Relay Substitution

About: I spent my career in computer networks. Now retired I am interested in topics that work my neurons. I am passionate about home automation and site administration that I host at home. I acquired skills in the...

The conventional circuit for actuating a relay transistor (NPN or MOSFET), may be replaced by a Reed relay.


Reed Relay

Teacher Notes

Teachers! Did you use this instructable in your classroom?
Add a Teacher Note to share how you incorporated it into your lesson.

Step 1: Description of the Concept

Advantages :

  • Reduced number of components
  • Space saving
  • Simplifying installation
  • Connects directly to TTL output
  • Low cost


Limited Switching Power ~ 10W (there are models to 20W).

Technical data:
A reed switch is a magnetic switch, placed in a glass bulb, of which two contacts are made of iron-nickel alloy. In the presence of a magnetic field, contacts magnetize and are attracted to each other.

The maximum input current (TTL output) varies depending on the components between 10 and 16mA. The resistance of the relay coil must be greater than 500 ohms in order to limit to 10mA for a 5V supply.

The maximum cut-off intensity varies between 0.5A and 1A according to the relay model.

The diode is essential. It protects the input device when the current flowing in the relay coil is cut, causing a high voltage to the relay coil.

Relay corresponding to the above specification Reed Celduc D31A3110 (or equivalent PRME 15005, Edr0201 a0500, SIP1A05).

The cost is less than € 5.

Used worldwide microcontrollers (see application project on my site )

Be the First to Share


    • Made with Math Contest

      Made with Math Contest
    • Multi-Discipline Contest

      Multi-Discipline Contest
    • Robotics Contest

      Robotics Contest

    2 Discussions


    20 days ago

    I don't know whether you are suggesting using the left side switch or the right side? there is no link to the actual devices either way?

    I am interested in this and would like to make it a latching relay for say 2 minutes . Could you suggest a way to do that please?

    1 reply