Water Level Alert Circuit

This is a circuit that can be use when the water contained into a recipient has reached the desired level. This circuit is work with based on 555 timer IC. This is the figure of the circuit.


C1, a 555 CMos timer chip, is wired as an astable multi vibrator whose operating frequency is set by C1, R1 and R2, plus the resistance presented by water across the probes. If the resistance across the probes is zero (i.e. probes shorted), the output frequency will be about 3Hz and the sounder will beep (or the LED will flash) about three times per second. As water usually presents a certain amount of resistance, the actual oscillation frequency will be lower: less than one beep/flash per second. As probes will be increasingly immersed in water, the resistance across them will decrease and the oscillation frequency of IC1 will increase. This means that a rough aural or visual indication of the level reached by water will be available. If a LED is chosen as the alert, C2, D1 and D2 must be added to the circuit in order to double the output voltage, thus allowing proper LED operation (see the rightmost part of the schematics). Interesting features of this circuit are 1.5V supply and ultra-low current consumption: 40µA in stand-by and 0.5mA in operation. This allows a single AAA alkaline cell to last several years and the saving of the power on/off switch.

Part:
R1_______________1K 1/4W Resistor
R2_____________100K 1/4W Resistor (See Notes)
C1_______________2µ2 50V Electrolytic Capacitor
C2_____________220µF 25V Electrolytic Capacitor (See Notes)
D1______________5 or 10mm. Ultra-bright red LED (See Notes)
D2____________1N5819 40V 1A Schottky-barrier Diode (See Notes)
IC1_____________7555 or TS555CN CMos Timer IC
BZ1____________Piezo sounder (incorporating 3KHz oscillator)
B1_____________1.5V Battery (AAA or AA cell etc.)

PWM Motor DC using SG3525

This circuit is design for accurate control of DC motors. DC voltage conversion to a series of pulses, such that the duration of the pulse is a direct proportion to the value of DC voltage. Here’s the figure of the circuit.


This circuit protects against overload and short, PWM range can be adjusted 0-100%, PWM frequency of 100Hz-5KHZ adjusted. Operating voltage of 8 V ~ 35V, minimum current consumption is around 35mA. Maximum current can go to 6.5A. Efficiency better than 90% at full load. There are three trimpot potentiometer, where the function of three trim pots are as follows: VR1: adjust the minimum output voltage VR3: setting the maximum output voltage VR2: setting the output frequency.