Zero-cross SSR for AC load switching
The Panasonic AQH2213 is a solid-state signal relay from the AQ-H series, switching AC loads up to 900 mA across a 0-600 V range. The SPST-NO (1 Form A) output uses zero-cross turn-on, meaning the relay fires at the AC voltage zero crossing — this minimises inrush current into capacitive or cold-filament loads and reduces conducted EMI at switch-on. The input side triggers at 1.21 VDC, compatible with standard logic-level or microcontroller GPIO outputs without an external driver transistor. The 8-DIP through-hole package (0.300-inch row spacing, 7 leads) suits point-to-point wiring on a control PCB or socketed installation in a panel-mount relay base.
Load voltage range and output isolation
Rated for 0 V to 600 V AC across the output, the AQH2213 covers common line voltages from 24 VAC control circuits up to 480 VAC motor contactor coils and heater loads. The 900 mA continuous current at 600 V gives a switching capacity of 540 VA — sufficient for driving small contactors, solenoid valves, or indicator lamp banks in a panel. The zero-cross output type means the relay only turns on when the load voltage is near zero; turn-off occurs at the next current zero crossing. This behaviour is inherent to the triac output stage and eliminates the arcing and contact wear of an electromechanical relay in AC circuits. The trade-off is a minimum load current requirement — below the holding current of the internal triac the output may not latch off cleanly, so verify the load draws at least a few milliamps.
Package and board integration
Housed in an 8-DIP with 7 leads (pin 7 is omitted for clearance), the AQH2213 fits standard 0.300-inch wide DIP sockets or solders directly into a through-hole PCB. The PC pin termination style provides a reliable solder joint for industrial environments where vibration is present. The AQ-H series uses a moulded plastic body with a standard DIP footprint. No heatsinking is required at 900 mA in still air at 25 °C ambient, but derate the load current if the relay shares a densely populated board or sees elevated enclosure temperatures.