Clap Sensitive On Off Relay Diagram Circuit

This circuit was intended to activate a relay by means of a hand clap. Further claps will turn-off the relay. An interesting and unusual feature of this project is the 3V battery operation. The circuits sensitivity was deliberately reduced, in order to avoid unpredictable operation. Therefore, a loud hand clap will be required to allow unfailing on-off switching. Q1 acts as an audio amplifier. IC1 timer, wired as a monostable, provides a clean output signal and a reasonable time delay in order to allow proper switching of the following bistable circuit. A discrete-components circuit formed by Q2, Q3 and related parts was used for this purpose, in order to drive the Relay directly and to allow 3V supply operation.

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Circuit Diagram:

Clap Sensitive on-off Relay Circuit Diagram

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Parts:

R1 = 12K
R2 = 1M
R3 = 6.8K
R4 = 220K
R5 = 2.2M
R7 = 100K
R8 = 22K
R9 = 6.8K
R10 = 100K
Q1 = BC550C
Q2 = BC328
Q3 = BC328
C1 = 220nF-63V
C2 = 22nF-63V
C3 = 220nF-63V
C4 = 22nF-63V
C5 = 22nF-63V
C6 = 47uF-25V
D1 = 1N4148
D2 = 1N4148
B1 = 3V Battery
IC1 = 7555 CMos IC
RL1 = DIL Reed-Relay SPDT
SW1 = SPST Switch
MIC1 = Electret Mic

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Notes:

A small DIL 5V reed-relay was used in spite of the 3V supply. Several devices of this type were tested and it was found that all of them were able to switch-on with a coil voltage value comprised in the 1.9 - 2.1V range. Coil resistance values varied from 140 to 250 Ohm. Stand-by current consumption of the circuit is less than 1mA. When the Relay is energized, current drain rises to about 20mA.

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On And Off Button Diagram Circuit

In this simple circuit we give the chip a little more attention than usual. It is astonishing what can be built with a 555. We are always infatuated with simple circuits using this IC, such as the one shown here. The 555 is used here so that a single push-button can operate a relay. If you press the button once, the relay is energized. When you press it again the relay turns off. In addition, it is possible to define the initial state of the relay when the power supply is switched on. The design is, as previously mentioned, very simple. Using R1 and R2, the threshold and trigger inputs are held at half the power supply voltage.

Circuit diagram:

On/Off Button Circuit Diagram

When the voltage at the threshold pin becomes greater that 2/3 of the power supply voltage, the output will go low. The output goes high when the voltage at the trigger input is less than 1/3 of the power supply voltage. Because C2, via R3, will eventually have the same level as the output, the output will toggle whenever the push-button is pressed. If, for example, the output is low, the level of the trigger input will also become low and the output will go high! C1 defines the initial state of the relay when the power is applied. If the free end of C1 is connected to Vcc, then the output is high after power up; the output is low when C1 is connected to ground.

Author: Ger Langezaal - Copyright: Elektor Electronics

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Simple Auto Turn Off Battery Charger Circuit Diagram

This Auto Turn-Off Battery Charger Circuit Diagram for series-connected 4-cell AA batteries automatically disconnects from mains to stop charging when the batteries are fully charged. It can be used to charge partially discharged cells as well. The circuit is simple and can be divided into AC-to-DC converter, relay driver and charging sections. In the AC-to-DC converter section, transformer X1 steps down mains 230V AC to 9V AC at 750 mA, which is rectified by a full-wave rectifier comprising diodes D1 through D4 and filtered by capacitor C1. Regulator IC LM317 (IC1) provides the required 12V DC charging voltage.

 Auto Turn-Off Battery Charger Circuit Diagram

When you press switch S1 momentarily, the charger starts operating and the power-on LED1 glows to indicate that the charger is ‘on.’ The relay driver section uses pnp transistors T1, T2 and T3 (each BC558) to energise electromagnetic relay RL1. Relay RL1 is connected to the collector of transistor T1. Transistor T1 is driven by pnp transistor T2, which, in turn, is driven by pnp transistor T3. Resistor R4 (10-ohm, 0.5W) is connected between the emitter and base of transistor T3.

When a current of over 65 mA flows through the 12V line, it causes a voltage drop of about 650 mV across resistor R4 to drive transistor T3 and cut off transistor T2. This, in turn, turns transistor T1 ‘on’ to energise relay RL1.


Now even if the pushbutton is released, mains is still available to the primary of the transformer through its normally open (N/O) contacts.  In the charging section, regulator IC1 is biased to give about 7.35V. Preset VR1 is used for adjusting the bias voltage. Diode D6 connected between the output of IC1 and battery limits the output voltage to about 6.7V, which is used for charging the battery.  Pushing switch S1 latches relay RL1 and the battery cells start charging. As the voltage per cell increases beyond 1.3V, the voltage drop across resistor R4 starts decreasing. When it falls below 650 mV, transistor T3 cuts off to drive transistor T2 and, in turn, cuts off transistor T3.

As a result, relay RL1 de-energises to cut off the charger and red LED1 turns off.  You may determine the charging voltage depending on the NiCd cell specifications by the manufacturer. Here, we’ve set the charging voltage at 7.35V for four 1.5V cells. Nowadays, 700mAH cells are available in the market, which can be charged at 70 mA for 10 hours. The open-circuit voltage is about 1.3V. The shut-off voltage point is determined by charging the four cells fully (at 70 mA for 14 hours). After measuring the output voltage, add the diode drop (about 0.65V) and bias LM317 accordingly.

Author : Y.M. Anandavardhana

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