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'"Selfholding" (OT)'
2000\05\21@120732 by ke

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part 0 775 bytes
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<META content='"MSHTML 4.72.2106.6"' name=GENERATOR>
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<BODY bgColor=#ffffff>
<DIV>Hello Piclisters!</DIV>
<DIV>&nbsp;</DIV>
<DIV>I&acute;m wondering if there is someone who</DIV>
<DIV>can help me with this&nbsp; and both tell and</DIV>
<DIV>show me if it&acute;s possible to do this</DIV>
<DIV>&quot;selfholding&quot; with transistors&nbsp; instead ?</DIV>
<DIV>&nbsp;</DIV>
<DIV>Regards</DIV>
<DIV>&Aring;keN</DIV></BODY></HTML>

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2000\05\21@124059 by Jim P

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How 'bout an "SCR" -

Once 'fired' it is on till power is removed ...

SCR a three terminal device: Anode, Cathode and Gate.

Postitve (current limited) voltage applied to
Gate wrt Cathode and the device will conduct
from Anode to Cathode.

SCR is 4-layer NPNP device "configured" internally
as a pair of transistors that keep each other on once
turned on.

Jim

----- Original Message -----
From: ke
To: spam_OUTPICLISTTakeThisOuTspamMITVMA.MIT.EDU
Sent: Sunday, May 21, 2000 10:58 AM
Subject: "Selfholding" (OT)


Hello Piclisters!

I«m wondering if there is someone who
can help me with this  and both tell and
show me if it«s possible to do this
"selfholding" with transistors  instead ?

Regards
keN

2000\05\21@184904 by paulb

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ke Neehr wrote:

> I«m wondering if there is someone who can help me with this and both
> tell and show me if it«s possible to do this "selfholding" with
> transistors instead ?

 As ever, a bit more info on what you want to do with it might make it
easier to suggest an optimum solution.  A thyristor = "SCR" would likely
be one easy way to do it.

 Note that a thyristor is just like a transistor; you either use it in
common cathode mode with the load in the anode side and a current limit
resistor in series with the switch to the anode supply, or in common
anode mode with the load in the cathode side to negative, in which case
the switch (pushbutton) goes directly between gate and anode.

 Two other things, also like a transistor you generally have a resistor
between cathode and gate to prevent spurious tripping, and a clever way
to turn it OFF using a normally open switch, is to put the switch
between cathode and anode.  Pressing the switch holds the load on, but
when it is released, the thyristor has ceased conducting.

 You know that it is just lack of time that prevents me answering all
your enquiries - if you need circuits to the above, I will have a go at
drawing them...
--
 Cheers,
       Paul B.

2000\05\21@185055 by paulb

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Oh yes, the other oddity of ke's circuit was that the lamp was across
the switch rather than across the relay.

 Was it really supposed to be across the relay?
--
 Cheers,
       Paul B.

2000\05\22@041044 by Nebelong Bjarne

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part 0 286 bytes

Hello Piclisters!

I«m wondering if there is someone who
can help me with this  and both tell and
show me if it«s possible to do this
"selfholding" with transistors  instead ?

Regards
keN

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2000\05\29@105403 by Alok Dubey

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scr would be the best or u can implement the same using gates..
but remember if u r driving AC , commutation is a major pain..
Alok


   

-----Original Message-----
From: ke [.....neehrKILLspamspam@spam@SWIPNET.SE]
Sent: Sunday, May 21, 2000 4:58 PM
To: PICLISTspamKILLspamMITVMA.MIT.EDU
Subject: "Selfholding" (OT)


Hello Piclisters!

I«m wondering if there is someone who
can help me with this  and both tell and
show me if it«s possible to do this
"selfholding" with transistors  instead ?

Regards
keN

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