Saturday, August 26, 2023

Photosynthesis photography: Making images with living plant leaves

How to make photographs using plant leaves: the technique, examples, f/0.5 camera lens construction, and tips & tricks that I learned along the way.

Inspiration for this project came from a 1970's video made by The Royal Institution:

Starch formation refs:

Video describing inkjet printed photomasks:

A different technique to make leaf prints:

Video from Alpha Phoenix on making photos with cyanotype:

Ray optics simulator:

Giant tweezers:

Anhydrous ethanol:

Hanging basket geranium plant:

Methanol toxicity:  Skin absorption in a quantity high enough to be a problem is rare, according to this.

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Wednesday, July 5, 2023

Measuring the amount of lead (Pb) consumed when drinking from lead crystal glassware. Is it safe?

I show a "DIY" chemical color-based method to determine the amount of lead in water, and then use the method to measure the amount of lead extracted from various types of lead crystal glassware.

Skip to 27:05 to see the detailed results 

Code, analysis, raw data, more references: 

Average daily lead consumption: 50ug in early 1980s, about 2/3 of this came from food and water 

The FDA established a maximum daily intake for Pb called the Interim Reference Level (IRL). The IRL for children and adults is 3 μg/day and 12.5 μg/day, respectively. In 2022, FDA tightened its Interim Reference Levels (IRLs) for lead to 2.2 µg/day for children and 8.8 µg/day for females of childbearing age—a drop of 27% from the original IRLs it established in 2018. 

(2011) The estimated average daily dietary exposure of the French population to lead was 18 μg for adults aged 15 years or more 

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Sunday, May 28, 2023

Multi-layer reactive foil: no fuel, no oxygen, tons of heat

This unusual sheet metal is made of hundreds of nano scale layers of aluminum and nickel. A spark initiates a self-propagating reaction that creates NiAl compound, and lots of heat! This material is used to solder items so fast that the base material doesn't have time to draw heat away from the joint. The technical data sheet indicates that this process is fluxless, and I suspect trying to include flux would cause rapid gas expansion that would blow the solder joint apart. I'm not sure how the solder wets the surface without flux. 

Sunday, April 9, 2023

Temperature-sensing RFID tag in magnetic stir bar

I describe an old project in which a few friends and I designed an RFID tag that fits into a magnetic stir bar and measures temperature wirelessly.  We decided to open-source the project, and you can see the PCB design and tag firmware at the github repo below.  I don't think I have the firmware for the base station, unfortunately.

Sunday, January 22, 2023

Identify chemicals with radio frequencies - Nuclear Quadrupole Resonance (MRI without magnets)


How to build and test an NQR spectrometer, which is similar to MRI, but uses no magnets.  NQR frequencies are unique among all tested compounds, so detecting a resonance indicates a near certainty that a specific chemical is present.

Tektronix 2-series oscilloscope: Video capture was done via VNC client

Zeeman effect shifting optical spectral lines:

Atomic clock calibration using Zeeman effect:

W2AEW's RF tutorial on quarter wave transmission lines:

Water deflected by electric field:

Litz wire only helpful between 50KHz and 1.5MHz -

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Why use vacuum variable capacitors? The parallel LC circuit develops well over 1000 volts during transmit, and they are much easier to finely adjust over a large range.

I've spent quite a few hours making this work since late last year.  I failed to detect a signal from urea, which burned dozens of hours.  Switching to NaNO2 suddenly produced a huge signal.

NQR calculations spreadsheet -

NQR references (many!) :