I added a couple pieces of wood to raise to work level to where the particle-free breeze is blowing.

I am delighted with the HEPA air source performance for sterile transfers. I was able to transfer mycelium from petri dish to syringe to culturing jars without contamination. I was also able to pour agar from a flask into petri dishes without any contamination. This perfect outcome was not possible using my still air box.

I have struggled with using a still-air box (plus bleach spray, gloves, and sleeves) for sterile work with spotty success. So I decided to obtain a HEPA air source. Sticker shock → build my own.
I used a hammock filter as a pre-filter.That way, it could be big, minimizing back-pressure. Here is the HEPA air source half finished.
I used hardware cloth (coarse galvanized screen) held in place by wood chips and Weldwood contact adhesive to hold the cut hammock filter in place.

I decided to replace the old under-the-cabinet fluorescent lamp (hasn't worked in years) with an adhesive-backed LED strip (warm white from Ebay - $7.50 for 5 meters). I got a 12V switching power supply wall wart ($8.00 from Ebay), removed it from the case, and stuck it a wood box (held together with 5-minute epoxy). The box is stuck to the cabinet wood with Weldwood contact cement. The little brackets that help the LED strip stay up are made from 1/16" UHMW.

One can also program a WiFi module from TI using micropython.

The WiPy is a small, ultra-low power and low cost Wi-Fi module
targeted to the Internet of Things.

e2e.ti.com/blogs_/b/connecting

Many makers balk at the prospect of learning C. I can't blame them. Even with extensive comments, C programs written by others can be difficult to wrap one's head around.

Micropython is a maker-friendly option that may work well depending on one's choice of microcontroller.

designnews.com/electronics-tes

@jmwright One more thing about free-hand SM circuit construction: solder paste (and, of course, a really good soldering station) is a must for such small connections. It can be pricey, it needs to be kept in the 'fridge, and it has an expiration date. I got my little syringe tube maybe 4 years ago. Long-expired, it still works well for hand soldering.

I have long had a few ideas that could only be implemented on an FPGA. I only have experience with microcontrollers: a whole different world. I tried to learn Verilog and relevant tool chain. I asked a question on the main Verilog forum (it's been a long time - I forgot which), the main guru there snapped "you need to learn the basics first". I thought I had. Needless to say, I was discouraged. Now I see that some progress is being made on this:

digikey.com/en/articles/techzo

My little, but useful, fungus scraper is shown to the left of a petri dish of fungus that could be scraped. This is a sturdier version of the inoculation loop that microbiologists use.

I cut a strip of stainless, shaped it, stuck it into a stainless tube, forced in a little brazing paste (sra-solder.com/soldering-brazi), then torched it. For this little job, a propane torch might have been sufficient.

Brazing is a useful skill. Nobody showed me. I watched videos, bought stuff, then made mistakes.

This container is for use in working with a terrific new material that I am investigating: a mixture of chopped glass, sodium silicate, and water (more on this in a later post). This mix tends to get lumpy when mixed. I like to press out the lumps to create a more homogeneous mixture. This strong, flat-bottomed container will work well for that.

I created the flat-bottomed, straight-walled container from stainless steel. I used a carbide-infused fiberglass cutting disk mounted to a Dremel for both tasks.

All-State 11 FC Nickel-Silver coated brazing rods seemed like just the ticket, but it didn't work. Finally, I called the local Air Gas (where I get my gas cylinders) who sold me Radnor Safety-Silv 56 coated brazing rods. 😀 I used a natural gas-oxygen torch.

Commercial HEPA flow hoods are expensive. I made a small HEPA filter from a catch basin (Lowes Item # 118877), a vacuum bag, wood, adhesive, and a squirrel cage blower.

I used the wood to mount the filter fabric.. The installed finished assembly works great. By that, I mean that the air flow is what I wanted: not too much or too little.

I discovered thi wonderful book when it was only expensive and hardbound. Now the author has made every chapter of the book available in PDF format - FREE! This book is readable, with a minimum of extraneous (not useful to a maker) math. My most recent insight from this book is that, for slow-changing data, a moving-average filter is most suitable. This is easily implemented on most microcontrollers.

The Scientist and Engineer's Guide to Digital Signal Processing

dspguide.com/

A long time ago, I worked on a vaporizer design that would heat air on-the-fly prior to entering a pipe. The four leftmost objects are casting fixtures. The four little round thingies in the middle are cast ceramic shapes. The right two are fully wired to function as (12V) air heaters. The three things on the right are functional vaporizers - pipe not included. The one on the end is what I have used personally for many years.

otto9otto boosted

The center axle of my top was going to be 4 mm. I am trying to keep everything metric. But a 4 mm drill bit in the center hole of my aluminum master part wobbles. Well, my drawing states that all tolerances are +/- .1 mm, and maybe it is within tolerance, but that wobble doesn't make me comfy. Also, upon examination, 4 mm seem a bit slim. So: I am expanding it to 3/16", but I can't drill it on my lathe - too big. Sweating bullets attempting to exactly center the drill on my drill press.

I have a question: when making a drawing of a disk shape for machining, is it sufficient to draw only one-half of a cross section (with dimensions, of course)? Or, should one draw both cross-section halves, but only dimension one of them?

@jmwright Hi Jeremy, can you tell me what happened to my post wherein I told the tale of my final success in producing a workable DXF file via LibreCAD?

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