April 29

Some Stupid Rules

Maturity is knowing you were an idiot in the past.
Wisdom is knowing you will be an idiot in the future.
Common sense is knowing you should try not to be an idiot now.

We as a community (the internet) are becoming increasingly concerned with pointing out how something could go wrong, or the safety concerns of any project.  Whether the reason is an increasingly litigious society, a greater average degree of inexperience working with tools and materials, or other factors, any write-ups, instructions, or videos explaining how to create are invariably littered with commenter (if not the author) helpfully pointing out how they should be safe and not put an eye out.The fact is that everything we do, including doing nothing, carries a moment-by-moment risk of harming or killing ourselves.  This in mind, The Stupid Rules – the basic and overarching guidelines you need are:

  • Don’t be stupid doing projects: Don’t show off, don’t rush, don’t work drunk or high or sleep-deprived or impaired.
  • Don’t be stupid with new tools: When using a new tool, learn what it is and what precautions to take.  Get instruction, find a video, take it slow and focused the first few times, and initially follow the instructions and advice on how to use it.
  • Don’t be stupid with new materials and systems: Cutting MDF for the first time? Spray-painting? Wiring a breaker?  Stop and learn about what you are working with.  Get advice, find an instructional sheet or video, and follow the advice, precautions, and instructions on handling.
  • Don’t be stupid with familiar tools and materials: Working with 14 molar HCl all the time does not make it any less dangerous if you do something stupid with it.  Understand what precautions you are taking and why before you decide to violate them.

Bonus guidelines, once you have a handle on the cardinal Stupid Rules:


  • Don’t be stupid around other people’s projects (aka a hacked, modded, rough, or even final thing or system):  It may look cool.  It may look safe.  It is shiny and you want to touch it, play with it.  ASK FIRST.  It may be dangerous if mishandled, it may be delicate; it is always courteous.
  • Don’t be a whiny butt if you do something stupid: If you get hurt or something gets screwed up, learn why and fix it if you can.  Don’t whine and moan and sue some random manufacturer because they thought “don’t dry-hump our product” was a obvious enough that it did not warrant a printed warning.
February 4

Class X/Class Y (Safety) Capacitor Parameters

“There are more capacitors in a distributor catalog, Horatio, than are dreamt of in your philosophy. “ – Shakespeare  (I think? Close enough)

Safety caps-Appliance Class ISpecifically, I am talking about Safety capacitors, aka X-capacitors, Y-capacitors, XY-capacitors, RFI/EMI suppression capacitors, line filtering capacitors, and no doubt other modes of reference.

When you have the occasion to mix hazardous household voltage with capacitors (perhaps to keep noise from leaking out of your circuit, or for surge protection), special care needs to be taken in selecting the capacitors used.

Normal ceramic capacitors have the distressing tenancy of failing short.  In the case of diagram to the right, such a capacitor in the “Cx” position would cause the mains to short through the capacitor, creating a risk of fire, (small) explosion, and a Bad Day.  Should the failing capacitor be in the “Cy” position, the mains could be shorted to earth ground (risking fire, etc) or, if the case is not connected to earth, could just directly connect the case to mains, creating the risk of arcing, electrocution, and a Bad (hair?) Day for someone. Continue reading