Collection Schematic

A well-known shortcoming of virtually all electronic components is their sensitivity to temperature changes.
Circuit functioning of this SSR circuit is as follows:

lt is true that triacs are not A too bad in this respect, but they do not like low temperatures: they just stop working! This is caused by the fact that triacs require a higher gate current at low temperature. Triacs are often triggered by opto-couplers which are not capable of supplying these higher currents. The circuit described, in contrast to normal .triac triggers, contains an amplifier which ensures sufficient gate current under all temperature conditions; The amplifier is formed by transistor  T1, which raises the signal from the opto-coupler to more than adequate level. The use of capacitor C2 as a dropping reactance ensures that the dissipation in the drive circuit is virtually nil; it also prevents the circuit presenting a dc load to the mains supply. The switch on current surge is limited to a safe value by resistor R3. As the drive circuit is supplied directly from the mains, the mains voltage must, of course, be reduced to an acceptable level. This voltage is therefore rectified by D1  and smoothed by C1. Zener diode D2 stabilizes the supply to the circuit to 15 V. As soon as transistor T1 conducts, capacitor C1 discharges via T1 and the triac gate, provides a gate current of about 40 mA. The discharge time, and consequently the trigger pulse, is not greater than 1 millisecond. RC network R4/C3 protects the triac against high voltage peaks.
Siemens application.  

The complete SSR or solid state relay circuit is shown below.