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PIC-Based Water Tank Level Meter Pt.2

Last month, we published the circuit of the Water Tank Level Meter and described how it worked. This month, we show you how to build both the basic and telemetry versions and detail the installation.

by John Clarke

Both the basic and telemetry versions of the Water Tank Level Meter use the same PC board (code 04111071, 104 x 79mm). This is housed in a 115 x 90 x 55mm sealed polycarbonate enclosure with a clear lid.

Basically, the telemetry version uses a handful of extra parts, among them a 433MHz transmitter module and two BCD rotary switches. It also uses parts that are salvaged from a solar garden light. These include the solar cell, a single AA NiMH or NiCd cell and the Schottky diode which is used for diode D2.

Click for larger image
Fig.9: follow this parts layout diagram to build the basic version of the Water Level Meter. The pressure sensor is shown mounted on the board here but could also be in installed in a separate box that sits on the bottom of the tank.

This is by far the cheapest way to obtain the solar cell and you also will have some spare parts such as a white LED driver, a white LED and garden light hardware components.

Typically single solar garden lights cost around $10. Don’t be tempted to get the multi-pack solar garden lights that sell for around $5 or less per light. These generally use lower quality solar cells.

Before removing the parts, it’s a good idea to first charge the NiMH or NiCd cell by placing the garden light in the sun for a few hours. Don’t forget to remove the insulation tab from the battery before doing this, otherwise it will never charge.

Once that’s done, you can remove the solar cell, the rechargeable AA cell and the 1N5819 Schottky diode (or equivalent).

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