What do you need to know about reed relays?
Reed relays contain a reed switch, a coil for creating a magnetic field, an optional diode for handling back EMF from the coil, a package and a method of connecting the reed switch and the coil to outside of the package. The reed switch is a simple device and relatively low cost to manufacture.
When do the contacts close on a reed switch?
The contacts in the normally open reed switch close in the presence of a magnetic field. The contacts stay closed as long as the magnetic field remains. The contacts open once the magnetic field is removed.
Which is better a reed switch or an armature switch?
Reed switches have been manufactured since the 1930s. Compared with armature-based relays, reed relays can switch much faster, as the moving parts are small and lightweight, although switch bounce is still present. Also, they require less operating power and have lower contact capacitance.
How is a reed switch turned into a normally closed switch?
It can be turned into a normally closed switch by applying a permanent magnet with a field strong enough to close the reed contacts. This biasing magnet must be greater than the pull-in field or operate field that closes the contacts in the normally open condition. The polarity of the magnet does not matter.
What does DC protection with relays do for speakers?
Speaker DC protection with relays. Introduction. An important feature of an audio amplifier is to provide a system to protect your speakers in case the amplifier breaks down and puts DC on the speaker terminals. No speaker will take kindly to the presence of 50V on it’s voice coil, so that has to be prevented.
How to use Elec circuit for speaker protection?
Experiments DC voltage protection, connect DC voltage at the IN of any speakers, the LED will extinguish along with the relay will stop immediately. All full-size images of this post are in this Ebook: Elec Circuit vol. 2 below.
How to build diyaudio speaker delay and DC protector board?
1. Setup a suitable power transformer. You can use a 9VAC to 12VAC if you use 6V relay coils or 18VAC to 24VAC is you use 12V relay coils. 2. Connect the probes of your DMM to AMP_IN_1 and SPKR_1. Set to check for resistance.