videos and diagrams
Personal Pollution Protection in China and Everywhere
For USD $3.49 + tax I got a 3M 8211 flap valve respirator similar to this one at
but when I'm exerting myself it's an effort to suck enough air through
the small face mask. I also want to show I'm not contagious, I'm
blocking bad air, especially the awful toxic PM 2.5 blowing in on the
north wind every winter from coal fired power plants.
For RMB ¥75 + shipping SmartAIR sent me this 296 mm² HEPA filter at
and I got a pre-filter and carbon filter in case of excessive dust or toxic fumes,
e.g., aldehydes from cheap paint & carpet glue.
Seal the HEPA filter inside the box,
orienting the accordion folds vertically.
Cut a horizontal slit near the top of the box, narrower than the hose
diameter and just wide enough to expose all the accordion folds. Take
care not to cut the HEPA filter.
Flange the hose ends and attach to the face mask cheeks.
Slit and spread the hose middle and attach to the HEPA box slit.
Make durable and air tight with duct tape and staples.
Wear the HEPA box as a backpack or even in or over your backpack.
Perhaps rain-proof it with a plastic bag and cut air inlets in back.
The face mask left and right air inlets are in the cheeks and the
outlet is the original flap valve.
Keep the HEPA box inlet safe from rain, mud and dust.
I like the Sci-Fi look — may we all purify our precious air supply!
- HEPA filter
- Face mask with valve
- Flexible breathing hose, maybe 1 m long and 1 or 2 cm wide
- The box the HEPA filter came in or some similar container
- Duct tape
- Staples & stapler
- Scissors or some similar cutting tool
One Thursday evening in Dim Sum Labs, Hong Kong
Relays and coils present an inductive load whose massive kickback voltage will fry the semiconductors in your power supply so please use batteries instead!
The relay above operates as a NOT gate, wired to oscillate by
connecting the output to the input, chasing its own tail.
Old computers, telephone switches, elevator controllers and the like
are made of relays arranged in series, parallel and feedback circuits.
Whether made of transistors, vacuum tubes, relays, gears, billiard balls
bouncing off each other or dominoes falling, they're all variations on
the same basic theme, simple elements combined in complex ways.
Wood, nails, magnet wire (copper insulated with varnish) and sheet
metal worked with saw, hammer, file and tin snips are all we need to
make sparking clanking logic gates, memory registers, adders,
multipliers, Bitcoin miners, ... um, ok, we'd need an airplane hangar
for those last two.
Theory & design principles:
One morning in ShenZhen, China
Black Beauty Watermelon in season