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Registered Member #1430
Joined: Sun Apr 06 2008, 11:12AM
Location: Ã…rhus, Denmark
Posts: 102
hey all, i have been looking for an automatic switch(for low voltage capacitors) that wont let any power trough until it reaches a certain voltage, then when it reaches the correct voltage it will keep conducting until the capacitors have discharged. any suggestions on how to do this? sorry for poor grammar (im posting from a psp)
Registered Member #311
Joined: Sun Mar 12 2006, 08:28PM
Location:
Posts: 253
depends what you mean by 'discharged'.. A SCR would be the obvious choice, but you'd need to arrange a trigger at teh required voltage, e.g. with a comparator, voltage detector IC (e.g. MCP100), or sidac for higher voltages (100s)
Registered Member #690
Joined: Tue May 08 2007, 03:47AM
Location: New Jersey, USA
Posts: 616
Yes, I would agree with Avi. A DIAC or SIDAC seems to be the obvious choice here. They are nicknamed "solid-state spark gaps" because thats exactly what they do. At a certain voltage they instantly allow current flow and then shut off when current stops.
Registered Member #1430
Joined: Sun Apr 06 2008, 11:12AM
Location: Ã…rhus, Denmark
Posts: 102
there is only 1 electronics store where i live and they don't sell sidacs, the only diac they sell is a 32volt, i need about 3-5. i have no idea what they do but could i use a thyristor a triac or maybe a Varistor?
Registered Member #514
Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295
Depending on your application, I'd say a comparator should do it. Have it trigger a thyristor and you're set. Cheap and you can get the parts anywhere.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
You don't need a DIAC/SIDAC/SHOCKLEY diode, just a zener will do because once the gate current has triggered the thyristor it can be removed, the thyristor will remain 'on' for as long as the anode-cathode current remains above the "holding current"
Registered Member #1430
Joined: Sun Apr 06 2008, 11:12AM
Location: Ã…rhus, Denmark
Posts: 102
so i need a zener and a thyristor? im kinda new to this, could you tell me what rating those should have and how to connect them? im running a 3v(or so, motor on solar charged capacitors with with 47000uF)
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voltage controlled discharge?
