SOLID STATE RELAYS SERIAL CONVERTERS & SOLID STATE RELAYS Start using solid state relays today The fundamental functions within the majority of process control systems involve repeatedly performing a switching action. Solid state relays (SSR) offer the user many outstanding benefits for this type of switching. Selection and application is easy and here are a few simple guidelines and suggestions to help you make the most of this technology. Amplicon Serial Comms Why choose Amplicon for serial communications? Amplicon’s broad range of serial communication products serves industrial markets as well as IT applications throughout the world. As a manufacturer we have attained a high level of expertise resulting in outstanding product quality and first rate technical knowledge. What is a ‘Solid State Relay’? A ‘Solid State Relay’ is a switching device which uses transistor technology instead of mechanical contacts to do the switching function. This switching is performed by a Triac or SCR (Silicon Control Rectifier) dependant on the load type. Both these switching devices are members of the Thyristor family, and input to output isolation is achieved by the use of an optocoupler. Typical SSR Internal Construction Advantages of solid-state v electromechanical relays 90-280 Vac. The control voltage is considered similar to a relay coil voltage. Advantages: Long life and high reliability, more than 109 operations, reduced maintenance costs • No contact arcing, low Electromagnet Interference (EMI) and high surge capability • High resistance to shock and vibration • Fast switching and low coupling capacitance • Logic compatibility and no electromechanical noise Disadvantages: • Higher cost than equivalent electromechanical relay • Higher heat dissipation requires heat sink Heating Applications Selecting the correct SSR for your application Two output types exist within AC switching SSRs. The first is commonly referred to as ‘Zero Voltage’ or ‘Zero Crossing’ turn-on. This type only starts to conduct once the AC line voltage has passed through the zero volt point. The second type is referred to as ‘random’ or ‘instantaneous’ turn on. This type begins to conduct as soon as the control voltage is applied regardless of the AC line voltage. A choice of control voltages are available; low voltage DC control – typically 3-32Vdc, or high voltage AC control – typically 14 AUTOMATION APRIL 2008 Heating applications have repeated frequent load cycling as the elements are turned on and off to maintain the required temperature. Heating elements are predominately resistive, so surge currents at switch-on are low. This makes Zero Voltage turn on SSRs ideal for heating applications. Choosing the suitable solid-state relay is easy to do if you consider the following: • Full Load current of the elements • Line voltage being switched • Available heat sink - oversize where possible, or select a device with integral heat sink • Ambient temperature - in heating applications elevated temperatures are common and you may need to de-rate the SSR Therefore, to maximize the life expectancy of the SSR, the selected device will have a continuous rating of at least 2x the full-load current, Zero Voltage turn-on and a voltage rating higher than the supply voltage. AC Motor and Coil Control Applications Because of the inductive nature of AC Typical ‘Hockey Puck’ type SSR motors, and solenoid coils, high surge currents occur at switch-on. This makes random or instantaneous turn on SSRs the most suitable type. When selecting a suitable SSR for these applications you must consider the following: • Full Load current of the motor or coil • Line voltage being switched • Starting duration and frequency - repeated cycles will increase thermal stress on the SSR requiring extra heat sinking or overrating • Ambient temperature and available heat sinking Due to the high current during start-up the SSR must be over rated, compared to the full load motor or coil current. For motors, external over current protection is always advisable to protect both the motor and the solid state relay. This could take the form of a motor protection circuit breaker or thermal overload. Voltage selection is important as back EMF generated during motor wind-down or turn-off of a large coil can be x1.5 – x2.5 line voltage. To ensure the maximum operational life the selected SSR, it should have a current rating of at least 3x the full load current, random turnon, and an over-voltage rating of more than twice the line voltage. n Latest technologies from the leading automation brands RS232 to RS422/485 converters Serial to Ethernet converters Amplicon have manufactured RS232 to RS485 converters for over 20 years. Serial to Ethernet converters offer a cost-effective solution for the integration of legacy serial equipment (RS232, RS422 or RS485 devices) into modern Ethernet networks. • Convert RS232 to RS485 and vice-versa • • • RS232 links up to 1.2km if used in pairs Optical isolation available for data integrity Automatic turnaround for connecting to 2-wire RS485 networks • • • • Transmit serial data across a LAN, WAN or even the internet Use existing networks instead of installing new cable Centralised control of remote devices Easy to configure with 5 year warranty as standard 221-402 Model 232i-9 IN-LINE 1 PORT RS232 ISOLATOR £69.00 221-395 485H-F9 RS232 TO RS422/485 CONVERTER £55.00 221-503 485F9i RS232 TO RS422/485. OPTICAL ISOLATION £75.00 221-367 MA485F9 RS232 TO RS422/485. AUTOMATIC TURNAROUND £65.00 221-519 SE5001-S2 1 PORT RS232 TO ETHERNET CONVERTER £110.00 221-373 USB-232U 1 PORT UNIVERSAL USB TO RS232 ADAPTER £89.00 221-351 SE5001-S5 1 PORT RS422/485 TO ETHERNET CONVERTER £125.00 221-389 USB-485Ui 1 PORT USB TO RS422/485 ADAPTER £119.00 221-200 SW5001 1 PORT RS232/422/485 TO WIRELESS LAN £199.00 Amplicon IT and instrumentation for industry THREE PHASE SSR NEW GN SERIES SMART MODULE NEW GN SERIES SSR WITH HEATSINK A new retro-fittable module which can be mounted on top of a Crouzet GN series or any ‘hockey puck’ solid state relay and provides visual and electrical feedback that an error or failure has occurred. A puck style SSR with pre-fitted finned heatsink and DIN rail mount fitting. Heaksink allows SSR to be used up to its full rating within ambient temperatures up to 40ºC. • INPUT and ERROR LED indicaton • Sense line voltage - 24-660Vac • 4-32Vdc transistor alarm output • Mounts on any standard puck type SSR • 4-32Vdc control input • Zero Volt switching • EMC compliant • LED input status indication The D53TP series provide three phase switching in a compact puck style body using SCR outputs for maximum reliability, with a variety of load types such as motors, heating elements and transformers. • LED status indication • Line voltage – 48-530Vac • Screw terminals • Matching heatsink available – nominally 45mm x 60mm 509-1225 Smart module £24.27 rswww.com/automation 08457 201201 499-0301 7A 24-280Vac SSR £32.96 499-0317 9A 24-280Vac SSR £35.02 499-0323 13A 24-280Vac SSR £37.08 499-0373 15A 24-280Vac SSR £39.18 499-0418 25A 24-280Vac SSR £42.27 499-0424 30A 24-280Vac SSR £43.30 184-5983 25A 3-32Vdc control £62.85 184-5999 50A 3-32Vdc control £70.11 218-1915 25A 90-280Vac control £71.14 218-1921 50A 90-280Vac control £82.99 613-8094 MS3 DIN rail mount heatsink £26.73 AUTOMATION APRIL 2008 15