Or indeed a 78xx device, you've just reminded me of a job I have to do. On Sat, 29 Jun 2019, 19:21 Jon Chandler, wrote: > How about configuring an LM317 as a constant current source powered from = a > 9 volt battery with an LED in series to drop some voltage and to indicate > current flow? > > On Sat, Jun 29, 2019, 3:48 AM AB Pearce - UKRI STFC < > alan.b.pearce@stfc.ac.uk> wrote: > > > >I guess I could probablly jerry-rig something with some 4mm shrouded > > sockets, > > > a red LED a 9V battery and a resistor, I'll probablly do that if I > don't > > get an off the shelf solution. > > > > > > You don't need shrouded sockets - or are you looking at using standard > > multimeter leads as your probes? > > > > I would knock it all up on a piece of veroboard with a pair of brass > wires > > as probes. I would add a push button and zener to ensure the red led > > doesn't light on the current of a reverse LED. > > > > So from battery have switch, resistor, zener to battery return (voltage > > chosen to be a little higher than forward voltage of red led plus LED > under > > test) then red LED and LED under test to battery return. > > > > Without the zener an LED under test may provide enough reverse breakdow= n > > to light the red LED, but such reverse breakdown would hopefully be at = a > > voltage somewhat higher than the worst case forward voltage drop. If yo= u > > want to be pedantic another LED in series with the zener gives a 'fail' > > indicator, so one LED should always light when the button is pressed - > > helps with testing by non-technical people. No meter needed. > > > > > > > > > > > > -- > > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > > View/change your membership options at > > http://mailman.mit.edu/mailman/listinfo/piclist > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .