Solid state relay project

Discussion in 'The Projects Forum' started by Clinton Brits, Jul 7, 2016.

  1. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    I spent the last week trying to complete an optocoupler - triac circuit in the hope I could control 220Vac.

    I am now at a point where I'm was confident at an attempt but haven't been able to turn the load. I have gone through various sources and for the life of me I cannot understand why and to be honest I was expecting it to stay on and to not turn off.

    I have uploaded the actual photo of the circuit and the connections. If anyone has succeded and would be so kind as to point out a connection error or pin error I would really appreciate it.

    circuit_800x908.jpg
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,524
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    Can you post a schematic?
    Have you seen the Fairchild app note AN-3006?
    Max.
     
  3. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    I'm using a datasheet schematic for the opto. I'll check the doc you uploaded
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The app note shows a fairly identical circuit.
    Do you mean it does not turn on at all?
    Max.
     
  5. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    It doesn't turn on. That's why I connected the led on the optocoupler - I thought there migh have been a problem. I'm considering doing the circuit again on a breadboard to get it working before pulling out the solder iron.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Zero cross switching types as this are usually easier/simpler to implement than the phase angle switching versions.
    Max.
     
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Not all optocouplers have identical pinouts, so make sure the schematic matches your part.

    ak
     
  8. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    I specifically chose the components for that exact reason.
     
    MaxHeadRoom likes this.
  9. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    Update : We have this circuit working with an optocoupler that does not have zero crossing but seems to not work with ones that do. I'm busy playing around with proteus that shows the same result so hopefully should have it puzzled out soon.
     
  10. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    Could I ask you to check my understanding of the symbol of the triac and the pins of the device?

    I have Live attached to pin one(MT1) and neutral attached to load attached to pin 2(MT2). The resistors are attached to pin1(MT1) and then to the opto and then the gate. Result : Nothing happens.

    If I connect the resistors to Pin2(MT2) and then to the optocoupler that switches the gate we then have it working as usual!?

    I love that it works but having something work and not knowing why is just idiotic.
     
  11. Clinton Brits

    Thread Starter New Member

    Aug 8, 2015
    15
    2
    Problem Solved! If anyone wants to try this the circuit I photographed was almost correct. Live still goes to pin 1. Neutral still goes to pin 2. The resistors that go into the optocoupler must connect the optocoupler and pin 2(Not 1!). The 50nf capacitor should connect the gate and pin 1.

    This is really cool!
     
    MaxHeadRoom likes this.
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