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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for July 5th, 2021

New version Smart Citizen Kit available | Waag

Posted by jpluimers on 2021/07/05

By now it should be able to order them normally, as this link is from early 2019: [WayBack] New version Smart Citizen Kit available | Waag

An improved 2.1 version of the Smart Citizen Kit is now ready for pre-ordering.

What does the 2.1 version measure?

The Smart Citizen Kit focuses on the weather, sound, light and air quality. The following overview shows the different sensors in version 2.1:

  • Temperature (°C) – Sensirion SHT31
  • Relative humidity (% rh) – Sensirion SHT31
  • Noise level (dBA) – Invensense ICS4342
  • Ambient light (lx) – Rohm BH1721FVC
  • Air pressure (barometer, kPa) – NXP MPL3115A2
  • Equivalent carbon dioxide (CO2 in ppm) – AMS CCS811
  • Volatile organic compounds (ppb) – AMS CCS811
  • Particulate matter (PM1/2,5/10 in μg/m3) – Plantower PMS 5003

Our findings in 2014 showed that the housing can be an important factor by influencing the sensors; there must be sufficient air flow, but also a watertight environment. And the placement is important (not in full sun for example).

Some relevant links and information:



Read the rest of this entry »

Posted in Development, Hardware Interfacing, Power User, Software Development | Leave a Comment »

PLA use outdoors? – 3D Printing Stack Exchange

Posted by jpluimers on 2021/07/05

[WayBack] PLA use outdoors? – 3D Printing Stack Exchange:

TL;DR: though bio-degradable, PLA needs high temperatures (> 50 Celsius) to degrade.

So in European summers, for light weight enclosures (like weather stations or signage), it should be fine.

  • [WayBack] Using PLA for Long-Term Outdoor Applications – IEPAS

    To biodegrade within 90 days, as described, the products have to reach 140 F for 10 consecutive days.  This requires a special facility, which few consumers have access to.  If your PLA products end up at the landfill, they will not degrade any faster than a petroleum-based product.

  • [WayBack] Polylactic acid: Degradation – Wikipedia

    Abiotic PLA degradation is due to 3 mechanisms:[35]

    1. Hydrolysis: The ester groups of the main chain are cleaved, dividing the molecule in two parts, thus reducing molecular weight.
    2. Thermal degradation: A complex phenomenon leading to the appearance of different compounds such as lighter molecules and linear and cyclic oligomers with different Mw, and lactide.
    3. Photodegradation: Sunlight induces degradation due to low-wavelength and high-energy UV radiation. This is a factor mainly where PLA is exposed to sunlight in its applications in plasticulture, packaging containers and films.

    The hydrolytic reaction is:

    {\displaystyle {\ce {-COO + H2O -> – COOH + -OH-}}}

    The degradation rate is very slow in ambient temperatures. A 2017 study found that at 25 °C in seawater, PLA showed no degradation over a year.[36]

    Pure PLA foams undergo selective hydrolysis when placed in an environment of Dulbecco’s modified Eagle’s medium (DMEM) supplemented with fetal bovine serum (FBS) (a solution mimicking body fluid). After 30 days of submersion in DMEM+FBS, a PLLA scaffold lost about 20% of its weight.[37]

    PLA samples of varying molecular weight were degraded into methyl lactate (a green solvent) by using a metal complex catalyst.[38]

    Some bacteria can also degrade PLA, such as Amycolatopsis and Saccharothrix. A purified protease from Amycolatopsis sp., PLA depolymerase, can also degrade PLA. Enzymes such as pronase and most effectively proteinase K from Tritirachium album degrade PLA.[39]

    Degradation is the reverse of the synthesis process in this Wikipedia picture:



For other materials and in-car usage, read:


Posted in 3D printing, Power User | Leave a Comment »

Delphi: TArray of T versus TArray; a function can return the latter, but not the former

Posted by jpluimers on 2021/07/05

I wish I had blogged about this a lot sooner, as then far less people would use var aFoo: array of TFoo as method parameters for results that are just out parameters and could be a function result.

You cannot have array of TFoo as function result, but you can have TArray<TFoo>. The former would be an open array, the latter is a proper array type.

I see many people use var aFoo: array of TFoo with all sorts of SetLength calls before calling and inside a method where a function returning a TArray<TFoo> would be far more appropriate, both in the sense of readability and maintainability.


Posted in Delphi, Development, Software Development | 2 Comments »

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