Zener Diodes - No !

[sj-bradley]

The circuit you have drawn will only allow current to flow once the junction between all the diodes reaches AT LEAST 15 or 18 volts. Once that has been reached or exceeded will the voltage and current begin to rise on the Tach side.

 

It's basically being used as a voltage limiter to stop high voltages and current surges entering the tacho and destroying it.

 

When you switch the coil (an inductive load) you get HUGE reverse voltage spikes which this zener is protecting you from. When either coil 1 or coil 2 goes +ve (an effect from the self induction when you open the circuit), it can reach hundreds of volts. The 1n4001 diodes let this through to the junction (the other 1n4001 blocks it from going back to the coil) and the zener breaks down when 18 volts is reached allowing a small pulse through to the tacho. Once the voltage drops below that threshold again, the zener blocks it again.

 

So this zener "leaks" once the breakdown voltage is exceeded.

 

Simon.

[sj-bradley]

_{Here is a simulation run demonstrating that circuit.}

 

 

The red line is the output from the coil going +- 50 volts around zero volts. The blue line which almost overlays the two high red peaks and you can just see on the zero line between these peaks is what a diode does.

 

The green line shows that the zener does not conduct until the blue line goes above 18 volts and there is always an 18 volt difference between them. One the blue line drops below 18 volts, the zener stops conducting.

 

(And I can hear the smirking about those humps - so stop it at the back there - Yes - YOU laddie ...)

 

Simon.

[Al Milton]

It's still black magic and witchcraft to me Simon.

 

But it's good to know there are always more informed/knowledgable brains to call on if required.

[sj-bradley]

Thanks.

 

There are still some electronics components that even I am still learning about. Tunnel diodes, varactors, gyrators etc. And, yes, those are genuine names I found in electronics books.

 

As for atomic physics, I swear that when they ran out of Greek names, they started making them up. Quarks can have spin up and down, colour, charm, strangeness.

 

I mean Look at this I found on the net ...

"There are six types of quarks, known as flavors: up, down, strange, charm, top, and bottom.^[4] Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process ofparticle decay: the transformation from a higher mass state to a lower mass state. Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators). For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties have equal magnitude but opposite sign."

 

So a quark can have a strange charming bottom. Hmm, That could be an interesting pick up line ...

 

Told you professors can be nutty !

Simon.

[Guest 2b cruising]

Seems your half way there Simon. LoL. Do you have the Delorean in your garage?

[Snapperpaul]

Stop showing off

Believe it or not we discuss a lot of stuff at the pub on Sunday's mostly a surface understanding and gets quite beer fueled

My cousin knows Alan Bond and has connections with the BIS, Icurus Interstellar and Daedalus

Who showing off now.

Here's a photo I took many years ago ( just look at the haircuts) a similar experiment was seen on a recent science program but this was about Quantum packet encryption

 

[Guest 2b cruising]

Isn't that Simon on the left?

[sj-bradley]

Oh, that's just left over junk I can remember.

 

Seems like the more complicated the ideas in you head, the shorter the time you can remember them. Kind of like radioactive decay 1/2 life. The more active, the quicker it disappears.

 

I mean you can remember where your cars keys are for AGES, but more complicated ideas like "whose round is it" or "Wife's anniversary" being so complex, vanish within minutes ...

 

Simon.

[Shaft]

Sod the quantum physics, you've discovered the cure for Insomnia!

 

Edited May 13, 2015 by Shaft