With Scientific and Technological progress and Industrial Development, through the Computer to realize the Automatic Control has been widely used in many Industries. Depending on the Control Object, Device interface requires a Computer with external Devices should have High Switching Speed, anti-interference Ability, Power drive is Small, output Power, INPUT and output on the isolation between the Electrical characteristics. Solid State Relay (SSR) is an Ideal one interface Device.
SSR is an isolated Electronic Controller, shown in Figure 1 the Shape. SSR used between the INPUT and output coupling, and THEREFORE Electrically completely isolated. Compared with the Mechanical relay, SSR has a Wide Range of applied Voltage, Power drive is Small, non -contact, no spark, no noise, vibration, moisture resistance, corrosion resistance, anti-interference, switching speed, long life and other characteristics, widely used in machinery, chemicals, food, cigarettes, electronics, stage lighting, etc. with the Computer I / O interface or Requirements without Noise Control areas. The SSR does not have the Power of Ordinary Instruction, to Understand the on-off State to be measured by Instruments, not Too convenient. This Paper describes a Power-Improved with SSR Directions , the on-off status indication by LEDs, the long-term use, works well.
Circuit and technology parameters
SSR from the input circuit, isolation circuit and output circuit consists of three parts, the principle block diagram shown in Figure 2.
INPUT Stage with Constant Current Circuits, SO IT that can Adapt to a Wide Range of INPUT Voltage. The INPUT characteristics shown in Figure 2. Isolation level using Optical Couplers, the INPUT and output in the Electrical Circuits Circuit is completely separated. By the Optical Detector output Stage Driver Circuit composed of two-Way and the absorption of Thyristor Circuit Transient suppression. SSR Electrical schematic Diagram shown in Figure 3.
D1, D2 from the symbol-bit role, so BGl, BG2 composite pipe the output current does not increase with the input voltage increases linearly to achieve constant current input e D3 LED to indicate working status, optocouplers electrically isolated from the role of IC. D4 for the two full-Bridge-Way S. Thyristor Trigger Signal R5 and C Components Absorb Network.
SSR characteristics of the technical Parameters including INPUT and output characteristics. Input features such as listed in Table 1. Output characteristics as listed in Table 2.
Parameter name parameter value
Min Typ Max
3V 42V input voltage
Input current 20mA
ON voltage 2.8V
Turn-off voltage 1.5V
Dielectric strength 1.5kV
Parameter name parameter value
Min Typ Max
Input Voltage 25V 380V
Input current sub block
2.0V output voltage drop
Output leakage current 10mA
Ambient temperature-20C +80 ° C
Production and Application
Production of Printing plates used in SSR shown in Figure 5. Production, according to the underlying Parameters used in Figure 4 Components, and Welding by conventional methods. But to note the following: (1) Rated output Current Greater than 2A, the Thyristor and the shell at the End of the Metal Heat SINK should be coated with between Thermal Grease, a Good Contact. (2) to determine the correct Thyristor T1, T2 and the Gate G, the specific methods are as follows: with a Multimeter Rxl00 block If one measured the resistance of the foot and the other two legs are infinite, the pin T2 pole. Determine the T2 extreme, the use of multimeter Rxl block, the black pen then T2, the red pen then assume that T1 pole, and to assume that T1 pole and assume G very transient short answer it, if T1 and 12 to maintain the turn, and then the red pen then T2 pole, black pen then assume that the T1 table with G very very short answer it, if the turn can be maintained, that assumption was correct. Conversely, the other pole is assumed to be T1 pole, repeat the above operation; if not turn on, that thyristor is damaged. (3) finished products in addition to input and output parameters of the tests, but also for the dielectric strength test, that is, between the input and output voltage plus 1750V and maintain more than 30s.
When using the SSR, the input part of the TTL devices can control the control transistor can also be used, or even directly using 3 ~ 42V DC power supply; its output can be single part of the control, shown in Figure 6, Figure 7, the multiple control shown in Figure 8, SPDT control (equivalent to a pair of normally open normally closed contact) Figure 9.