Hi Old AM radio works fine as a cheap and cheerful RF radiated field detector. That was what they were designed for all those years ago. You will be surprised by the number of source radiators around a typical house or workshop. On Fri, Dec 16, 2011 at 9:58 AM, Philip Pemberton wr= ote: > On 16/12/11 07:42, Electron wrote: > > Nice (although quite distressing for You ;( ) experience, thanks for > > sharing. Just curious..: if the board was in a metal box, with a wire > > going from circuit ground to the metal box, would (when the box was > > closed with a metal lid) the circuit have behaved well even with the > > lamp on? > > If it was in a grounded tin box (Altoids tin?), it probably would have > worked fine... > > > (sure there are possibly still wires going out and acting like antennas= , > > but given the very low frequences emitted by the lamp, this should not > > pose a problem) > > It sure screwed up the sense amp! > > I tweaked a few component values (reduced resistor values in the > feedback loop) which has mostly eliminated the effect. > > Anyway -- this is all part of a battery analyser. I'm basing the charger > logic on the Atmel AVR450 appnote (and a similar Microchip appnote whose > ID# I can't remember at the moment) but redesigning the switchmode power > supply. AVR450 has a bit of a... "reputation". Specifically, the FET > gate driver falls over at high frequencies, and usually ends up blowing > the drive FET outright, or running it in a linear mode and cooking it. > > My "V2.0" design is based on a SEPIC converter, a National Semi > synchronous gate driver and a pair of FETs. "If it's worth doing, it's > worth OVERdoing." > > Then there's the discharger and relay driver to deal with... Ideally I > want some kind of reverse-polarity protection on the relay driver -- if > the battery is hooked up backwards, the O/P relay will refuse to switch > over. That's a job for later though... mainly because I can't think of a > sane way to do it. > > -- > Phil. > piclist@philpem.me.uk > http://www.philpem.me.uk/ > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .