diodes ve direction only?

Are there any diodes or component out there that only allows -ve signal to flow through and not allowing any other signals through nor back?

Standard diode allow +ve one way and -ve the other way, I'm after -ve direction only, nothing else through nor back?

Hmmmm....

Yes, diodes only allow current to flow one way - ie, "conventional" in the direction of the arrow (or out the line end).
That is equivalent to "electon(ic)" current flowing the other way, but don't worry about that. (I have seen even experts question whether "current" is +ve (ion) flow (ie, conventional) OR "electron" (or -ve ion) flow. I do have words for dorks like that, but this site will censor them.)

That diode conventional current direction is true for all electrical signals whether AC or DC - excluding frequency limitations, voltage drops, and exceeding specs (voltage or current).


Do you mean 'other signals' as in frequency filtering, or voltage/current magnitude filtering?

Sorry, "other signals" mean +ve signal...

I can't have +ve signal coming back...I can only have -ve signal one way and nothing else either directions.

Is there such a diode/component that can do this?

Yes - a diode.

See the Diode section above, or google diode (circuits) etc.


FYI - Unfortunately the first ref returned in my google (diode(s in) circuits) was allaboutcircuits - Introduction: Diodes And Rectifiers whose diagram is misleading (arrows the wrong way) because "Arrows indicate the direction of electron current flow.".

I suggest you forget about "electron" flow and stick to "conventional current" - ie, current moves from +ve to -ve thru a circuit.


[Geez - electricity is not electron flow. In simple terms, electrons (or ions etc) flow as a result of electricity - it is not the flow itself that is electricity.

Standard diode will not work as it allows +ve current to flow from Anode to Cathode.

I need a diode that doest NOT OUTPUT when this happens. See red circle below:

Easy - change its direction.

If that doesn't work I think it's time you describe what you are trying to do or provide a diagram/circuit.

By the sounds of it you want an OC - aka Open Circuit - which is a very high resistance made out of air or some other high dielectric/insulating material.   
But I suspect you are merely a bit confused with how a diode works, else what can be achieved by a simple passive component.

Did swapping direction work?

No, that won't work either....

I just wanted to allow -ve to flow one direction and nothing else backwards or forward.

I've worked out a different way to tap into the stock folding mirrors. Thanks so much for you help "oldspark"!

Again, a diode will do that.
-ve in one direction is the same as +ve in the opposite direction.
That Cathode output you circled is +ve output, not -ve output.

If you still don't understand, explain your application and I will explain why a diode will work.

I diode will not do that. Antonic wants negative to go one direction, and no -ve and no +ve to come back through. A diode will still allow +ve to come back through. That is why he has the red circle on the diode showing +ve still coming back through.

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That is called an open circuit which is even cheaper than a diode.


A diode let's -ve current flow one way and +ve current the opposite way, and neither the other.

-ve one way & +ve the other means exactly the same thing.

To block one and not the other requires a quantum membrane, but that is of no use in an electical circuit.


The diode pic with antonic's circle is electrically exactly the same as the one below it with -ve flowing from left to right.
So if the -ve flowing from left to right is acceptable, why isn't the one he circled?


YET AGAIN, give and example or a description or a circuit/sketch of what is to be done.
Or try a diode in the circuit application and THEN tell me it does NOT work.

jstruckman wrote:

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I diode will not do that. Antonic wants negative to go one direction, and no -ve and no +ve to come back through. A diode will still allow +ve to come back through. That is why he has the red circle on the diode showing +ve still coming back through.

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Spot on.

I was tapping into the side folding mirrors with another switch so I couldn't allow +ve to flow back into my circuit.

I've now found another way to do this...


Thanks all!

Pray tell, how?

A diode will do it. Unless you mean you needed two diodes - ie, one for your tap plus one inserted into the existing feed.


It can be done with a relay, but diodes are usually used instead for simplicity.

And as I said, why did you only circle ONE of those diagrams when the one under it is exactly the same? (But deals with -ve flow.)


And people wonder why I tell them only to worry about conventional current flow and not worry about electron or ion flow. It's ok once you master the basics, tho even then I have seen experienced experts get confused - viz the text book author that wanted to know if "electricity" was the flow (sic) of +ve charge OR -ve (electron) charge where OR meant else implied one OR the other but not both. Poor fool.

FYI - I referred to this thread in another reply so if you can justify your actions or reasoning... (That's for both antonic & jstruckman. I'm referring especially to antonic's last reply above.)