Bear in mind this is a general guide only and you should check the data sheet for exact information. As a general guide, optocouplers are most efficient at about 10mA. The value of the CTR changes depending on the input current and the ambient temperature. The Fairchild 4N26 has a CTR of about 20%. Most optocouplers have a CTR of between 10% and 50%. It is similar to the DC current amplification ratio of a transistor and is expressed as a percentage. ![]() The CTR is the ratio of the phototransistor collector current compared to the LED emiiter forward current. The main things you need to know when choosing an optocoupler are: It will not work if you get them the wrong way-a-round. The shutter wire from the shutter release cable goes to pin 5 and ground from the shutter release goes to pin 4. You need to add a suitable resistor to the input, see below. ![]() Note that the +5 volts (VCC) from an Arduino digital pin goes to pin 1 and Arduino ground goes to pin 2. Pins 1 and 2 go to the Arduino, pins 5 and 4 go to the cable release. No current on pins 1 and 2 means current does not pass through pins 5 and 4. Basically, if you put a current through pins 1 and 2 and light the LED the photo detector transistor detects the light from the LED and allows a current to flow through pins 5 and 4. This means they can be used to allow one circuit to switch a separate circuit without having any electrical contact between the two. They work by using an LED emitter paired with a photo detector transistor. I already had a Fairchild 4N26 so this is the one I used. Due to the relatively low voltages there are many suitable optocouplers to pick from. My intention was to create a automatic shutter trigger for my Canon camera, so the circuit was a 5V Arduino and a Canon 40D which has about 3.2V on the shutter release connections. MODEL I_SW1 ISWITCH (Roff=1e6 Ron=1 IT=4.9m IH=0.There are many types of optocoupler and you chose one based on the requirements of your circuit. MODEL MOST1 NMOS (LEVEL=3 KP=25U VTO=2 RD=45) MQ1 VO 9 GND GND MOST1 W=9.7M L=2U NMOS OUTPUT In order to be 100% sure that the LTspice version of the 6N137 was as relevant as the original Pspice model, I reproduced a circuit present in the data sheet and computed the switch time announced in the spec. The new subckt file can be found in appendix in the zip simulation file and also in the "code section", together with usable symbol. Using Spice/PSpice (Vishay optocoupler) models in LTSpice - Electrical Engineering Stack Exchange The simulation in LTspice crashed because the Pspice model contained features not supported by LTspice, Fortunately, I found a fix for that at the following address. I was surprised that the importation of the Pspice model ( pspicevo.pdf () ) was not as straightforward as it used to be. ![]() Also I found a very relevant spice model for the digital 6N137 optocoupler commercialized by Vishay. I wanted to illustrate one more simulation of temperature control with NTC thermistor, using an optocoupler as a modern switch, and to show once more how we can combine electronic simulation and thermal engineering with the wonderful simulation software offered by LTspice. NTC thermistors, optocouplers and temperature control.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |