Your explanation of the use the diode is the best of have seen out on the internet. Thank you for posting!!

Almost. What you need is a snubber. A snubber is a diode in series with a resistor. So, why do you need the resistor. In many electronic circuits, devices are protected from inductive kick back by a diode. The coil in a contactor is not puny like 100 turns of #35 wire on a ferrite coil, it is probably as big as the coil in many magnetos. So, in effect, the diode is shorting out a spark plug when it fires. The diode has a junction that will breakdown because of very high currents in the microsecond range. So, the diode case won't show excessive heat before failure. When the diode junction breaks down, it becomes a resistor and current flows in both directions, shorting the power supply and you have a classic smoke test. A resistor in series with the diode is chosen to limit the current through the diode while also limiting the voltage spike in the surrounding circuit.In most cases, reducing a thousand volts to say 50 volts wins the day. Since the resistor has a higher resistance than the conducting diode it is in series with, most of the energy is dissipated as heat in the resistor instead of the diode. Since resistors are designed to get hot, they can withstand energy dumps that the diode's junction cannot. A diode alone always works for coils connected to delicate printed circuit board leads. That is a low power situation, contactors in aircraft are not comparable. One last thought, make sure you use a non-inductive resistor. Wire wound resistors have measurable inductance.

You would think this would be a standard feature on every automotive contactor. Thanks for the suggestion that we add one to our contactor.

Thank you. I think this simple diode is the reason my friends lift keeps burning up motor controllers. I will pass this info along.

Great explanation - just what I was looking for

4:48 Department of sweeping generalizations 😅 Reminds me of ministry of silly walks

I was involved in building "specialist" vehicles for over 20 years We used contactors sometimes referred to as Klixons to conect dual charge or auxilliary batteries and as generator starters Beware! do not buy a cheap contactor, our buyer, being a cheapskate started ordering chinese components because of price After numerous failures we cut open a few units, the core inside the coil was a simple bolt! This contacted the heads of the two bolts that the wiring was attached to In a couple of instances the bolt heads fused together causing the starter to engage all the time burning out the starter or destroying the ring gear, if in the battery master situation it might mean not being able to switch off systems Buy the best, you will not be dissapointed, also it could save an engine or a life!

great explanation. so, just need to work out, what size diode to use in what system...?

never thought of this , interesting video.

It just kills me to see relays mounted in the vertical fashion in aircraft. One hard landing and a bounce and you can engage the starter, sheer a few teeth or worse. Relays should be mounted in the horizontal fashion. Especially in aircraft. Just my 2 cents.

Love this,should always put a diode across the coil windings to stop back electromotive force

Thank you for sharing.

thank you so much!

every electric coil device usually needs to be protected from back EMF. Relays, soleniods, etc.

Hi my name is Michael and I've built me a Porsche 914 with a 427 Stroker Motor, and I've burnt 2 key switches, so a friend of mine that owns another Porsche Shop told me to put a starter relay like the Ford type, naturally I wanted the best so I went on Amazon and bought a MySpare relay 4 post they gave me to diodes one bigger and one smaller, I couldn't get it to work then I was reading the reviews, and a old farmer said that ya have to ground one of the small posts,so I've done more homework wich led me to your KZfaq, and I'm aware of better Quality Relay, and I am all about better and nothing burning up ,I run Holley Snider Fuelinjected and Msd Timing and Control, that has to go Straight to the Battery, I'm thinking perfect spot for the Diodes, also what type of Lamar or Skytech should I use Before it goes to the Stater Solinoid on the starter ,and the for post do I ground one of the small posts and still run a Diode across both small Terminals ? Aircraft stuff is the Quality I want to be at Overkill every thing no Fires no frying all my Electronics I have a lot of money in it just like Aircraft, can you help me please

Brilliant!

When you talk about the direction of electric flow do you mean “ Conventional “ current flow ( actually proton flow direction ) or actual electron flow ?

Would you also use one on the motor +. -. Wouldn't it also create a inductive load when disengaged maybe causing internal damage.

How would you snub the transient from a mechanical latching contactor?

how do you use a Diode on a 3 post older style Relay "Solenoid"

Use a 24 or 40 Volt MOV instead of a Diode! (Metal Oxide Varistor) It is not polarity sensitive, and keeps the operating characteristics of the relay (contactor) intact! What that simply means, is if a diode is used, it holds the magnetic field intact for upwards of 250 millisecond, allowing the field to collapse slower, thus reducing the voltage spike! The MOV does not slow the response time of the relay like the diode does. FYI, your common variety surge and lightning suppressor uses two 250 Volt MOV's to protect your electronics at home. Diode use for surge suppression is NOT the recommended way to address this problem of voltage spikes from relays. Use the device designed for that purpose, use a 24 or 40 Volt MOV!

thanks for the video:)

Is grounding the circuit through the switch shown here a uncommon way of wiring the circuit? Most times I see running power to the switch---to the solenoid and THEN to ground. There is no information given as to the # of the diode (specifications) to use either. For the uninformed, like me, what size of diode should be used on a 12 or 24 volt starter solenoid??

And, my two cents. I see that your explanation used "Conventional Current Flow" theory - From Positive to Negative. In all reality, the negatively charged particles, the "current" will flow from ground (the air frame, effectively) through the coil, to the Positive terminal of the battery. No big deal, in that the diode is "reversed biased" across the coil, in its installation, then forwarded biased (i.e. the short ckt) when the mag field collapses. Good info though. Thanks. N-6395T

4:29 Does this dissipate through heat?

Where to buy a master starter ?

I need to know the duration of a split moment in either nanoseconds or Fermi Times, your choice.

Operative word when requiring a diode is "Inductor" Diodes should be used when/across motor circuits as well as solenoid circuits

So ...ac current is a positive that collapses then a negative collapse...and each collapse increases

so a stupid question here -- is a SSR usable in aircraft?

The diodes I have seen always have letters and numbers on them. These numbers must indicate the types, sizes or strengths of the diode. So what "size" and type of diode is appropriate for this application?

I do not understand why the diode is connected between the pos, that activates the coil, and the ignition post if the coil as it is a different circuit and would not be effected. Shouldn't the diode be in series with the positive wire that feeds the coil? My application automotive. Oh, I see you are keeping the solenoid powered by the jumper wire.

diode for DC, resistor capacitor for AC

Actually 4:30 the Diode presents an OPEN Circuit to the reverse current. The open switch means that the Diode has NO connection to Ground so it cannot _"[present] a short circuit"_ to Ground nor to any other node. 4 years of it in college then I switched to Software.

Backfeed

Why because you may encounter a Voltage Drain . So to prevent that we use a Diode

Totally incorrect on your explanation. 1 - The diode does NOT go in series with the ground power lead. 2 - - Where did you get 100 times lager from? YES there is a large Reversed Induced Voltage (RIV). 3 - It is the RIV that you want to ground out. But the diode has to be connected in reverse bias so the collapsing field is in forward bias and grounds out.