Water Quality Project

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  • Problem: Bad water quality 
  • Solution: Easy-access water quality testing tool
  • Partners: Phutung Research Institute, Amsterdam University of Applied Sciences
  • Impact: 600 municipalities

Drinking water contamination is a major health issue in Nepal. Tools to assess drinking water quality are expensive and not widely available. To address this problem, Diyalo has put  the Phutung Research Institute (PRI) in contact with young experts at the Amsterdam University of Applied Sciences (HvA). Together, PRI and HvA will develop a low cost and portable optical device to detect contaminants in drinking water. Once developed, PRI plans to distribute the device to 600 municipalities within Nepal in coordination with the national government.

Achieved during the project:

1) Review of the initial design ✔️

2) Improve and redesign where necessary ✔️

3) Detailed design; Theory + Simulations ✔️

4) Implementation and testing ✔️

5) PCB design, fabrication and testing ✔️

Delivered and tested:

An amplifier system to help in measuring up to, and preferably beyond, 10ppb of TLF in drinking water. From 500ppb down to 10ppb, which translates to 39.95nA to 0.787nA respectively. Amplified to a range within the specs of the ADC being used. ✔️

Conclusions; The Take-Aways Amplifier system
An amplifier system has been designed and produced to transform 0.787nA – 40nA to within a range of 0 to 3.3V, where it can reliably measure the sensor signals to an amount deemed sufficient when using a faraday cage shielding it. 

Conclusions; The Take-Aways Thermal Management
The calculations done indicate that the IN-C39ATK UVC LED can theoretically be kept within the specifications of a maximum of 65°C at the maximum specified supply current of 150mA, at an ambient temperature of 25°C, by implementing a low-cost two layer PCB with the use of fourteen filled-thermal vias with a diameter of 0.2mm and an appropriate heatsink.

Recommendations; What Can Be Improved? Amplifier system

  • A dual op. amp. was chosen in the first amplifier stage, because of the specifications and availability, note that this could be replaced with an op. amp. package housing a singular one. This could potentially reduce the cost by $1 per system. 
  • The PCB has certain ‘Faraday cage-esque’ qualities, because of the internal and external ground planes. It could be valuable to look into burying the signal in between two ground planes. 
  • The PCB could also employ a Faraday cage on the PCB itself, which would allow for an end product with a non-conducting case.

Recommendations; What Can Be Improved? Thermal Management

  • It is advised not to continue to calculate the heat at the photodiode, but to measure it experimentally, as lots of variables of high importance that can not be taken into consideration. From this, specifications can be withdrawn and the steps taken in the paper can be followed for restricting the heat to the photodiode.
  • Simulations should be done. (Autodesk Fusion 360)
  • The use of MCPSBs could be considered, if stricter requirements are posed on the maximum temperature.
  •  Further research could be done on thermal compounds, if the heat sink chosen does not have an included heat pad. 
  • The electronics driving the UVC LED could heat up due to heat through the same PCB. The 65°C limit will most likely not be of much trouble, but it is imperative to take this into consideration nonetheless. 

*See the paper for any details

20210723 Water quality – thermal_management