Digital Tank Level Indicator shows up to 97 discrete water levels in the tank, which can also be changed by adjusting pot VR1. Digital Tank Level Indicator is especially suited for apartments, hostels, hotels, etc. where many taps are connected to one tank. In such cases, if someone forgets to close the tap, this circuit would alert the operator well in time.
Digital Tank Level Indicator uses just a two-core cable to monitor various water levels and corresponding readings on 7- segment display. The circuit operation is based on timer IC3 & IC4 and decade counter cum seven-segment display IC1 & IC2.
About the Circuit :
As shown in the circuit diagram IC1 & IC2 forms two- digit frequency counter. The clock pin1 and CE (Clock Enable) pin2 are used in such a way that the counter advances when pin1 is held high and pin2 undergoes a high-to-low transition.
IC4 is used as an astable multivibrator, which generates continuous 30Hz clock pulses .The output of IC4 at pin3 is connected to CE pin2 of IC1.
The other timer IC3 is used as a timing pulse generator. The different duration of high and low periods of the timing pulses are achieved because of the charging and discharging paths for the timing capacitor C2 differs.
During positive duration of timing pulse at pin1 of IC1, the frequency counter is allowed to count the number of negative going pulses which are continuously available at its pin2. This counting is displayed on DIS1 and DIS2. However, at the end of positive pulse, the frequency counter is latched. During the following 4 seconds low-level period, display will show the current count. At beginning of the next positive pulse, the frequency counter resets and starts counting afresh.

Thus, this digital meter shows reading for 4 seconds duration and then goes off for a variable period of 0.5 sec to 3 sec. By adjusting preset VR2, the low duration pulse period  (4sec) can be set. The low pulse duration should invariably greater than 3 sec. Here Red LED D4 gives the visual indication that the clock pulses are generated whereas glowing of Green LED D3 indicates the timing of pulse generation.
VR1 is a linear wire-wound pot, is fitted in such a way that minimum and maximum water levels can be achieved by the movement of pot shaft. Preset VR2 and VR3 are to increase the sensitivity of the frequency count.
Note on Output Result :
When power is on, the first counter output represented on 7-segment display may be random number due to timing adjustments. Nevertheless, at the next counting it will show the correct results or the correct output level.

Digital Tank Level Indicator shows up to 97 discrete water levels in the tank, which can also be changed by adjusting pot VR1. Digital Tank Level Indicator is especially suited for apartments, hostels, hotels, etc. where many taps are connected to one tank. In such cases, if someone forgets to close the tap, this circuit would alert the operator well in time.
Digital Tank Level Indicator uses just a two-core cable to monitor various water levels and corresponding readings on 7- segment display. The circuit operation is based on timer IC3 & IC4 and decade counter cum seven-segment display IC1 & IC2.
About the Circuit :
As shown in the circuit diagram IC1 & IC2 forms two- digit frequency counter. The clock pin1 and CE (Clock Enable) pin2 are used in such a way that the counter advances when pin1 is held high and pin2 undergoes a high-to-low transition.
IC4 is used as an astable multivibrator, which generates continuous 30Hz clock pulses .The output of IC4 at pin3 is connected to CE pin2 of IC1.
The other timer IC3 is used as a timing pulse generator. The different duration of high and low periods of the timing pulses are achieved because of the charging and discharging paths for the timing capacitor C2 differs.
During positive duration of timing pulse at pin1 of IC1, the frequency counter is allowed to count the number of negative going pulses which are continuously available at its pin2. This counting is displayed on DIS1 and DIS2. However, at the end of positive pulse, the frequency counter is latched. During the following 4 seconds low-level period, display will show the current count. At beginning of the next positive pulse, the frequency counter resets and starts counting afresh.

Thus, this digital meter shows reading for 4 seconds duration and then goes off for a variable period of 0.5 sec to 3 sec. By adjusting preset VR2, the low duration pulse period  (4sec) can be set. The low pulse duration should invariably greater than 3 sec. Here Red LED D4 gives the visual indication that the clock pulses are generated whereas glowing of Green LED D3 indicates the timing of pulse generation.
VR1 is a linear wire-wound pot, is fitted in such a way that minimum and maximum water levels can be achieved by the movement of pot shaft. Preset VR2 and VR3 are to increase the sensitivity of the frequency count.
Note on Output Result :
When power is on, the first counter output represented on 7-segment display may be random number due to timing adjustments. Nevertheless, at the next counting it will show the correct results or the correct output level.