Category: Maker

Several of my IoT projects use WiFi, and its range is quite limited, too short to be practical for some projects.

There are several alternatives, but the emerging LoRaWAN concept looks interesting and is worth a visit. LoRaWAN is capable of up to 20km range under ideal conditions, km range should be reliable in most cases.

The first trial is to adapt an existing project functional requirement to LoRaWAN connectivity.

Above is a block diagram of the working trial. Continue reading IoT – exploration of LoRaWAN – part 1

Boost converter

The 4-20mA loop used for the water sensor needs a source of 24VDC. This is obtained from the battery (3.6-4.3V) using a DC-DC boost converter which runs only when a measurement is made.

This article discusses related issues. Continue reading IoT water tank telemetry project – part 4

Battery trials

The project continues, albeit slowly.

Some inexpensive DC-DC boost converters have been very slow from China, though multiply source, they have not yet arrived.

An older module which was on hand has enabled progress of reliability and battery trials.

Above is the current prototype. The module on the white plug in cable is a 4-20mA simulator set to 20mA for maximum drain during battery trials. The module at upper right of the pic is a TP4056 batter charger and 1S protection board for the 2000mAh LiPo. The PV array (partially obscured) is capable of 80mA of charge current in full sunlight. The prototype includes a red LED drawing 1mA, an additional 24mAh load per day. Continue reading IoT water tank telemetry project – part 3

Calibration of the 4-20mA input

This article is a tutorial on calibrating the 4-20mA input which is designed for flexibility that is achieved through exploitation of the calibration.

The input device for this tutorial is a Pt100 RTD temperature sensor and inexpensive Chinese Pt100 – 4-20mA converter (loosely) calibrated for -50-150°. The Pt100, the converter, the load resistor, the divider resistors on the MCU board, and the MCu voltage reference all introduce error which is compensated in this end to end calibration procedure.

For this demonstration, two scenarios are measured:

1. probe in still air whose temperature is captured with an accurate thermometer; and
2. probe in boiling water whose temperature is calculated from known altitude and barometric pressure.

Another option would be to use a container of water filled with ice to obtain close to 0° for scenario 1… you don’t need a triple point cell for the end system stability and accuracy.

Temperature of boiling water

Using Calculate cooking time for soft boiled egg :

No, we are not boiling an egg, but the results include the temperature of the boiling water under current altitude and pressure. Continue reading IoT water tank telemetry project – part 2

This is the first in a series of articles describing a simple maker / DIY IoT water tank telemetry system.

Design criteria

• capture water depth, temperature and relative humidity;
• IoT connectivity;
• solar / battery powered;
• wireless connection;
• use existing inexpensive electronic modules.

Design choices made initially:

• 4-20mA water pressure sensor for depth measurement;
• ESP8266 Wemos D1 mini pro for the MCU and wireless elements;
• NodeMCU / Lua software environment;
• external antenna for improved WiFi range;
• 6V 100mA PV array;
• module with TP4056 batter charger and cell protection chip;
• 2500mAh 18650 cell;
• AM2320 temperature and humidity sensor;
• bipolar transistor switch for boost converter;
• Thingspeak RESTful interface for data accumulation and presentation.

Block diagram

Above is a block diagram showing the major system components. Almost all of the electronics is on easily obtained low cost electronic modules source from eBay, assembled on a Veroboard backplane. Continue reading IoT water tank telemetry project – part 1