SSR01 - Dual Solid State Relay

Submitted by GG on Sun, 12/01/2013 - 22:54
Project Status

ssr01 pth version Many MCU applications use electro-mechanical relays to control AC loads. While this is an excellent solution for occasionally turning on/off a load it is not suited for frequent switching or PWM applications. SSR01 is an opto-coupled solid state relay that can control two AC loads up to 16A each.


High Voltage Parts of this circuit are not isolated from earth ground and contain potentially lethal voltages. Avoid touching any part of the circuit when powered on.
Use a safety isolation transformer during experimentation and troubleshooting.

ssr01 smd version


  • support either PTH or SMD triacs
  • optional support for anti-parallel SCR configuration (instead of triac)
  • support either zero-cross (MOC306x) or non zero-cross (MOC305x) switching
  • optional triac snubber
  • optional I2C RTC clock

BOM notes

For zero-cross switching use MOC306x type opto-couplers, for random phase switching use MOC305x opto-couplers.

Configuration T3/T1 T4/T2 T5/T6 D3/D4/D5/D6 R5/R7/R9/R11 R6/R10
Triac SMD no stuff no stuff BTA216 no stuff 360 0
Triac PTH no stuff BTA216 no stuff no stuff 360 0
SCR PTH BT151 BT151 no stuff S1J 330 360
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The MCU is connected using GPIOs. There is one pin for each of the two channels.