Understanding Reed Switches & Reed Relays
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- เผยแพร่เมื่อ 26 ก.พ. 2024
- This video describes what reed switches and reed relays actually are. It details how they work and how they are used as well as giving some circuit design hints and tips.
The reed switch is the basic element and this consists of two ferromagnetic reeds or contacts held within a glass envelope. The reeds overlap so that when they close they make contact.
When a magnetic field is applied, the reeds become magnetically orientated to the field, making the two ends of the reeds opposite poles.
When the external field becomes sufficiently strong, the attractional force will draw to each other, closing the contact and making the circuit - the basic reed switch. Essentially it is a magnetic switch.
These reed switches are used for many applications including sensors, i.e. magnetic reed switch sensors, etc.
Reed switches also form the main element of a reed relay and they are used in electronics as fast acting mechanical switches.
The bar magnet we saw earlier can be replaced by a coil. When a current passes through the coil a magnetic field is created and this acts to switch the reed relay over.
Reed relays come in a variety of sizes and formats. They can be dual in line, single in line for PCBs of they can be much bigger for larger current applications. There are several manufacturers of reed relays so there is a good choice.
Reed relays are used in circuits for many reasons: they are fast acting, they are reliable, they have a low ON resistance and high OFF resistance and they also provide isolation between the actuator and switched sides of the circuit.
To find out more about reed switches and reed relays check the following link: www.electronics-notes.com/art...
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thank you for the video, its very helpful
I’m really glad you found the video useful. Thanks for your comment.
Does the orientation of the reeds and or the the magnetic field come into play?
Not that I am aware of. They seem to demagnetise well after the field is removed , so it does not appear to be an issue.
Can you please discuss the various methods of recovering the BEMF generated when a relay coil is de-energised.
Recovery values of 80-90% of the input power in a pulsed relay driver circuit are possible, given the correct circuit/coil parameters.
Cheers.
This is not something I have done, but I am sure there is someone out there who has done it. When I’ve used them I have not been in a situation where I needed to recover the back EMF.
@@ElectronicsNotesI have working examples in my Lab if your interested in further discussion/schematics.
@@ricksampson6780 that would be interesting. Thanks.
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