Post by thread:"Selfholding" (OT)

part 0 775 bytes <META content=text/html;charset=iso-8859-1 http-equiv=Content-Type> <META content='"MSHTML 4.72.2106.6"' name=GENERATOR> </HEAD> <BODY bgColor=#ffffff> <DIV>Hello Piclisters!</DIV> <DIV> </DIV> <DIV>I´m wondering if there is someone who</DIV> <DIV>can help me with this  and both tell and</DIV> <DIV>show me if it´s possible to do this</DIV> <DIV>"selfholding" with transistors  instead ?</DIV> <DIV> </DIV> <DIV>Regards</DIV> <DIV>ÅkeN</DIV></BODY></HTML> </x-html> Attachment converted: creation:self.JPG (JPEG/JVWR) (000153BD)

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_OUTPICLISTTakeThisOuTMITVMA.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

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.

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 Attachment converted: creation:selfhold.gif (GIFf/JVWR) (000154D5)

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 [.....neehrKILLspam@spam@SWIPNET.SE] Sent: Sunday, May 21, 2000 4:58 PM To: PICLISTKILLspamMITVMA.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