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Hi Ed,
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A stroboscope or LED Strobe like you made (great idea!) has so much in common with an oscilloscope that I knew I had to get a Strobotac after seeing how it brought repetitive mechanical motion to a standstill in front of my eyes. This is exactly what an oscilloscope does. Since, you showed a few pictures of your LED Strobe oversampling the spinning router bit it is worth mentioning there is a direct analogy to how digital scopes work. As long as the digital scope can sample repetitive mechanical motion twice as fast as the period of the motion there will be few problems understanding the results. This corresponds to the Nyquist Theorem where you are sampling at faster than 2X the period of the waveform being sampled. But when the LED Strobe's sample rate is less than twice the rate at which the sample is vibrating or turning you are going to get aliasing results that can lead to erroneous conclusions about what your sample is doing. This all becomes perfectly clear right in front of your eyes when you can vary the strobe's speed and observe the effect it has on what you see. Dennis Tillman W7pF -----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Ed Breya via groups.io Sent: Saturday, June 27, 2020 4:44 PM To: [email protected] Subject: [TekScopes] OT: Strobe lights - just a suggestion, no discussion needed In the recent thread about variacs, there was a tangent off to strobe lights. Barry wrote: "Coincidentally, I've been looking at getting one of those over the last few days. Unfortunate what the bulbs cost for them these days. I suppose if I watch long enough..." You can get or build "modern" strobe lights based on high power lighting type LEDs, and not have to worry about the xenon lamps and powering them and controlling them. LEDs are much easier to deal with, and with modest voltages. A few years ago I did some experimenting with LED strobing as an attachment to my coil winding machine project. I think I reported it here in the photos section. If I can find it easily, I'll post a link. Anyway, with just a small (6-12 LED cluster, don't recall exact size) warm-white LED module from a lighting fixture, I got decent viewing with normal ambient light, and had no trouble looking in detail at a router bit spinning around 25,000 RPM. I had planned to (eventually) build a scaled up general purpose version with a large LED array. I have the rough design and parts set aside, but it's a low priority, since I don't often need a strobe, and I have a nice old regular Xe one that I had fixed at about that time too. If the repair of the old Xe had not turned out so easy - the flash head capacitor was shot , and had an intermittent wire - I would have probably junked it and built the LED version. The xenon lamps have the edge in terms of peak power for a single device, but the LEDs win in terms of rep rate and pulse width control, and color temperature choice. The LED peak power (drive current) is limited to maybe 3-10 times normal, so you need lots of them for high brightness. They are easy to scale up in number, and I'm convinced they can way outperform xenon lamps for strobes. Anyway, I believe there are by now lots of commercial LED-based strobes out there, yet another solid-state replacement of a "tube" technology. Ed -- Dennis Tillman W7pF TekScopes Moderator |
