Standard DB9 connectors allows easy connection of any standard DB9 serial cable. The power supply is galvanic isolated from the rest of the isolator which ensures noise or surges from the power supply enters the isolator this gives an additional level of isolation.īaud rates of 300 to 115200bps and indication LED lights for TX, RX and Power makes this isolator easy to use and compatible with most serial devices. This isolator must be powered by an external 9 to 18 VDC power supply. High-speed 6N137 opto-couplers from Fairchild Semiconductor is what ensures protection and high performance in this isolator. Static electricity and other high voltage surges is protected against for up to 15KV. Optical isolation for up to 2500 Vrms and continuous 500VDC ensures effective protection against voltage spikes and surges and ground loops. What we have here is a high-speed industrial grade RS232 optical isolator which provides isolation for all 8 communication wires. max load voltage currently only 100V (less for some versions), whereas some opto types can be > 1000Vįor more detailed information on general SSR functions, the following article is useful.low isolation voltage (only about 200V, compared to >1KV for most others).no wear-out mechanism (LED types degrade over time).smaller size (requires less space than opto interface).higher operating temperature capability of +105 ☌ (most others are +85 ☌).lower input current (0.2mA max) required to turn on, vs.Check the datasheets and other manufacturer documents to find the highlighted features and specs unique to each product.įor example, here is a summary of the Panasonic AQY2C product mentioned earlier: SummaryĮach design has its pros and cons, or to be more precise, applications where it is best suited. These are “hybrid” in the sense that they include isolation, but are not truly solid state given the presence of moving contacts. Similar designs use the basic principle of a reed relay within the overall SSR topology. In general, these designs are only partially solid state, but they may provide isolation (depending on design), and some of the problems encountered with mechanical relays are averted.Įxamples can be found in the OMRON G9H series. There may also be references to “hybrid” SSRs. Be sure to read the “Important Notice for TI Reference Designs” at the end of the article, as there are rules regarding the use of this material. Note the circuit diagram and partially populated bill of materials. Texas Instruments has a reference design for this type. Source of images: Transformer IsolationĪ third isolation technique within SSRs is through transformer inductance. The datasheet shows the internal structure and a comparison to other SSR types within the series: This works by generating an oscillating signal which is capacitively coupled across the isolation barrier, and which is then used to charge the gates of the output MOSFETs. Within the Panasonic AQY2 series, some part numbers with an AQY2C prefix use this configuration. Part number 306-1308-ND is another example of optical coupling (Coto Technology number C347S).Īn alternative is capacitor coupled isolation. Image source: [click here $file/LCB716.pdf Part number CLA311CT-ND is one example (IXYS number LCB716STR). The output side may vary, but all optically isolated SSRs will look similar in this regard. Note the photodiode and coupling symbols that are common in all of those. Most random picks will produce an optically isolated device. Here is the main category for solid state relays. The Digi-key site currently (as of this posting) does not include a filter for the isolation type, so it’s important to recognize the optical feature in a drawing. Although they are not common, a few non-optical types are commercially available.Ĭontinue with an optical isolation review or jump to:įirst, let’s quickly review the optical isolation structure. However, any isolation mechanism could theoretically be incorporated into an SSR. With optically isolated solid state relays (SSR) so common, it’s easy to assume that all of these products will use that coupling architecture.
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