PLC transistor output and relay output difference - Database & Sql Blog Articles

ESD electrostatic protection tube 5V two-way 0201

1. Load voltage, current type Different load types: Transistors can only have DC load, and relays can be used with AC and DC loads.
Current: The transistor current is 0.75A maximum and the relay is 2A maximum.
Voltage: The transistor can be connected to DC 24V (generally the maximum is about 30V DC, the relay can be connected to DC 24V maximum 30V or AC 220V).
2. The load capacity is different. The capacity of the transistor with load is less than the capacity of the relay with load. When using a transistor, sometimes other things are added to drive large loads (such as relays, solid state relays, etc.).
3. The transistor overload capability is less than the relay overload capability. Generally speaking, when there is a large inrush current (such as a bulb, an inductive load, etc.), the transistor has a small overload capability and needs to be derated more.
4. The transistor response speed is faster than the relay relay output type. The principle is that the CPU drives the relay coil to make the contacts pull in, so that the external power supply drives the external load through the closed contact. The open circuit leakage current is zero, and the response time is slow (about 10ms). .
The transistor output type principle is that the CPU turns the transistor on and off by optical coupling to control the external DC load, and the response time is fast (about 0.2ms or less). Transistor outputs are typically used for high speed outputs such as servo/stepping for output with high frequency of operation.
5. Under the rated working condition, the relay has an action life, and the transistor only has an aging time limit.
The relay is a mechanical component so it has an operational life. The transistor is an electronic component. It is only aged and has no limit on the number of uses. There are limits to the number of switching cycles per minute for relays, while transistors do not. The transistor also has a large current, such as 5A or more. It is the output of the transistor. When there is a relay connected to the relay, pay special attention to the polarity of the relay coil (the protection coil or indicator light is connected to the coil), otherwise the transistor will be burned out.