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c.r.h.

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  • c.r.h. commented on rabbitcreek's instructable Giant Analog CO2 Meter
    Giant Analog CO2 Meter

    While its good to know that you understand some of the CO2 cycle, but what would you like your students to learn about our environment? Watching CO2 levels can be very interesting. This project can make for a great learning tool.

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  • c.r.h. commented on rabbitcreek's instructable Giant Analog CO2 Meter
    Giant Analog CO2 Meter

    Very Good! I use the K30 from CO2meter and a Raspberry Pi to log outdoor CO2 levels among other things. If you live near an area with any industry you might be surprised with how your CO2 levels vary throughout the day and night. For us, it's not unusual for outdoor CO2 levels to rise overnight and remain high throughout the morning. It seems to be a very effective measurement for determining the presence of a surface inversion that can trap industrial emissions close to the ground. Particulate (PM2.5) and VOCs may ramp up as well when air currents carry the emissions our way.

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  • Solderless Electrical Connector

    I keep a box of assorted Wago 222 series lever-nuts on hand. Insulated and reusable. They're available at Amazon.

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  • c.r.h. commented on 陳亮's instructable Arduino Watch Core
    Arduino Watch Core

    Looks like it would make a really great desk clock too.

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  • DIY Weber Grill Cart BBQ Station

    Nice Idea but any safety concerns? Wood in direct contact with the Weber. Maybe create an air gap between the grill and the table top and suspend the grill in a fire safe way.

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  • Zero clearance insert (Ridgid table saw)

    A word of Warning. A metal insert will through metal chips upon the initial cut through it but may also periodically throw metal chips if the arbor has even just a small amount of play in it. I just made an aluminum insert and I'm a little conserned about the safety aspect.

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  • Simple Arduino Home Energy Meter

    Since the output of the current transformer is AC, doesn't the output (after the shunt resistor) need to be rectified and smoothed. No need to bias such a circuit so long as the common of the rectified signal is common the the Arduino's analog ground. Hardware signal scaling would be accomplished via the shunt resistor value.

    Hum...If using min and max values, how about instead of subtracting 516 counts as an offset, consider:RMScurrent = (maxCurrent - minCurrent)/2.0 *0.707 / (your constant)

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  • DIY 300 to 75 Ohm TV Antenna Coaxial Baluns

    Was Googling around for baluns and found your Instructable. You may want to double check the transformer schematic. On the 300 ohm side where the two windings #2 & #3 connect, I think that net should float, not connect back to the 75 ohm ground. As it is shown currently, winding #2 is shorted.

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  • c.r.h. commented on othermachine's instructable The Nerd Watch
    The Nerd Watch

    Neat Project. For the watch strap... There are some one piece nylon watch straps out there. I found a few on Amazon but they are 18-22mm wide typically. Could modify PCB for a std. one piece strap for a highly finished look. Just need to weave the strap through the two slots in the PCB.

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