Post by thread:sensing a isolated switches

> Use a 6mm Dia toriod as a transformer and drive it from the > pic ports at > high freq. I use this to sense a ptc resistor to measure > heatsink temp. How do you do the measurement? Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Fri, 8 Aug 2003, Wouter van Ooijen wrote: > > Use a 6mm Dia toriod as a transformer and drive it from the > > pic ports at > > high freq. I use this to sense a ptc resistor to measure > > heatsink temp. > > How do you do the measurement? > The current which is flowing in the primary will be proportional with the primary pulsed voltage and with the mutual impedance of the secondary ( secondary inductance reflected in the primary coil) so with the load from the secondary. In my opinion it's an ugly methode. :) I've guess your switches are doing something else too, or just some commands to microcontroller ? How many switches do you have ? If there are many is a wrong ideea to isolate them one by one with transformers. Vasile -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

> I've guess your switches are doing something else too, no > or just some > commands to microcontroller ? yes > How many switches do you have ? varies, 1..8 > If there are many is a wrong ideea to isolate them one by one with > transformers. But I want them to be isolated both from the microcontroller and from each other! These switches are on different machines, probably tens of meters apart. Wouter van Ooijen -- ------------------------------------------- Van Ooijen Technische Informatica: http://www.voti.nl consultancy, development, PICmicro products -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

On Fri, 8 Aug 2003, Wouter van Ooijen wrote: {Quote hidden}> > I've guess your switches are doing something else too, > > no > > > or just some > > commands to microcontroller ? > > yes > > > How many switches do you have ? > > varies, 1..8 > > > If there are many is a wrong ideea to isolate them one by one with > > transformers. > > But I want them to be isolated both from the microcontroller and from > each other! These switches are on different machines, probably tens of > meters apart. > Ok, understood. If the buttons are far away, my sugestion is *one* DC/DC isolated converter with n outputs, where n = button numbers, + one optoisolator for every button, or just a n secondary coil AC transformer. The sensing input may be a simple optocoupler (two IR diodes optocoupler or just one IR diode optocoupler and one external antiparalel diode for direct AC sensing). For more than 10m you'll need at least 2mA in buttons for corect sensing. Vasile -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

Check out http://www.qprox.com They have a 4 channel capacitance measurement IC that can be used as non-contact switches. You then interface to the mirco with 4 IO lines (SDO,SDI,REQ,BUSY) and 1 more if you want to have 2 devices (8 switches). The devices can be calibrated to operate throgh front panels of equipment but not effect each other. Kind Regards David Huisman {Original Message removed}