Household water meters readings Repeater

The proposed device offers the possibility to duplicate the indications of room counters of flow of hot and cold water, often installed in a very inconvenient for reading. It can also be used for other purposes, such as a counter of turns of parts on the Assembly line or count visitors.

Figure. 1

The inconvenience of reading mechanical water meters has led me to the decision to create their electronic repeater. This device I decided to collect on my existing microcontroller PIC16F84A-04/P and the two-line LCD MT-16S2D. Diagram of the repeater shown in Figure. 1.

Household counters of hot and cold water, having a name index And is equipped with a reed switch, which closes and razlychayutsya when passing through the meter a certain portion of water. For example, the counters of SV-15ИХ and SV-15ИГ this happens every ten liters. In series with the reed switch and in parallel to each sensor installed resistors, so the resistance of the reference circuit when open reed switch is about 6 kω, and when closed is about 1 kOhm. This is done in order to remote meter readings could automatically detect the open or short circuit of a connector.

In this device the ability to automatically control fault not used. But to ensure a reliable fixation of the microcontroller the state of the reed switches, I had to consistently include in their circuit the resistors R1 and R2. Because the microcontroller resistors connecting the input with the positive supply, have considerable variation of resistance of the resistors R1 and R2, may have to pick up.

In the program of the microcontroller is organized in two independent counter circuits with reed. Each circuit adds to the content of the corresponding counter ten liters. Accumulated values are displayed on the indicator is in cubic meters (Fig. 2). There are also buttons (SB1, SB2 — counter cold water and SB3, SB4 — counter hot water), the taps on which in the beginning of the repeater to achieve the coincidence of his testimony with the testimony of the mechanic.

Fig. 2

Nourish the device from the battery GB1 of the four battery cells size AA. It consumes them from the current 2.5 mA. The performance of the microcontroller, according to his passport, is maintained at a voltage of from 3 to 6 V. One battery set is enough for two or three years of continuous operation (without illumination of the indicator). Accumulated in the capacitor C4 charge is enough to keep the device within 30 seconds after disconnecting the battery. This time is sufficient for the spent elements. Powering the device is possible and from any source of voltage of 5 V.

Repeater assembled on a printed circuit Board, drawing which is shown in Fig. 3. Its length and width are the same dimensions used LCD, to connect which it connector. The control buttons can be mounted on a Board or put them on the front panel of the instrument housing.

Fig. 3

Assembled without errors, the device starts to work immediately. Just need to adjust the setup resistor R4, the contrast of the image on the display, and buttons SB1—SB4 to set it equal to the readings of water meters at the moment.

Archives of the project

Author: N. KAMENEV, Moscow
Source: Radio log No. 12/2015