![]() You could also build a multiple-neon lamp, but the lamp firing voltages are different enough that individual current limiting resistors must be selected for each lamp. This lamp operates from a 12V AC wall transformer and the “bars” are much clearer than with an incandescent light. ![]() As you can see, the circuit is simple and the wiring is not at all critical. A circuit diagram with parts lists follows in Fig. You can use a neon “nightlight” (Photo 6), but it’s rather dim so it’s not too useful unless the room is dark! Better lamps are available.įor my use I built a multiple-LED lamp (Photos 7A and 7B). Neon lamps and white LEDs operating on AC power work well because both produce pulses of light even though your eyes can’t really see the pulses, at least not with 60Hz power. You can see the stationary appearing bars, but their edges look fuzzy, so it’s difficult to set the speed “right on.” The phosphor coating on the inside of the tube continues to radiate light between the AC power cycles. The filament does not cool very much between cycles of the AC power so the light output is rather constant. Incandescent lamps (ordinary light bulbs with a filament) work, but not too well. Figure 1 shows an example printout from strobo.exe: the outside diameter of the bars is over 7", which makes it easier to see whether the bar edges appear stationary. The zip file, strobe.zip, contains both executable programs with documentation. It will print up to five strobe bands on a single sheet but the bars are a bit “jagged.” Both programs are available for free from several websites, including the TDL site(5). There are two public domain programs: one is named strobe.exe and it’s an MS-DOS program which will run under Windows. These days it’s not necessary to buy a stroboscope disc if you have a computer, because you can easily print your own for any speed and for either 50 or 60Hz power. It automatically captures the last speed, the maximum speed, and the minimum speed. After a ten-minute or so turntable warmup, press the DIGIstrobo’s memory store button. You can also use the device to measure speed stability. You can check the speed while playing a record if you provide something for the DIGIstrobo to “see.” A small piece of reflective tape on the turntable edge will work, and a supply of tape is furnished with the unit. The published accuracy is ☐.05% (or 0.1 RPM). Hifi4music(4) markets the DIGIstrobo, which is a rotational speed measuring device adapted to audio use that is, it directly reads and displays the turntable speed so it can be used for all records from 33 1/3 to 90 or higher RPM.
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