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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    The inductance change from introducing a metal can go in two directions: electrical conduction lowers the inductance, ferromagnetism increases the inductance. Pure iron does both, and depending on the type of iron and is geometry, either of two mechanisms will dominate. I guess scanning over a range of frequencies might give a better distinction, but that'd be a project by itself!

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  • rgco commented on rgco's instructable LEGO Quartz Clock
    LEGO Quartz Clock

    Glad it worked, sorry I didn't reply in time since I didn't understand the question!

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    You can try but you'll need to increase the number of pulses, so it will get slower. Contrary to many other circuits, the value of the capacitor matters here!

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  • Strong and Stable Magnetic Levitation

    It all depends on the magnet, the coil and the current. In my case ~50 grams. To get more levitating power, the electromagnet can be 'helped' by a permanent magnet, such that the permanent magnet provides the bulk of the levitating power and the electromagnet is only used for stabilization. I think that's what's being done in the commercial 'push' levitation devices. But it's dangerous for the 'pull' configuration since the permanent magnets are oriented to attract so they will slam into each other when the device goes out of equilibrium.

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  • rgco's instructable Arduino Timers: 8 Projects's weekly stats:
    • Arduino Timers: 8 Projects
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      0 comments
  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    It should. The choice of pins is free, and there is no hidden direct port access, so a single change of the pin definitions a the beginning of the code is sufficient. The only constraint is that pin_cap is an analog pin.

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    Hi, in Arduino analog pins can also be used as digital pins, and indeed even as digital output (except for A6 and A7 on the Nano, which are analog input only). I don't know about STM32. However, if the pins have a fixed function, I think it should not be a problem to connect the capacitor to both and analog input and a digital output pin

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    That'd be a crown for the queen!No, this type of metal detector won't reach that kind of sensitivity over a large volume, anything smaller than ~1/10 of the coil size can't be detected. There may be other electromagnetic methods based on a device with a certain resonance frequency (similar to RFID tags) but that's beyond my skills!

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    No a capacitor doesn't discharge by itself on these timescales (they can hold charge for days). Increasing both L and C (within reasonable amounts) should give the same result without need for code change

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    Yes, up to 6 coils would be relatively straightforward, I think, since The arduino has six analog inputs

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  • rgco entered LEGO Quartz Clock in the Clocks Contest contest
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  • rgco commented on rgco's instructable Arduino Waveform Generator
    Arduino Waveform Generator

    Sorry, I have no idea, I never did anything with I2C. I agree the present LCD display has an annoyingly large number of wires to solder, but it works quite robustly!

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    Yes, the relative change in inductance is proportional to the relative size of the coin to the coil. So a smaller coil will be more sensitive to smaller coins. Try half the size. To keep the overall inductance the same, double the number of coils.

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    Ah, you mean the cross-sectional area of the wire? it is not critical, as long as the total resistance of the coil stays well below the value of the external resisitor (220Ohm here). Indeed I saw no difference between thick hookup wire (0.5mm diameter) and thin cheap discarded wire (in the 0.2-0.3mm range)

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    looks like you are spot on. minval and maxval are the extremes of the adc readings, so you are between 200 and 300.

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    I think it should work. Make sure the area between the two wires is small, so use either coaxial cable or twisted pair, or just make sure that the two strands are close and twist them yourself a few times. It may also help to increase the value of both L and C, so that you're less sensitive to stray capacitance/inductance. e.g. 40 turns instead of 18 and a 47nF capacitor. Good luck!

    In theory yes: a higher L will give longer pulses, so the capacitor will charge up quicker. You cn compensate for that by having a larger value for C. In principle it should scale. So 100 windings has 25x the inductance of 20 windings, so the capacitor should be 25x larger too, 250nF instead of 10nF. Try 220nF or 33nF. Good luck!

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    Nano. yes it seems small, but it needs to charge up from tiny current spikes...

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    I'm glad you like it! it's more than 3 years ago that I posted this!

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  • rgco commented on rgco's instructable Arduino Waveform Generator
    Arduino Waveform Generator

    Very strange! the cursor should move to the first letter of the waveform if you keep turning left with the button pushed. Then turning without pushing changes the waveform. From your description it doesn't seem to be a hardware problem, but if you dowloaded the code it can't be a software problem either!

    Very strange! the cursor should move to the first letter of the waveform if you keep turning left with the button pushed. Then turning without pushing changes the waveform. From your description it doesn't seem to be a hardware problem, but if you dowloaded the code it can't be a software problem either!

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  • rgco commented on rgco's instructable Animated Heart
    Animated Heart

    Thanks! Actually not really easy, I messed up the wiring twice before getting it right, but to my defence, I was a bit in a hurry, it was Feb 13 :-)

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  • rgco's instructable Paper Molecular Models's weekly stats:
    • Paper Molecular Models
      94 views
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      6 comments
  • rgco commented on rgco's instructable Paper Molecular Models
    Paper Molecular Models

    Thanks! Actually the 'trigonal' shapes also works for the trigonal bipyramidal geometry, I updated the text. Square planar might be doable too, but octahedral is harder (it is not a tube, the 6-fold and 4-fold symmetries interfere...

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  • rgco commented on rgco's instructable Portable Magnetometer
    Portable Magnetometer

    Well spotted, now corrected. Thanks!

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  • rgco commented on rgco's instructable Paper Molecular Models
    Paper Molecular Models

    I tried to! I've been having lots of hiccups with the website recently...

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  • rgco's instructable Animated Heart's weekly stats:
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  • rgco's entry Portable Magnetometer is a winner in the Magnets Challenge contest
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  • High-speed Clock for Slow-motion Videos

    Nice, thanks for sharing!

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  • rgco's instructable Light Up a Toy Greenhouse's weekly stats:
    • Light Up a Toy Greenhouse
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  • rgco commented on rgco's instructable Portable Magnetometer
    Portable Magnetometer

    I'm afraid not. This probe is for strong magnetic fields, in the 0.1-100mT range. The earth magnetic field is of order 0.1mT, so you'd want a probe with a _much_ higher sensitivity. I have no experience with those, but I'm pretty sure they exist!

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  • rgco commented on rgco's instructable Induction Demonstrator
    Induction Demonstrator

    The copper tube demo is all over youtube and facebook. But nothing beats hand's on. The coils are a little harder to make but it's more original. The other tube is aluminium. It has a slightly higher resistivity, so for equal dimensions it slows down the magnet less.

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  • Toothbrushtimer With the ATtiny13

    The 18650 gives 3.7V. That's fine for the ATTINY and for the LEDs, but the datasheet of the MAX7219 says 4.0-5.5V. It might work in practice, but probably it will give up in a strange way somewhere halfway the battery life. Note that this is an extremely power-saving design, and there should be no need for the super-powered 18650 batteries. It's been running for 2y straight without ever changing batteries and without ever switching it off. The sleep mode is extremely efficient. I have some recovered 18650's but I avoid them when possible, I've seen too many videos of them going up in flames...

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  • rgco commented on rgco's instructable Portable Magnetometer
    Portable Magnetometer

    Great! Let me know if something is not clear!

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  • rgco commented on rgco's instructable Portable Magnetometer
    Portable Magnetometer

    Haha, I had to lookup what a pinpointer is!! I found an instructable here: https://www.instructables.com/Pin-Pointer-Metal-Detector-Arduino/. Bad news: this magnetometer can't be used as a pinpointer: it is meant to measure existing magnetic fields, while a metal detector creates magnetic fields (at high frequencies) and looks for the reaction of metal objects to that field.Metal detectors usually use coils to detect magnetic fields. At high frequencies, that's much more sensitive than Hall sensors, which instead are better at low frequencies, and can measure static fields, which is not possible with a coil.

    The author, https://www.instructables.com/member/TechKiwiGadgets/instructables/has three instructables of metal detectors, I think they all work on the same principle. Beware I once ordered "LM339 Quad Voltage Comparator" from Aliexpress and received fakes!I also once made an instructable of a metal detector https://www.instructables.com/Simple-Arduino-Metal-Detector/ that is incredibly easy to make (just an Arduino, a coil, a resistor, a capacitor and a diode), and maybe could be turned into a pinpointer by making a small coil.

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  • Strong and Stable Magnetic Levitation

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bu…

    see more »

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bunch of capacitors (1muF, 100muF, 2200muF in parallel) it would not be stable! I interpreted this as coming from a coupling of mechanical oscillations into the electrical circuit: the voltage of the buck converter dips a bit when there is large current draw, and that changes the output of the Hall sensor, possibly resulting in a positive feedback. It got somewhat better when I took the power to the Hall sensor directly from the buck converter output, but it was a lot better with a separate regulator.

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bu…

    see more »

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bunch of capacitors (1muF, 100muF, 2200muF in parallel) it would not be stable! I interpreted this as coming from a coupling of mechanical oscillations into the electrical circuit: the voltage of the buck converter dips a bit when there is large current draw, and that changes the output of the Hall sensor, possibly resulting in a positive feedback. It got somewhat better when I took the power to the Hall sensor directly from the buck converter output, but it was a lot better with a separate regulator.

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bu…

    see more »

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bunch of capacitors (1muF, 100muF, 2200muF in parallel) it would not be stable! I interpreted this as coming from a coupling of mechanical oscillations into the electrical circuit: the voltage of the buck converter dips a bit when there is large current draw, and that changes the output of the Hall sensor, possibly resulting in a positive feedback. It got somewhat better when I took the power to the Hall sensor directly from the buck converter output, but it was a lot better with a separate regulator.

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bu…

    see more »

    Hi, thanks for your feedback!Concerning stability: The 'stable' in the title refers to the mechanical stability: when the suspended magnet wiggles, its oscillations tend to damp out (slowly). The electrical part is indeed astable, but at a very different frequency. My limited understanding is the following: there is a double feedback loop: fast electrical feedback from the electromagnet and slow mechanical feedback from the suspended permanent magnet. The resulting oscillation frequencies differ by 3 orders of magnitude and don't interfere. It'd be interesting to analise and/or simulate for engineering students (as MIT did 16years ago!)Concerning the LM7805: I first did what you suggest: run the electronics from the same 5V as the magnet, but the thing was shaking like mad! Even with a bunch of capacitors (1muF, 100muF, 2200muF in parallel) it would not be stable! I interpreted this as coming from a coupling of mechanical oscillations into the electrical circuit: the voltage of the buck converter dips a bit when there is large current draw, and that changes the output of the Hall sensor, possibly resulting in a positive feedback. It got somewhat better when I took the power to the Hall sensor directly from the buck converter output, but it was a lot better with a separate regulator.

    View Instructable »
  • rgco's entry Induction Demonstrator is a winner in the STEM Contest contest
    • Strong and Stable Magnetic Levitation
      1,669 views
      23 favorites
      1 comments
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  • rgco commented on rgco's instructable Portable Magnetometer
    Portable Magnetometer

    hi, thanks. You mention a 'mic'. Do you mean microphone, to pick up audio? That's a different subject! Anyway, to detect a certain frequency from an analog signal, the Fourier transform is the standard tool. I've never coded that but I'm pretty sure there are example codes and maybe even libraries around for the FFT (Fast Fourier Transform). Good luck!

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  • Reuse an Old Phone and Old Speakers As a STEREO

    Hi. The 220Ohm resistors simulate the impedance of headphones. Without them, one of my phones would not recognise the presence of headphones and would continue to make sound over the main speaker. They also increase the current flow which reduces pickup noise (not 100% sure about this).The potentiometer works as a voltage divider, so yes it should be connected to ground on one side. Without that it wouldn't be effective for volume control I think.

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    I'm not sure I understand. 0V, negative and ground are the same in this case.

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  • Electromagnetic Levitation Device

    Hi, I came to exactly the same conclusion: I can just get it to work, but only for a very small magnet. Basically, my 3144 hall-switch is too sensitive. I say 'my' because the datasheet specifies 70-350Gauss for the operating point, so there may be a very large variation between individual parts. The magnet has to stay far from the sensor, but close to the coil, meaning that the sensor ends up in the center of the coil. But then at high current the coil itself switches off the sensor. Too bad I really like the simple schematic. If there were a way to reduce the sensitivity of the sensor, it could work great, but the only way out I see is indeed the linear hall sensor.

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  • rgco commented on rgco's instructable Arduino Waveform Generator
    Arduino Waveform Generator

    Looks like a problem with uploading. I guess you choose for Board "Arduino Nano", the check Processor, there is "ATmega328P" and "ATmega328P (old bootloader)". I need to choose the latter to upload succesfully

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  • rgco commented on rgco's instructable Magnetic Circuit Blocks
    Magnetic Circuit Blocks

    Thanks for the compliment! I think these circuit blocks compare favourably to the scrappy circuits. I'm now using the blocks for actual prototyping. Yesterday I added the Joule thief as step 10 to the description. It's a high-frequency circuit (~100kHz) and there are no problems with stray capacitance or stray inductance. In minutes I could make and evaluate several variations of the circuit (LEDs in series, vary the base resistor, add resistance to the battery etc)

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  • rgco's instructable Magnetic Circuit Blocks's weekly stats:
    • Magnetic Circuit Blocks
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  • rgco commented on rgco's instructable Magnetic Circuit Blocks
    Magnetic Circuit Blocks

    Thanks! Indeed, contrary to the commercial sets, if you miss a crucial component for an interesting circuit it's made in 2 minutes. And the quality is just as good if not better. If I find a 5mm think 25mm wide wooden beam, I might try a wooden version as well.

    Thanks! Indeed, contrary to the commercial sets, if you miss a crucial component for an interesting circuit it's made in 2 minutes. And the quality is just as good if not better. If I find a 5mm think 25mm wide wooden beam, I might try a wooden version as well.

    Thanks! Indeed, contrary to the commercial sets, if you miss a crucial component for an interesting circuit it's made in 2 minutes. And the quality is just as good if not better. If I find a 5mm think 25mm wide wooden beam, I might try a wooden version as well.

    Thanks! Indeed, contrary to the commercial sets, if you miss a crucial component for an interesting circuit it's made in 2 minutes. And the quality is just as good if not better. If I find a 5mm think 25mm wide wooden beam, I might try a wooden version as well.

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  • rgco commented on rgco's instructable Simple Arduino Metal Detector
    Simple Arduino Metal Detector

    I am glad you like it and plan to use it in class! There is plenty of room for improvement, and the code should be rewritten from scratch.

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  • rgco commented on rgco's instructable Magnetic Circuit Blocks
    Magnetic Circuit Blocks

    Thanks! I couldn't agree more!

    Interesting idea! I didn't know it existed, how does that work? or do you have a link? I'd be happy to add that suggestion to the text. It may end up less sturdy though, the soldering does help to keep the component in place

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  • rgco commented on rgco's instructable Arduino Waveform Generator
    Arduino Waveform Generator

    4Hz is no problem. It goes down to 1mHz

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