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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.

  • Here is a schematic of something pretty simple that I used this tool on

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    More information about the Selector FPGA is available in he document section of the site http://www.bifrost-group.com

    J.R.

  • I would still like to share my thermistor tool with you as I think others might want to use it for their designs.  I use it for helping me with PID controller circuits albeit the primary feedback comes from a cold-junction compensated thermocouple circuit instead of the NTC thermistor.  That one is used to measure ambient air temp near the logic and PWM drive a 12V cooling fan inside the enclosures.  BTW I am a size 3XL-kinda guy. image  Here is a link to the file:

     

    https://storage.googleapis.com/wzukusers/user-13694351/documents/560ee5ef8a0d3R8ed9pD/epcos%20thermistor%20resistance%20table.xls

  • I've been enjoying the Ben Heck Show Videos for some time, but the tone of this one seemed so peculiar to me that I felt it merited comment.

     

    The video, overall, seemed somewhat... dismissive? That may not be the correct word, but I got the impression that the comments which were discussed in the video were not considered welcome or interesting. Safety concerns are sadly brushed aside more than once, with an accompanying hint of sarcasm, and the comments about the inductive load and the spreadsheet also seemed to elicit little interest from either presenter. Unless I miss my guess, there was even an element of mockery directed towards mr_widget's choice of words in his comment.

     

    Obviously this is all speculation and my personal interpretation of vocal intonation and body language, so it is highly susceptible to bias on my part, but at the very least, I think that if the presenters do not have some enthusiasm for discussing and addressing the comments at hand, then one either needs to defer filming until more interesting comments are available, or the hosts are more interested in the discussion.

     

    You folks do amazing work, and I'm sure your occupations place great demands on your time and energy, I just hope that if these community feedback segments continue, the people filming them will find more satisfaction in doing so.

     

    As regards safety, by way of example, many people who record themselves handling firearms take great pains to visibly and consistently demonstrate safe handling beyond what is strictly necessary in a controlled environment. This enhances their personal safety, but also emphasizes safety culture to the viewer. It may determined that it is neither practical nor important for the Ben Heck Show to do the same, but the cost vs benefit of promoting public safety through enhanced personal safety is worth consideration.

  • Hi TBHS! Thanks for featuring my comment.

     

    That comment, especially the other one on youtube, kinda blew up with all sorts of ranting. I didn't mean for that to happen.

     

    Sure, I totally agree that 120V isn't THAT dangerous. As long as you know what you are doing. I have never touched it personally, I am sure if I did I would be totally fine. I know people who have touched it and are fine. But I also know someone who has touched it and now two children grow up without a father. That happened recently. So that is kind of the reason for my strong position.

     

    Really, my desire to see a warning label on thing like this is geared more towards a large demographic of yours that I frequently see replicating your projects. I have lots of friends and children of friends who are young engineering/late high school students who are motivated and enthusiastic soon-to-be engineers. You motivate them with your fun and exciting projects and more than once I have been asked for help in trying to build something you have built.

     

    I believe everyone I know is smart enough to know the dangers of mains. But they don't necessarily know all good practices and when you are standing around a desk for hours building and debugging, accidents happen. Death by electrocution isn't even really the main concern. How long does that thing take to heat up? Probably enough time to go and make a coffee? A lot can happen in a couple of minutes around an unattended desk. Breadboards may handle mains just fine in normal circumstances. But your $2 Ebay breadboard will be a ball of molten flaming plastic in a matter of seconds at the first sign of a short.

     

    But hey, it is your content, your show. Realistically, nobody is going to get hurt trying to copy you so it is not your responsibility to pander to the lowest 1%.

    I enjoy all of your episodes.

    Warning label or not. Just keep doing what you are doing and I will keep watching.

  • 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.

  • Dear Mr Heckendorn, et. al,

    I have just watched your video on Power Safety Concerns and am appalled by your cavalier attitude towards the dangers of electrical shock.

    Speaking as a UK Chartered Electrical Engineer who has witnesses first hand the life changing impact an electrical shock can have it simply amazes me the level of incompetent stupidity in your statement not considering 120VAC 'to be that dangerous'.

    Why not take some of your own advice and use the oft' well published Element14 community where you can connect and collaborate with...

    Perhaps if you had you would not be so quick to make dangerous asinine comments.

     

    I can't believe Farnell condone this type of clap trap.