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  1. jimkirk

    smallest solar cell

    As Keith said, LEDs (non-phosphor color converted like white) work as micro solar cells, generally most sensitive to their emission color. https://www.youtube.com/watch?v=6WGKz2sUa0w Traditional solar cells... I easily found 17 mm diameter and 22 x 7 mm cells...
  2. jimkirk

    Current Question

    I ran a length of a couple hundred LEDs like this. Used a pair of 10 AWG wires for power and ground and tapped the individual strings off that, with the data lines all in series for control. Worked fine.
  3. jimkirk

    "Off-the-Shelf" NEMA 17 or 23 Stepper Motors Rated for -40°C?

    Maybe https://www.linengineering.com/products/stepper-motors/specialty-motors/high-low-temperature-operation-motors?gclid=CjwKCAiAvriMBhAuEiwA8Cs5leuCFuS0Uk2gmutVqyI0hH9yeDmBbxkRAqKUM6nZ40VFfmtBpmoiIRoCa14QAvD_BwE
  4. jimkirk

    MOSFET or similar devices that hold their state when unpowered.

    For how long does the state need to be retained? I'd guess a simple CMOS flipflop driving a non-protected gate MOSFET powered by a lithium coin cell could maintain its state for years.
  5. jimkirk

    MOSFET or similar devices that hold their state when unpowered.

    There was a company that used a technique they called "Mechanically Orbited Carbon" to make analog RAM that was completely passive, random access, and non-volatile. Here's the manual, it's a hoot. https://www.makenoisemusic.com/content/manuals/analogmemorymanual.pdf
  6. jimkirk

    Semiconductor handbooks and book of circuits

    The G.E.Transistor Manual. I still have my old copy. Good stuff. Even has a section on tunneling diodes. Here's a link with a few for under $10. Cool...
  7. jimkirk

    Battery pack for robot

    Also, if you're scratch building them, how are you sourcing your cells? If you aren't getting known new, guaranteed in spec cells, you'll want to evaluate them for capacity, internal resistance, & leakage, and then sort them to get roughly the same characteristics per parallel block of cells...
  8. jimkirk

    Battery pack for robot

    These folks have an interesting non-welding battery construction kit. Also Battery Management boards, cells, and related stuff... https://vruzend.com
  9. jimkirk

    Battery pack for robot

    Six in parallel, then put those parallel sections in series. Be sure to match cell voltages before connecting them in parallel. (You can put them in parallel with each one having a low value resistor (1 ohm or so)and letting the voltages equalize for a while. When the voltages are within a few...
  10. jimkirk

    Battery rating and use...can I substitute..?

    The charger will be putting out a constant current for most of the charge, no danger there at all. In fact it will be a gentler charge for the battery, so that's good (assuming it's from a reputable manufacturer.) Some chargers have a time out function as an added safeguard, so going to a much...
  11. jimkirk

    Tunable Luminaires for full Circadian Rhythms

    I've use some of their products. Good stuff. https://www.yujiintl.com/tunable-spectrum.html
  12. jimkirk

    Noisy Neopixels

    How critical is the optical timing? I'd forget the Y connection, just make your string 12 neopixels long and duplicate the pattern in the driving software.
  13. jimkirk

    Replacement triac for T1613MH

    https://www.mouser.com/ProductDetail/Littelfuse/Q6015R5?qs=%2Fha2pyFaduj3hnNIuSp8lkJkUXFVZjpZ2dt8cxhBt6U%3D
  14. jimkirk

    Class induction demonstration toy.

    Here's another fun demo video you can easily replicate. https://www.youtube.com/watch?v=J9b0J29OzAU
  15. jimkirk

    Capacitor only filter for a twitter

    If the issue is that the woofer is "dominating the sound", a simple solution might be to add a resistor (an ohm to ten ohms or so) in series with the woofer to reduce the bass. Be sure to use one with a suitable power rating.
  16. jimkirk

    PCB coil to replace hand wound coil for inductive charging

    Your photo of the original coil looks like it's made of Litz wire, hundreds of separately insulated conductors in parallel to mitigate skin effect at high frequencies, so Q may very well be a factor.
  17. jimkirk

    ADC lag at specific values

    What op amp are you using? This could be zero-crossing distortion (but not around zero if your power supply isn't bipolar). It would typically be somewhere around half the supply voltage (but could be anywhere between 25 ~ 75% or so). Each unit would be a bit different, may drift with...
  18. jimkirk

    Integrate ampere measurement over time?

    You'll have to provide a power supply for it (it draws very little current, 100 uA or so, 1.5 uA in shutdown). Since you've got a battery, you could probably power it by 2 or 3 cells closest to ground with no ill effect and put the shunt in series with that and the more positive cells...
  19. jimkirk

    Integrate ampere measurement over time?

    Not I2C, but this might be of interest: http://www.linear.com/product/LTC4150 Generates a level to tell the direction of the current and a pulse with the frequency proportional to magnitude, it does the integration for you. Designed as a coulomb counter for battery management, has pretty good...
  20. jimkirk

    Best technique for supplying different voltages from one battery source

    One point I don't see mentioned, if you really do need to generate 13 volts from your LiPO... Your nominal 14.8 volt battery sounds like it has 4 cells. The typical cell voltage for common lithium batteries is 3.7 volts, times four gives 14.8. A fully charge cell is usually 4.2 volts (there...

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