Diode direction?

Is this correct according to the diagram explaination?

Yup!

Easy way to figure it is the line goes towards the alternator. My self I use the radio shack part #276-1661. They are way over kill and cost around $2.50 for a pack of 4

Yes. Flow is in the direction of arrow. Stopped
against the line. Just make sure no voltage can
come out of the wire going to the starter terminal.
(assumes bypass surgery) I gave no polarity because
the situation is reversed if there is positive
ground. Put the diode on the wire, leave it off the
starter. Use a test light and turn on the ignition.
If the test light lights on the diode terminal you
will attach to the starter, it is wrong. (also
assumes a good diode) Jim

The left side of the diode is the cathode and the right side is the anode. Electrons flow from cathode to anode, which means, the cathode will be connected to the negative side of a battery or the black wire on ohmmeter and the anode will be looking at the positive side of the battery or the red side of an ohm meter before electrons will flow. Reversing polarity and nothing will flow if the diode is good. You can confirm that with an ohmmeter. Infinate resistance when the red wire is on the cathode and the black wire is on the anode. TRY IT and you will see.

Some think the flow is reversed. And in a way, if you go with current flow theory, current flows with the arrow, electrons flow against the arrow. Hope this helps.

"Some think the flow is reversed. And in a way, if you go with current flow theory, current flows with the arrow, electrons flow against the arrow. Hope this helps."

George my man you did good till you added this sentence. There is electron movement and there is the "absence of electrons referred to has holes".

Electrons being negative charges are attracted by a positive voltage. Hence if you want the diode to conduct electric current (electrons) you forward bias the diode with the most positive voltage on the Anode...the right side of the picture.

If you are a college boy you are taught "hole flow" which is just the opposite of electron flow for direction and polarity. The hole is merely the "hole" developed when the electron moves down the line. The electron goes to the + terminal and the holes migrate in the opposite direction to the negative terminal.

Having been to both schools, I found that if you are fixing something that has already been designed then electron theory is the way to go about it.

However, if you are an electronics equipment designer, hole theory is more convenient as it works from the power source out to the load whereas with the electron theory, electrons are sucked back to the power source and you approach it from the opposite direction.

HTH,
Mark

I understand "Yup". lol.


I'll put the voltmeter to it tonight and "TRY IT". I'm getting a better understanding.


Fellas, I REALLY appreciate the help! Thank you!

Word of caution. The reading depends upon the way the battery
is hooked up within the meter. Some meters don't have the +
side of the internal battery connected to the Red lead on the
Ohms function. So don't "get your shorts in a knot (to
paraphrase Dave2)" if you get conduction with the Black lead on
the anode. I have had both.

Really it's a moot point. If the diode symbol isn't stamped on
the side of the diode, there will be a ring on one end signifying
the cathode.

A good diode will show some conduction in one direction and
infinity in the other. Anything else warrants a bad diode. So pay
attention to the reading, not which color lead is connected to
which part of the diode. Course if you have a meter with a
squeaker in it, it should only squeak in one direction.....they call
the scale "Diode Check" or something to that effect.

HTH,
Mark