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The diagram above shows the proper arrangement of a kickback diode and the correct flow of electrons in such a circuit. There is no short because the control switchis open and there is no path to the positive battery terminal, the only flow is "around" the coil and kickback diode.
If the arrows are taken to mean current flow and not electron flow they are backwards but the diagram and the circuit itself is still correct.
My LH diagram obviously shows the electron flow from negative to positive thru the coil and the switch. The negative terminal of a battery is called the "negative", because it has an excess of negative electrons at that terminal. The electron "flow" in a circuit is from negative to positive because the electrons will flow from the battery post with excess electrons to the post that has a deficiency of electrons. That's what batteries do! A charged battery will "push" the electrons in the battery toward the "negative" terminal.
IHBD, would you please explain your formal electronics education background? Your Personal Profile doesn't provide any clue. You obviously haven't tried my experiment.
I was hoping we wouldn't get into an argument about whether "electrons" flow, or "holes" flow. That's a bit advanced for this discussion. If your brain works better with "conventional current", the circuits will be the same, but the technical description about how "current" flows is actually harder to explain. That's the same as "hole flow" theory. Electricity "flows" at about 1,860 miles per second, so it doesn't much matter which way you think about it.
Last edited by Hot Rod Roy; Apr 13, 2020 at 02:05 AM.
Diodes have 2 functions, limit the amount of current that can flow through them and limit the direction it can flow through them.
seat diode I'm figuring it may have been a recall fix by GM done by dealership. But could not it have been put at a safer location. I just got the car a few weeks ago after it had been sitting up for a good while and figure inserting the seat belt into the latch which( is a pain anyway) is located right next to the panel where the diode is behind cause the problem. Had no problem till after putting on seat belt a few times then noticed controls not working so check fuses and noticed circuit breaker was extremely hot.
Post #11, and someone finally gets it!! The GM engineers aren't so stupid that they'll throw a diode into the wiring just to frustrate the amateurs.
Here's a diagram to try to explain it:
When an inductive component ( relay, solenoid or motor) is active, current flows thru the component. When the switch (or electronics) opens in order to stop the current flow and turn off the component, the inductance of the component will force current to continue flowing because of the collapsing magnetic field in the component. If you have a diode in parallel with the component (like my diagram), the current caused by the collapsing magnetic field will flow thru the diode, rather than causing a spike in voltage at the switch. That spike in voltage will cause a spark in the switch, which shortens the life of the switch. The diode is there to lengthen the life of the switch. (Good engineering!)
You can do your own experiment if you want to see proof for yourself! With 12 v. battery and a solenoid, but rather than using a switch, touch the two wires together to actuate the solenoid. Watch for a spark as you move the two wires apart, as if you're opening a switch. You MUST use two wires that you can touch together in order to see the spark, not a switch! Now put a power diode (1N4001 or equiv.) in parallel to the solenoid (like my diagram), and repeat your test. Hmmmm . . . no spark!
HRR, it has been a long time since I dealt with electronic theory in my career so I need an update. I understand electron flow vs conventional power flow. In your diagram, the left hand sketch shows the creation of a magnetic field and direction of electron flow. However, in the right hand sketch, with the control switch open and the magnetic field collapsing, does not the flow in the coil reverse and go in the opposite direction from the arrows indicated? I no longer have my theory books.
In the right hand sketch, with the control switch open and the magnetic field collapsing, does not the flow in the coil reverse and go in the opposite direction from the arrows indicated?
No. The inductance of the coil causes the current to continue flowing in the same direction as the magnetic field in the coil is collapsing.
https://www.electronics-tutorials.ws.../inductor.html
If we now close the switch (t = 0), a current will flow through the circuit and slowly rise to its maximum value at a rate determined by the inductance of the inductor. This rate of current flowing through the inductor multiplied by the inductors inductance in Henry’s, results in some fixed value self-induced emf being produced across the coil as determined by Faraday’s equation above, VL = Ldi/dt.
This self-induced emf across the inductors coil, ( VL ) fights against the applied voltage until the current reaches its maximum value and a steady state condition is reached. The current which now flows through the coil is determined only by the DC or “pure” resistance of the coils windings as the reactance value of the coil has decreased to zero because the rate of change of current (di/dt) is zero in steady state. In other words, only the coils DC resistance now exists to oppose the flow of current.
Likewise, if switch, (S1) is opened, the current flowing through the coil will start to fall but the inductor will again fight against this change and try to keep the current flowing at its previous value by inducing a voltage in the other direction. The slope of the fall will be negative and related to the inductance of the coil as shown below.
Current and Voltage in an Inductor
It's that +VL spike in voltage at the time the switch is opened that will cause the arc to develop in the switch. That arc in the switch will decrease the life of the switch, unless a diode is installed to conduct that surge of current and voltage away from the switch. The -VL spike is across the inductor, so no spark is created.
It is unlikely it is a ground issue if they are all grounded together and the rest of the seat motors are working. if it is a simple DC motor for the lumbar suppport, you can hotwire it to the battery and see if it works.
Originally Posted by Red 91
How do we know the lumbar pumps are in working condition? post 13
Brought a power supply home from work and hooked both sides to 12v. Both worked.
No. The inductance of the coil causes the current to continue flowing in the same direction as the magnetic field in the coil is collapsing.
It's that +VL spike in voltage at the time the switch is opened that will cause the arc to develop in the switch. That arc in the switch will decrease the life of the switch, unless a diode is installed to conduct that surge of current and voltage away from the switch. The -VL spike is across the inductor, so no spark is created.
Thanks. I got reading to do when I get home. Guess this lockdown I'll be in for 2 weeks will be good for something.
