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  • cgosh commented on 0xyJin's instructable Leveling Laser Cutter Z-table4 months ago
    Leveling Laser Cutter Z-table

    Drawings no. 2 and 3 suggest the black belt was not taut. If there's no simple way to tighten the slack, you could add an idler pulley anywhere, either pressing inward or outward.

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  • How to customize skateboard grip tape (laser cutter)

    I just bought a 2500mw hobbyist laser cutter for $250 from GearBest.com. It should do jobs like this (bed size is about 12" x 15"). Requires a Windows PC/laptop. A membership at a tech shop (find them at MakerDirectory.com, then click Makerspaces link for about 100 locations) is typically around $100/month, but I've seen them for $50/month ( i3 near Detroit, for example). You'll get access to any equipment you qualify (study) for, some with 24-hour access, and lots of knowledgeable people to get advice from. YMMV.

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  • cgosh commented on gwarbeh's instructable Audio Laser4 months ago
    Audio Laser

    Think of it this way.You can send low, bass notes (100 cycles per second, or hz) through your rig. Imagine the headphone or speaker diaphragm (and thus, your eardrum) vibrating back and forth 100 times per second to move the air.You can also send high, treble tones (perhaps 10,000 hz). But video signals (up to 4,000,000 hz -- 4 mHz) must carry far more complicated information, so the frequency used is much, much higher than even the highest treble notes. You've simply exceeded the abilities of your amplifiers.Since the frequency of light waves (the laser) is far higher than video (in the same way that a video signal uses much higher frequencies than audio), your idea might work if you replaced the amplifiers with versions that can deal with video frequencies.You need video amplifiers, b...see more »Think of it this way.You can send low, bass notes (100 cycles per second, or hz) through your rig. Imagine the headphone or speaker diaphragm (and thus, your eardrum) vibrating back and forth 100 times per second to move the air.You can also send high, treble tones (perhaps 10,000 hz). But video signals (up to 4,000,000 hz -- 4 mHz) must carry far more complicated information, so the frequency used is much, much higher than even the highest treble notes. You've simply exceeded the abilities of your amplifiers.Since the frequency of light waves (the laser) is far higher than video (in the same way that a video signal uses much higher frequencies than audio), your idea might work if you replaced the amplifiers with versions that can deal with video frequencies.You need video amplifiers, but you're using audio amplifiers. Any extra light will create video noise (scratchy image) instead of audio noise. You'll use simple bandpass filters to remove that noise.

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  • cgosh commented on Computothought's instructable Foil based fractal antenna.4 months ago
    Foil based fractal antenna.

    Unless I miss my guess, this is why this idea works:Fractals are made up of small pieces that form larger pieces that are multiples of the smallest size.Radio waves do best with a "resonant" antenna length that resonates to match the radio frequency (which is the inverse of the wavelength -- one goes up, the other goes down). This concept is how a good singer can shatter a wine glass, or how you can fill multiple glasses with a little water to play a chromatic scale. Just match the resonant frequency.You can also use 1/2, or 1/4, or 1/8, or double or quadruple the resonant wavelength, or other multiples, with proceedingly lesser impact. Think of the difference between Low C, Middle C and High C on a musical instrument -- they're all just multiples of the same resonance.For exa...see more »Unless I miss my guess, this is why this idea works:Fractals are made up of small pieces that form larger pieces that are multiples of the smallest size.Radio waves do best with a "resonant" antenna length that resonates to match the radio frequency (which is the inverse of the wavelength -- one goes up, the other goes down). This concept is how a good singer can shatter a wine glass, or how you can fill multiple glasses with a little water to play a chromatic scale. Just match the resonant frequency.You can also use 1/2, or 1/4, or 1/8, or double or quadruple the resonant wavelength, or other multiples, with proceedingly lesser impact. Think of the difference between Low C, Middle C and High C on a musical instrument -- they're all just multiples of the same resonance.For example, old Citizens Band [CB] radio antennas were legally limited to a maximum of 20 feet above an existing structure, so they used a 5/8 formula that worked out to just shy of 20 feet. CB car "whip" antennas were 108 inches, which is 9 feet, or 1/4 the 11 meters [36 feet] of wavelength, and 27 mHz in frequency. The actual radio wave is 11 meters, or about 36 feet from top to bottom. Car CB radios use a coil of wire (a loaded coil) in the antenna to make it "electrically" longer. Ham radio operators use multiple coils on a single antenna to make it work well on many frequencies.Making an antenna that is a multiple (or a simple fraction) of the wavelength -- then making up additional patterns that are also multiples -- strengthens the overall ability for the antenna to transfer the weak radio energy in the air into a usable signal.With very high frequencies (television, cellphones, wi-fi) the wavelengths -- and thus the antenna lengths -- get very short. Police radio antennas are just a few inches long now, but they used to be 5 feet or 10 feet long when they were on a lower frequency band (55 mHz or around 6 meters -- a double-length 10-foot antenna flopping around allows a bit more distance from the police station, but it's clumsier).Wi-fi (2.4 gHz, or 2,400 mHz, or 0.125 meters or 125 millimeters) resonant wavelength is 4.92 inches long. But a wi-fi fractal antenna could use lengths of 0.49" (1/8th wave), 0.98" (1/4-wave), 1.96" (1/2-wave), and 4.92" (full-wave) as it's component pieces to achieve a better antenna in a small space. It's like stuffing a bunch of small, resonant antennas inside a big one.Bottom line? Your TV works on many different channels. Pick the one you want the worst (or get the worst signal) and tailor your fractal lengths to match that wavelength, or make multiple antennas and see if you can leave them all connected. YMMV. Use Google to get the numbers you need ('frequency of channel 3' or 'wavelength of 63 mHz').A Yagi antenna does the same thing, but with fewer pieces, and it takes the diameter of the tubing pieces into account (yeah, for antennas, everything matters). If you want to learn more, go to your library's Reference section and look at the ARRL Manual.

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  • cgosh commented on lgrah760's instructable How to find a break in an invisible dog fence5 months ago
    How to find a break in an invisible dog fence

    Your local AM radio stations may or may not be close on the dial to the frequency the dog fence broadcasts. A cheap-o AM radio might work better than an expensive model (less sensitivity and less adjacent-channel rejection on the cheap model). YMMV so try different radios.FWIW, the purpose of a choke is to pass DC current (measured in volts, so the fence system thinks a wire is shorted across the terminals) while blocking any AC (the noisy part that shows up in the radio is NOT shorted out, so it continues down the buried wire). You can make one -- it's just a coil of wire. Google it. Perhaps this system uses a constant DC voltage to test for continuity through the buried wire, and an AC signal (the "noise" you hear) to trigger the dog collar. A break would cause the beep that...see more »Your local AM radio stations may or may not be close on the dial to the frequency the dog fence broadcasts. A cheap-o AM radio might work better than an expensive model (less sensitivity and less adjacent-channel rejection on the cheap model). YMMV so try different radios.FWIW, the purpose of a choke is to pass DC current (measured in volts, so the fence system thinks a wire is shorted across the terminals) while blocking any AC (the noisy part that shows up in the radio is NOT shorted out, so it continues down the buried wire). You can make one -- it's just a coil of wire. Google it. Perhaps this system uses a constant DC voltage to test for continuity through the buried wire, and an AC signal (the "noise" you hear) to trigger the dog collar. A break would cause the beep that tells you the wire is broken (DC missing in the wire loop) and so you fool the system with the choke so you can test with the AM radio. Simply shorting the wire could diminish the signal to the radio, but I'd obviously try it and see if it's loud enough to do the job.

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