> I need to turn on a couple of small security monitors when a TV is = > turned on. In the past, they made a gizmo for the early personal = > computers that turned on the monitor, printer, etc. when the computer = > was turned on by sensing the current being drawn by the computer. I = > have not seen them for years. > > It would be trivial to open the TV and find some voltage in there only = > present when it is on and let it activate a relay, but when the TV dies, = > I would have to go through the procedure again. A universal device with = > a plug-in for the TV would be nicer, and would not require cracking open = > the TV. I think modern TVs draw a little line current all the time, so = > this thing would have to distinguish between a fraction of an amp, and = > the higher draw when the TV is actually on. > > Any suggestions for a simple circuit? Or is there a commercial product = > that will do the job?
6 components, is that small enough? In series with one of the mains leads 1 resister delivering 0.7V at trip current. In parallel with this resistor 2 high voltage bipolars: 1 NPN, 1 PNP, both emittors to the mains side, both bases to the load side. collector of PNP to anode of a 1N4007, collector of NPN to kathode of a second 1N4007. Connect the other sides of the diodes (one kathode and one anode) to each other and to the coil of an AC-relais. Other side of relais coil to the other mains pin. The relais can be replaced by a resistor and a triac. (1 component more) That's it. Harry -- Author: H.C. Croon INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
