The idea of a collapsing magnetic field creating a voltage spike is used to great effect in automotive ignition systems. The coil in a car has two windings, not unlike a transformer, but it is switched on all the time when the engine is running. The primary coil gets a 12v source from the engine and creates the magnetic field, then when it is time for the spark plug to go, it is switched off. The collapsing magnetic field induces a very high voltage (often 15-20 kV) in the secondary winding, generating the energy needed for the spark.
Well-explained. I enjoyed that. Thank you. Here's a follow-up question: Since it appears a diode would be need with most or all relay applications, why don't they just include one already installed INSIDE the relay package?
Because that's more expensive and consumers think cheaper = better. But many relays do include a diode. Look at the schematic on the outside of the relay or on the box.
Thanks for explaining how this Works! I just used this today/learned it existed. Built a small pelican case with a mini pc in it. It has a sla battery and a buck converter, as well as "shore power" plug. It only draws 800 ma on the 12V side but the current spike energizing the buck converter fried the main switch. I put a relay in, and when I turned switch off with unit plugged in it disrupted USB devices connected. Put 10a schottky diode on relay and it worked like a champ! No more interference!
If you want to speed up the turn-off time of a relay, you might want to put a zener diode or tvs diode in reverse series with the flyback diode. The voltage depends on the circuit, but the nominal voltage of the relay is a good rule of thumb. The significantly higher voltage drop is able to absorb more power, leading to a faster collapsing magnetic field. You'll definitely like the solid clack that the relay will give when turning off and will hopefully reach higher clock speeds. The benefit in my own projects is mainly that the contacts are less likely to weld due to the stronger return force. But I'm also very pleased with the sound of those well-behaving relays..
That’s ok, but in some sequential circuits made of relays, this is not desirable because that might cause logic glitches or even malfunction. You normally want to have a consistent propagation delay for both transitions 0->1 and 1->0. Having one much faster than the other is definitely a no-no for many designs
@@RelayComputer Interesting! I imagine the delays are not symmetrical to begin with, wouldn't carefully selected diodes and/or resistors make it perform better?
@@peterwilbrink718 I’m not so sure, but I believe once you have a “normal” diode placed in, the release delay mainly depends on the particular relay coil characteristics and the relay “must release” voltage. In my experience, at least with miniature relays, the on/off delay times become very similar after connecting a diode. However, as you point out, the release time is much faster in the absence of a diode, or with a zener in the mix. That’s what /can/ cause trouble in some sequential circuits that rely on such propagation delays to properly work
0:46 it's probably good enough for the purposes of this video, but constant current can create a constant magnetic field. It doesn't have to be changing. But in the other direction: magnetism inducing electricity, it does need to be changing.
GREAT VIDEO!!! How would you protect the driver of an inductive load if it is dual polarity? for example, if the inductor used + AND - signals as in a reversible motor? THANKS MUCH!! and THUMBS UP!
You need to make an informational video on how to properly diode protect your automobile so the average consumer can fight back as shoddy mechanics treating them as cash cows...The comments youll get will be overwhelming when you educate people in a manner that hits them with a hard reality and aids them with a simple solution that saves them mucho deniero..
Is a flyback diode just a rectifier diode but called flyback because of the use case or function it is performing in the circuit or is it a specific type like zener diodes ?
Rectifying diodes(edit: rectifier) are used in ACDC conversation to clamp/block the negative side of the ac wave. Flyback diode is named as such because the sudden voltage spike released by the collapsing mag field flies back into the circuit. So the diode preventing that is named flyback.
