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Community Feedback 03 - Power Safety Concerns!

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element14's The Ben Heck Show

Join the Ben Heck team every week for amazing hacks! Watch them build and mod community-inspired projects using electronics!

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Community Feedback
Super Glue Gun
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Ben and Karen look through suggestions from anywhere on the element14 community on a segment called Community Feedback. This segment focuses on the Super Glue Gun Build after it just got started. Suggestions include putting a "do not try this at home" warning label when attempting to hook up mains to a breadboard in front of an audience, discussing different loads with their glue gun, and an excel sheet to deal with the non-linearity of thermistors.

 

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  was concerned when the team attempted to hook mains up to a breadboard. Ben’s explanation is that he does not consider 120 volts to be that dangerous, when they did the test they made sure that everything was isolated, and that this was the fastest way to hook it up.  Karen parses Ben’s explanation by letting the audience know that while it isn’t the safest method, it’s the fastest method, so don’t try this at home.

 

  suggests that the team talks about different types of loads with their Super Glue Gun.  The glue gun heater coils have low inductance and are mostly resistive. As they get hotter, their resistance changes. So measuring the cold resistance is not the same as the resistance when it is hot. As Ben explains to Karen, we can’t necessarily know what the current draw actually is. It probably won’t make a difference, since they’re using AC, but if the triac is rated lower than what they need, and they are actually drawing more current than they think they’re going to use, then they could blow out the triac. The real problem with electricity is when electricity has no stopping point.

 

In his designs, typically uses 25C NTC thermistors as ambient sensors for oven controllers, while he uses a K thermocouple for the thermal enclosure. He was struck by the non-linearity of the thermistors so he made a spreadsheet, which he offers the team, to help calculate correction factors for Arduino controllers converting the ADC value to a calculated ambient temp.

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  • I'm appalled by how you approached the AC current. 120V DC is probably okay to touch, a little tingly and uncomfortable, but the Alternating wave of AC makes a prime source to turn the human body into a nasty capacitor. If you touch it intermittently, you might be okay, but if you hold on, you'll turn yourself into a charge pump, and with every second the damage will be worse and worse.

     

    This is not a good attitude to have around mains power. Mains power kills. Don't be so sure your breaker is going to throw, because in a house like mine, as old as it is, it isn't grounded properly. A GFCI wouldn't detect the overload until too late, and the breaker will have thrown long past my expiration.

     

    Stay safe everybody. Be very, very, extremely careful around AC. If you aren't sure, don't go near it.

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  • I'm appalled by how you approached the AC current. 120V DC is probably okay to touch, a little tingly and uncomfortable, but the Alternating wave of AC makes a prime source to turn the human body into a nasty capacitor. If you touch it intermittently, you might be okay, but if you hold on, you'll turn yourself into a charge pump, and with every second the damage will be worse and worse.

     

    This is not a good attitude to have around mains power. Mains power kills. Don't be so sure your breaker is going to throw, because in a house like mine, as old as it is, it isn't grounded properly. A GFCI wouldn't detect the overload until too late, and the breaker will have thrown long past my expiration.

     

    Stay safe everybody. Be very, very, extremely careful around AC. If you aren't sure, don't go near it.

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