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JohanH44

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    • Arduino MKR IoT Carrier As a Game Console
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  • JohanH44 commented on bluebird129's instructable Clothespin Snowflake
    Clothespin Snowflake

    Real snowflakes have six arms, not eight arms. Nevertheless, these are really beautiful. And probably more beautiful than if they had only six arms.

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  • JohanH44 commented on arpruss's instructable Copper Pipe Glockenspiel
    Copper Pipe Glockenspiel

    You can use just any notes for "Twinkle, Twinkle Little Star". Starting at C, it goes C C G G A A G F F E E D D C. Starting at G, it goes G G D D E E D C C B B A A G. Starting at any other note requires a chromatic glockenspiel (the model with a 2nd row corresponding to the black keys of a piano), like A A E E F# F# E D D C# C# B B A.There's no original, "correct" note to start on. It's a French traditional song. I think Mozart wrote his famous variations on the theme in the key of G.

    What a great instructable! I was going to do a similar project. I already bought some "semi hard" chromed copper tube. The semi hard means probably that there are different hardnesses of copper tube. The harder, the better for this project, I assume. And the chrome surface might add some clarity to the sound. After deciding to do the project, I found that there's a contest about creating instruments, which made me start writing an instructable. Then I found this eight years old instructable. I won't re-write an instructable (instead I have some other instrument projects for the contest), but I'll most certainly remake this project and comment. It will be a chromatic glockenspiel. I even had a name for the instrument: celestina. Derived from celesta, because of its heavenly sound.

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  • JohanH44 commented on Essort's instructable Talharpa / Juhikko
    Talharpa / Juhikko

    Thank you for sharing! It's a beautiful instrument. But please check the Finnish spelling. It's called jouhikko.

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  • JohanH44's instructable Wildfire's weekly stats:
    • Wildfire
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  • JohanH44 commented on JohanH44's instructable Wildfire

    Here's an error! There is no binary file in the file list. The last file is not the binary file as I thought, but a temporary file with no use. Don't download it.

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  • JohanH44's instructable Paper Cherokee's weekly stats:
    • Paper Cherokee
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  • JohanH44 commented on JohanH44's instructable Paper Cherokee

    Me too. There's only so much fun in competing in length of flight, when throwing paper gliders. This is something different.

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  • JohanH44 entered Paper Cherokee in the Paper Contest contest
  • I'm about to start a very similar project. I have a vacuum cleaner with a slide for speed control. I haven't checked yet what component the slide is adjusting. If it is a potentiometer, I bet it would be possible to switch to another potentiometer to even go for lower speeds, as long as the motor still runs. The most interesting solution would be to add som PID control, getting input from the organ wind chest (its pressure) and putting the output to the electronic speed control of the vacuum motor.But my first thing to solve is whether I could use cheap hobby servos instead of solenoids. The reed organ I will rebuild needs very little pressure on the key, maybe 0.3 N while movement is some 20 mm. Roughly calculating a hobby servo might have specs like 3 kgcm, that is 30 N on 10 mm. And th…

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    I'm about to start a very similar project. I have a vacuum cleaner with a slide for speed control. I haven't checked yet what component the slide is adjusting. If it is a potentiometer, I bet it would be possible to switch to another potentiometer to even go for lower speeds, as long as the motor still runs. The most interesting solution would be to add som PID control, getting input from the organ wind chest (its pressure) and putting the output to the electronic speed control of the vacuum motor.But my first thing to solve is whether I could use cheap hobby servos instead of solenoids. The reed organ I will rebuild needs very little pressure on the key, maybe 0.3 N while movement is some 20 mm. Roughly calculating a hobby servo might have specs like 3 kgcm, that is 30 N on 10 mm. And the speed is some 0.2 s on 60 degrees. With a servo horn of 20 mm turning 60 degrees I get a movement of 20 mm. With a horn of 20 mm I lose half of the force, so I have about 15 N. Now I could make the movement faster by turning only 30 degrees and doubling the horn length. That leaves me at 7.5 N. If the speed is not enough, I still have a way to go when the required force is only 0.3 N.Bottom line is that a hobby servo seems to be a considerable alternative to a solenoid. Is it? Have I missed something? The hobby servos might not be as reliable in the long run. Lots of cogs spinning during the flight of the bumble bee.

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  • The sensor reads the amount of infra red light. Nothing more. The rest is in the code. You might have a lot of infra red light around you. I tested the sensor while the lights were on in my room. The lights flicker with 50 Hz (Finland). This I could see in the output from the sensor. So to get a good reading from the sensor, I calculated the average of all readings during a 20 ms period. Plotting a curve of the averages I got, created a nice graph showing how my blood vessels in my finger tips pulsed with my heartbeats. If there are other significant infra red noise sources, you might need to smoothen the graph further. After that it's about recognising rising slopes or peaks or whatever looks easiest to get the rate. Some count beats in a 15 s period and multiply it with 4 to get the BPM…

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    The sensor reads the amount of infra red light. Nothing more. The rest is in the code. You might have a lot of infra red light around you. I tested the sensor while the lights were on in my room. The lights flicker with 50 Hz (Finland). This I could see in the output from the sensor. So to get a good reading from the sensor, I calculated the average of all readings during a 20 ms period. Plotting a curve of the averages I got, created a nice graph showing how my blood vessels in my finger tips pulsed with my heartbeats. If there are other significant infra red noise sources, you might need to smoothen the graph further. After that it's about recognising rising slopes or peaks or whatever looks easiest to get the rate. Some count beats in a 15 s period and multiply it with 4 to get the BPM. I simply measured the milliseconds between each beat and averaged the resulting BPM with two or three previous ones.So the sensor doesn't give you a BPM value. It only gives a value telling how much IR the photo transistor receives.

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  • Great idea, especially being analog. Nevertheless, my suggestion for development would be replacing the spinning motor with static coils. The coils (several) would be controlled by a microcontroller. The tip of the top would be a pen. Varying the current strength in the coils will control the position of the spinning top, which will draw something, say tarot symbols at a spiritistic seance.

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  • JohanH44 commented on lingib's instructable CNC Dual Arm Plotter

    My servo is a Turnigy TGY90S Metal Gear Servo 1.8kg / 13.4g / 0.10sec. I just happened to find them in a 2nd hand market, so they were by no means hand picked for this project. I guess the stepper motor approach is way better. I picked the 1:1 ratio for simplicity, too. But then I realised that the maths are not that harder for any ratio! A² = B² + C² - 2BCcos(a) where A is the elbow-pen-arm and a its opposite angle you want to find.I have yet to "calibrate" my servos. They don't turn a full 180 degrees, though my code expects them to do so. But my tests show that the servos (with minimal load) rotate each time very precise to same position for any given angle.To minimise friction at the elbow joints, I've thought of using flat bearings. And neodym magnets 1 mm fr…

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    My servo is a Turnigy TGY90S Metal Gear Servo 1.8kg / 13.4g / 0.10sec. I just happened to find them in a 2nd hand market, so they were by no means hand picked for this project. I guess the stepper motor approach is way better. I picked the 1:1 ratio for simplicity, too. But then I realised that the maths are not that harder for any ratio! A² = B² + C² - 2BCcos(a) where A is the elbow-pen-arm and a its opposite angle you want to find.I have yet to "calibrate" my servos. They don't turn a full 180 degrees, though my code expects them to do so. But my tests show that the servos (with minimal load) rotate each time very precise to same position for any given angle.To minimise friction at the elbow joints, I've thought of using flat bearings. And neodym magnets 1 mm from each other to keep the joints together. No bolts! No contact point other than the bearing balls. This I'll let wait until I get hands on a 3D printer. With the printer I will create 1:2 or even 1:3 arms with perfectly fits for the servo horns, the bearing beds, the magnets etc.

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