I'd think a diode, white LED and a resistor would make a good enough strobe. Maybe 2 resistors to isolate the AC lines enough a little better. Dwight
________________________________ From: Tony Duell via cctalk <cctalk@classiccmp.org> Sent: Wednesday, November 6, 2024 8:39 AM To: General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> Cc: Mike Stein <mhs.st...@gmail.com>; Tony Duell <ard.p850...@gmail.com> Subject: [cctalk] Re: Running DOS executables on other versions of DOSRe: Looking for Sharp PC-5000 disk drive (CE-510F or possibly MZ-80B) On Wed, Nov 6, 2024 at 4:31 PM Mike Stein via cctalk <cctalk@classiccmp.org> wrote: > > I use a strobe disk glued to a fridge magnet that I stick on the spindle > motor of 5 1/4" drives to confirm the speed; the trouble is that it's > becoming difficult these days to find lamps that emit light at 60 Hz. ;-) I made a simple circuit (3 common TTL counter chips, a couple of transistors, a 4.91...MHz crystal oscillator module, 7805 regulator and a few passive components) that flashes 4 white LEDs either 100 or 120 times a second wth a 1/16th duty cycle. It runs off a 12V DC supply This will simulate a mains lamp for such a strobe disk, and of course can be used on either '50Hz' or '60Hz' markings no matter what your mains frequency is. The crystall osciltor module is easily accurate enough for setting up such motor speed controllers. I'd be happy to share the schematic but of course I can't post it here. If you want to avoid electronics, then stroboscopic tuning fork? -tony
