Making solid state relay with BT139 a bit confused with

• Making solid state relay with BT139 a bit confused with
  Posted by Chriss on 18 Sep, 2022 22:47
• Hi!
  I have several BT139 and MOC 3021 around and I come across my mind I could make solid state relays for AC loads like AC motors and lamps.
  
  I know, restive and inductive loads are different, I would like to make all them to handle inductive loads, so I need also the snuber circuit if I'm not wrong.
  
  My major problem is to setup the right value on the circuit.
  I checked around the net and found tons of schematic promising to do what is written, but I'm not really trusty to them.
  
  Can somebody pls share a working schematic how to make my relays?
  
  Here is a schematic which looks ok for me, I would substitute the BT136 with BT139, probably not a problem.
  https://www.twovolt.com/2016/11/29/solid-state-relay-using-moc3021-bt136-traic-circuit-pcb-layout/
  
  What is this meaning in the datasheet of the triac:
  Igt trigger current VD = 12 V; IT = 0.1 A; T2+ G+ ?
  What is T2+ G+ standing for?
  
  Any help I would really appreciate.
  
  Thank you.
• #1 Reply
  Posted by nigelwright7557 on 18 Sep, 2022 22:52
• Quote from: Chriss on 18 Sep, 2022 22:47

  Hi!
  I have several BT139 and MOC 3021 around and I come across my mind I could make solid state relays for AC loads like AC motors and lamps.
  
  I know, restive and inductive loads are different, I would like to make all them to handle inductive loads, so I need also the snuber circuit if I'm not wrong.
  
  My major problem is to setup the right value on the circuit.
  I checked around the net and found tons of schematic promising to do what is written, but I'm not really trusty to them.
  
  Can somebody pls share a working schematic how to make my relays?
  
  Here is a schematic which looks ok for me, I would substitute the BT136 with BT139, probably not a problem.
  https://www.twovolt.com/2016/11/29/solid-state-relay-using-moc3021-bt136-traic-circuit-pcb-layout/
  
  What is this meaning in the datasheet of the triac:
  Igt trigger current VD = 12 V; IT = 0.1 A; T2+ G+ ?
  What is T2+ G+ standing for?
  
  Any help I would really appreciate.
  
  Thank you.
  

  
  MT1, MT2 and G are the pins of a triac.
  
  Turn on triac by applying volts across G to MT2.
  
  
• #2 Reply
  Posted by Chriss on 18 Sep, 2022 23:03
• Thanks for fast response.
  
  If I understand you correctly, In the schematic I put on the link, the turn on voltage is achieved through the T1 and G ?
  Would this schematic work in practice?
  
  I'm new to triac's and not really practiced with them, but I'm familiar with AC voltage and safety of mains...
  
  I found this nice doc, maybe somebody who is new to triac can also learn from it, like me.
  https://www.st.com/resource/en/application_note/dm00451014-controlling-a-triac-with-a-phototriac-stmicroelectronics.pdf
  
  Thanks.
• #3 Reply
  Posted by Terry Bites on 20 Sep, 2022 09:23
• I'd read this app note from ST AN437 on snubbers for inductive loads. Choose your C  and with care. CY caps and R that can safely dissipate the transient energy.
  
  Triacs are satan's spawn. I hate 'em.
  DIY dimmer trauma in childhood.
  
  
  
• #4 Reply
  Posted by nigelwright7557 on 25 Sep, 2022 22:52
• Quote from: Chriss on 18 Sep, 2022 23:03

  Thanks for fast response.
  
  If I understand you correctly, In the schematic I put on the link, the turn on voltage is achieved through the T1 and G ?
  Would this schematic work in practice?
  
  I'm new to triac's and not really practiced with them, but I'm familiar with AC voltage and safety of mains...
  
  I found this nice doc, maybe somebody who is new to triac can also learn from it, like me.
  https://www.st.com/resource/en/application_note/dm00451014-controlling-a-triac-with-a-phototriac-stmicroelectronics.pdf
  
  Thanks.
  

  
  The circuit is part of a working circuit.
  You need 5 volts between "TRIAC" signal and ground to turn it on.