Is the diode soldered facing to the left or to the right? (The same image is found on page 3 of the datasheet linked below.)

Enter image description here

Some information:

  • The relay is part of a "soft-start" circuit; AC passes through an NTC thermistor for a few moments and then when the relay is triggered, VAC will be passing through the relay switches.
  • The relay "IN" pin is connected to mains AC (115/230 VAC).
  • The coil (as stated on the relay body) is rated at 12 VDC.
  • Relay datasheet. Looking at the datasheet and the markings on the relay, I believe I have the "1FormA" with pin 6 on page 3.
  • 1
    \$\begingroup\$ There's no polarity for the single coil non-latching relays. How's the relay driven? Via a transistor? \$\endgroup\$ Commented Oct 31, 2022 at 7:43
  • \$\begingroup\$ @RohatKılıç yes. via transistor. \$\endgroup\$
    – mrjayviper
    Commented Oct 31, 2022 at 8:04
  • 1
    \$\begingroup\$ Then see kruemi's answer below. The cathode goes to positive rail, and anode goes to collector (if BJT-driven) or drain (MOSFET-driven) of the switching device - assuming you are driving a low-side switch. \$\endgroup\$ Commented Oct 31, 2022 at 8:06

2 Answers 2


The flyback diode is part of your layout and not of the relay, so looking at a usual, unpolarized relay won't help you find out how to install a flyback diode.


simulate this circuit – Schematic created using CircuitLab

The diode is installed in a way that it does not conduct current when the relay is energized.

When SW1 is opened, the inductivity of the coil has stored energy that keeps the current flowing. Now, the current can flow through the diode and thus slowly dissipate.


The diode direction is dependant on the polarity of the voltage applied across the coil.

enter image description here


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