/challenges-projects/design-challenges/experimenting-with-thermal-switches/b/challenge-blog/posts/auto-cutoff-circuit-for-room-heaters---blog-1Auto-Cutoff Circuit for Room Heaters - BLOG 1 This is the first blog in the Experimenting with ...en-USTelligent Community 12https://community.element14.com/challenges-projects/design-challenges/experimenting-with-thermal-switches/b/challenge-blog/posts/auto-cutoff-circuit-for-room-heaters---blog-1Sun, 30 Jan 2022 13:58:50 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a4769556-5d24-4fc4-a582-8721886f2a77Gough Lui1<p>A heater overheat protection sounds like a perfect application for a thermal switch.</p> <p>As the switch output is a binary switching of a contact, perhaps you could drive the relay directly through the thermal switch itself and avoid the need for an op-amp as long as the relay coil current is within the rating of the switch (0.1/0.3/0.5/0.55A depending on the model). Don&#39;t forget to have a back-EMF protection diode on the relay coils.</p> <p>It may be nice to have the circuit powered from the mains as well, for convenience.</p> <p>Another thing to think about is the safety of the circuit itself - perhaps it would be best to design it in such a way that it is &quot;fail-safe&quot; - i.e. the heater is turned off if the battery runs out or power is lost.</p> <p>- Gough</p><img src="https://community.element14.com/aggbug?PostID=22810&AppID=359&AppType=Weblog&ContentType=0" width="1" height="1">