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diodes ve direction only?


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antonic 
Member - Posts: 14
Member spacespace
Joined: September 14, 2013
Location: Australia
Posted: January 13, 2014 at 6:27 AM / IP Logged  
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?
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 13, 2014 at 6:55 AM / IP Logged  
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?
antonic 
Member - Posts: 14
Member spacespace
Joined: September 14, 2013
Location: Australia
Posted: January 13, 2014 at 7:17 AM / IP Logged  
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?
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 13, 2014 at 7:50 AM / IP Logged  
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.
antonic 
Member - Posts: 14
Member spacespace
Joined: September 14, 2013
Location: Australia
Posted: January 13, 2014 at 4:45 PM / IP Logged  
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:
diodes ve direction only? -- posted image.
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 13, 2014 at 8:47 PM / IP Logged  
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.
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 17, 2014 at 8:41 PM / IP Logged  
Did swapping direction work?
antonic 
Member - Posts: 14
Member spacespace
Joined: September 14, 2013
Location: Australia
Posted: January 19, 2014 at 4:36 PM / IP Logged  
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"!
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 19, 2014 at 10:16 PM / IP Logged  
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.
jstruckman 
Copper - Posts: 465
Copper spacespace
Joined: May 03, 2004
Posted: January 20, 2014 at 1:49 PM / IP Logged  
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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