I would like to use a 12V relay in my LTspice circuit, however there is no relay in the component list.

How can I do?

Relay model: SRD-12VDC-SL-C

  • \$\begingroup\$ I edited your post adding a link to the datasheet. Would you mind to confirm that the relay you are using is that shown in the datasheet. Otherwise you may want to provide a link to the correct datasheet. \$\endgroup\$ Aug 15, 2015 at 18:33
  • \$\begingroup\$ I found this very easy and useful: analog.com/en/technical-articles/… \$\endgroup\$
    – AmirSadri
    Jul 23, 2020 at 20:10

2 Answers 2


As @KevinWhite said, you can use a voltage controlled switch. Here is an example of a very rough model for a relay:

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And this is the result of the simulation:

enter image description here

The model is very rough because:

  • The excitation coil is modeled only by a resistor, neglecting the inductive component (this may be OK).
  • The switch triggers when a voltage is applied to the terminals of the coil, whereas physically the relay triggers when the current in the coil is sufficiently high to move the contacts.

Both points above can be neglected unless you need to simulate the exact behavior of the relay under transient conditions (switching delays, oscillations, contact bounces, etc.).

An inductor in series with the coil resistance can be useful to simulate the inductive kick the relay produces when switched off.


You can use a voltage controlled switch to simulate the contacts (Just called SW in LTSpice).

Set the operating voltage to match pull-in voltage of your relay.

You can use a resistor (and an inductor if desired) to simulate the relay coil.

Here are a couple of useful links: Relay Model Voltage controlled switch example


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