric switch 220V plus the intermediate relay alarm: First of all, the electrical components used in the picture are 220V, so the power supply is connected to the neutral wire, and the live wire enters the normally open contact of the relay respectively, and the contact enters the power supply of the alarm. The photoelectric switch is connected, the neutral line enters the photoelectric switch, the relay coil 13 is normally open through the photoelectric switch, and the live line enters the coil 14 of the relay. When we touch the photoelectric switch, the normally open point of the photoelectric switch is closed, and the relay coil is energized. , The normally open contact is closed, and the alarm will sound. When we leave the photoelectric switch, the normally open point will be disconnected, the relay will lose power, and the alarm will stop sounding when it loses power. This is how the photoelectric switch controls the relay. And how the relay is used in the actual circuit to transmit the signal.