I can't get SCR's to work

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Has anyone been having issues with SCR's (silicon controlled rectifiers)?

I've been trying a couple of different ones, and they just won't work for
me!

I've viewed some schematics with SCR's in them, and it seems you can just
connect them up like transistors... seems simple.  A resistor connects to
the gate of the SCR, and you connect a load (such as an LED).  So why
wouldn't they work?  Is there a trick to it?  I've tried connecting them
both ways and still nothing.

I am using a 12V supply.  I've tried various resistor values (for the gate)
such as 10K, 2K and 1K.  Attempting to trigger it fails.

I've tried a couple of SCR's from Jaycar Electronics, namely the C106B and
C106Y.  I can't even get an LED to light up!!   Can anyone make a
suggestion?  It seems I am just wasting money on these dumb devices.
Thanks.
                                              +
                                               |
                                            LED
                                               |
                                              [] 560R
                                               |
Trigger (+)  -----====------SCR
                        Resistor           |
                                               |
                                               -




Re: I can't get SCR's to work



"Jason S"
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 **  You real sure you know where the Anode, Cathode and Gate leads are ??



............  Phil



Re: I can't get SCR's to work


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gate)
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Here's an example test circuit - what you are doing seems to be correct
though maybe the resistor value is incorrect. I don't have the data sheet
for yours on hand, but the circuit referenced gives 270 Ohm as the resistor
value. Have you tried one that low?

Ken



Re: I can't get SCR's to work


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2 things I can think of -

1) is the SCR and LED connected the right way around?
2) is the current drawn by the LED sufficient to latch the SCR on?

Try this circuit below it should show you if the SCR is working.  Use a
normally open push button switch to trigger the SCR and once triggered the
12V globe should continue to illuminate even after the trigger voltage is
removed.


+12V --------------------
            |                          |
            |                          |
            |                    12V 6W globe
            |                          |
            |                          |   anode
           /                        -----
           \ R                      \   /
          /                            -
          |                   gate / |  cathode
          |        _|_           /   |
-        -------   --------   |
                 switch

R = 270 ohm



If this circuit works then the problem with your LED circuit is either
component polarity or insufficient current draw.




Re: I can't get SCR's to work



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thanks guys. its fine now.

Jason.



Re: I can't get SCR's to work



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(snip)
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Fess up, wot'd you change?

Re: I can't get SCR's to work



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well i didn't realise the SCR's anode, cathode and gate are in different
order compared to that of a transistor. I always assumed the gate was the
middle pin. Ha ha.  I laughed it off, but I'm relieved now. I've never
worked with SCR's before.... First time for everything!! ;-)



Re: I can't get SCR's to work



"Jason S"

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  **   So you were starting from SCRatch  ??




...........  Phil



Re: I can't get SCR's to work



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u could say that.
Jason.



Re: I can't get SCR's to work


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Tranny with an anode, cathode and gate??  :-)

You'll find that transistors have their pins in different orders as well.
Some will be Collector, Emitter, Base whilst others are Collector, Base,
Emitter... and so on..

Sounds like you could make use of a transistor reference guide that has the
pinouts included.....





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