Triacs

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rish27

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This might seem somewhat basic but I am a little confused. I have been told that the terminals of a triac MT1 and MT2 can be used interchangebly. However , I was developing a lamp dimmer circuit today using a BT 139 - and this does not seem to be the case. The dimmer works only in a specific way. Any comments ?
 
It works either way, but it can be turned on only between gate and one of it's anodes, so you need to keep Gate to Anode voltage and change current direction and it will work.
 
rish27 said:
This might seem somewhat basic but I am a little confused. I have been told that the terminals of a triac MT1 and MT2 can be used interchangebly.
Click to expand...

Yes, but with different gate triggering sensitivity. For example the gate current can be 5mA and 13mA for a typical TRIAC in the above cases. Your circuit may not be able to provide the required gate triggering current.

So, given sufficient drive current, it can work.
 
That's right, I never liked triacs
 
Jay.slovak said:
That's right, I never liked triacs
Click to expand...

No problem. They don't like you either. :lol: :lol:

Ah Jay, just let you know the printer port parallel PIC programmer link in the sticky does not work anymore.
 
Thanks everyone - but I'm still puzzled - since it is AC why should it make any difference which way the two anodes are connected?

If I connect MT1 directly to the load it does not work. However when I connect MT2 to the load the dimmer works.

Any leads?
 
Meaby eash side is difrent.

Like transistors if you go an stick a cuple of them in your multimeter each one will have difrent gain.Probobly this hapends here too (Since these things are made up of transistors)
 
Such a good joke ROFL :lol:

Thanks, I will correct the Sticky.

EDIT: Sticky corrected
 
rish27 said:
Thanks everyone - but I'm still puzzled - since it is AC why should it make any difference which way the two anodes are connected?
Click to expand...

Because the physical gate location is not symmetrical in the structure of the TRIAC construction. It is closer to MT1 so less current is needed to trigger the conduction of the TRIAC than the other cases.
 

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