Here is the remote control tester circuit. This circuit is really a simple and easy tester for verifying the basic operations of an infrared remote control unit. It is low-cost and very easy to construct.

The tester is designed around infrared receiver module TSOP1738. Operation of the remote control is identified by a tone from the buzzer. The circuit is sensitive and has a range of about 5 metres. The integrated IR receiver detects, amplifies and demodulates IR signals from the remote control unit. The piezobuzzer connected at its output sounds to tell us the existence of transmission from the remote control unit.

As displayed in above circuit diagram, output pin 3 of IR receiver module TSOP1738 (IRX1) normally stays high and the piezobuzzer is in silent mode. When the IR module IRX1 receives an infrared signal, its output is going low and, because of this, the piezobuzzer sounds to signify the reception of transmission from the remote (for example television remote control unit).

Power supply for the circuit is taken from the mains making use of a capacitive potential dropper, a half-wave rectifier, a shunt regulator and related parts. Ensure that capacitor C1 is of X2 type. Work with a appropriately small enclosure for making the unit handy.

Assemble the circuit on a general purpose PCB and enclose inside a box. Ensure that the IR receiver module is positioned around the front panel of the box/cabinet so that it can get the IR signals easily. Well, before soldering/connecting the shunt regulator and IR module, please check up the following TL431 and TSOP1738 pin configuration.

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This is the circuit diagram of white line follower toy. The actuator of the toy is the DC motor. This circuit can be used for?a toy car to follow a white?line, this circuit also known as very simple robot: “line follower without microcontroller”. The motor is either a?3v type with gearing to?steer the car or a rotary?actuator or a servo motor.

How the circuit work..?

When equal light is detected by the photo resistors the voltage on the base of the first transistor will be mid rail and the circuit is adjusted via the 2k2 potensiometer so the motor does not receive any voltage. When one of the LDR’s receives more (or less) light, the motor is turned on / activated. And the same thing will be happen when the other LDR receives less or more light.

You can see the below video as the result of this circuit project:

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Tone Detector diagram 1

Tone Detector diagram 2

Tone Detector diagram 3

Tone Detector diagram 4

Tone Detector diagram 5

Circuit source: Sound activated switch for robot

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This is a simple and low cost dew sensor circuit that can be used to switch off any gadget automatically in case of excessive humidity. Dew (condensed moisture) adversely affects the normal performance of sensitive electronic devices.

The main part of this circuit is a low cost dew sensor element (resistor type). Although dew sensor elements are widely used in video cassette players and recorders, these may not be easily available in local market. However, the same can be procured from authorised service centres of reputed companies. The author used the dew sensor for FUNAI VCP model No. V.I.P. 3000A (Part No:6808-08-04, reference no. 336) in his prototype. In practice, it is observed that all dew sensors available for video application possess the same electrical characteristics irrespective of their physical shape/size, and hence are interchangeable and can be used in this project.

This simple and low cost dew sensor circuit is basically a switching type circuit made with the help of a popular dual op-amp IC LM358N which is configured here as a comparator. (Note that only one half of the IC is used here.) Under normal conditions, resistance of the dew sensor is low (1 Kohm or so) and thus the voltage at its non-inverting terminal (pin 3) is low compared to that at its inverting input (pin 2) terminal. The corresponding output of the comparator (at pin 1) is accordingly low and thus nothing happens in the circuit.

When humidity exceeds 80%, the sensor resistance increases rapidly. As a result, the non-inverting pin becomes more positive than the inverting pin. This will push up the output of IC1 to a high level. As a consequence, the LED inside the optocoupler is energised. At the same time LED1 provides a visual indication. The optocoupler can be used to any electronic device for switching purpose.

This circuit uses a low voltage, low current power supply unit. The diode D1, resistors R8 and R6 and capacitor C1 do the job. This simple power supply module obviates the requirement for a bulky and expensive step down transformer.

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This is the simple circuit of proximity infrared detector, proximity sensor based? infrared. The applications of this circuit are the most varied. From placing it in the front door to prevent people stop in front of this circuit, or even placing it in the back and front of the car to warn other drivers when they get too close to the park.

The circuit operation is based on emitting a burst of infrared light signals which bounce off the close object is received by another component. When received the system detects proximity with the LED output is activated (shines).

The integrated circuit is a generator / decoder tones that well meets the needs of this design. Both the photodiode and phototransistor be situated with units suitable approach to improve the range. With simple LED reflectors are available scope of the order of meters. With convex lens can cover distances of five meters. It is convenient to sacrifice some range but placing UV filters and SUNLIGHT which do not let the phototransistor (receiver element) sunlight.

The power of this circuit can be any voltage between 5 and 9 volts.

To drive external circuitry will suffice to replace the LED by an optocoupler, which actuated by means of its internal transistor circuit to be controlled.

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Here is the simple and low cost light alarm circuit built using timer IC 555 as the sound generator and a LDR to sense the environment light. This alarm is activated when the light beam on the LDR photocell is interrupted (You can use the light of a flashlight bulb which will make you a source for remain on, this may be 3 volts, no matter whether AC or DC).

Components List:

Capacitor:
C1: .1 uF

Resistor:
R1: 100K (potensiometer)
R2: 1K
R3: 47K
R4: 100K
R5. 27 ohm
R6: 220 ohm

Semiconductor:
IC1: 555
TR1: 2N3055, C1060 or C1226
D1: 1N4002

Others:
Speaker 8 or 16 ohms
1 LDR / photocell

When the LDR / photocell is receiving light, has low resistance, thus blocking the positive voltage that gives R4 to terminal 4 of IC 555, maintaining multivibrator off and the speaker does not sound when the photocell stops receiving light, its resistance increases in fraction seconds, which makes it reaches the above positive voltage to the terminal, which activates the alarm.

Circuit Note: The LDR should not receive another light than that which serves to activated.

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This is the electronic circuit diagram of aquarium temperature probe capable to monitor the temperature of water and indicate the rise in temperature through audio-visual indicators. This circuit uses diode 1N34 as the temperature sensing probe. The resistance of the diode will be vary depends on the temperature in its vicinity.

The environmental factors including light and temperature affect fish culture. The temperature of water has profound effect because fish cannot breed above or below the critical temperature limits. Temperature between 24?C and 33?C is found to be the best to induce spawning in fishes. This particular temperature range is also necessary for the healthy growth of nursery fish fries (young fishes). Rise of water temperature due to sunlight may adversely affect the fish rearing process.

How the circuit work:

The diode 1N34 sense the temperature of the water in aquarium. Typically, the diode can generate around 600 mV when a potential difference is applied to its terminals. For each degree centigrade rise in temperature, the diode generates 2mV output voltage. That is, at 5C, it is 10 mV, which rises to 70 mV when the temperature is 35?C. This component is exploited in the circuit to sense the temperature variation in aquarium water.

Since the output from the diode sensor is too low, a high-gain inverting DC amplifier is used to amplify the voltage. CA3140 (IC1) is the CMOS version op-amp that can operate down to zero-volt output. The highest output available from IC1 is 2.25V less than the input voltage at pin 7. With resistor R4 and VR2, the variation in diode voltage can be amplified to the required level. Resistor R1 restricts current flow through diode D1 and preset VR1 (1-kilo-ohm) sets the input voltage at pin 3. IC3 (7805) provides regulated 5 volts to the inputs of IC1, so that the input voltage is stable for accurate measurement of temperature.

The output from IC1 is fed to display driver LM3915 (IC2) through preset VR3 (50-kilo-ohm). With careful adjustments, the wiper of VR3 can provide 0-400 millivolts to the input of IC2. The highly sensitive input of IC2 accepts as low as 50 mV if the reference voltage at its pin 7 is adjusted using a variable resistor. To increase the sensitivity of IC2, preset VR4 is connected at one end to ‘reference voltage end’ pin 7 and its wiper is connected to ‘high end’ pin 6 of the internal resistor chain.

When approximately 70 mV is provided to the input of IC2 by adjusting preset VR3, LED1 (green) lights up to indicate that the temperature is approximately 35?C, which is the crossing point. When the input receives 100 mV, LED2 (red) lights up to indicate approximately 50?C. Finally, the buzzer starts beeping if the input receives 130 mV corresponding to a temperature of 65?C.

In short, LEDs and the buzzer remain standby when the temperature of the water is below 35?C (normal). With each step increase of 30 mV in the input (corresponding to 15?C rise in temperature), LEDs and the buzzer become active.

Pin 16 of IC2 is used to drive the piezobuzzer through transistor T1. When pin 16 of IC2 becomes low, T1 conducts to beep the piezobuzzer. Resistor R7 keeps the base of transistor T1 high to avoid false alarm. IC4 provides regulated 9V DC to the circuit.

Build the circuit on a common PCB and mount in a suitable box. Glass signal diode D1 is immersed in water to sense the temperature of water. Its leads should be coated with enamel paint to avoid shorting in water. Alternatively, enclose the diode in a small glass tube or test tube having sufficient internal space to fit the diode. Make the sensor assembly waterproof using wax or other method to ensure there is no short circuit because of the water.

Take care while calibrating and setting the circuit. With 5V DC supply to diode D1 and an ambient temperature of about 35?C, D1 generates around 70 mV. Adjust VR3 until the voltage in its wiper increases to 70 mV, so that the input of IC2 (pin 5) receives 70 mV corresponding to the diode output voltage at 35?C. At this stage, green LED1 should turn on. If it doesn’t, adjust VR4 until LED1 just lights up. Immerse the diode in temperature adjusted hot water (35?C) and adjust VR3 and VR4 until green LED1 lights up. Increase the water temperature to 50?C by adding hot water. Now red LED2 will glow. At this position, the voltage at pin 6 of IC1 will be around 100 mV. When the temperature of water increases further to 65?C, the buzzer starts beeping. After calibration, immerse the diode assembly in the aquarium tank just below the water surface and fix it permanently to avoid floating.

Source: EFY Mag
Good luck

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This kind of circuit is a helpful device for testing of infrared (IR) based remote control transmitters utilized for TVs and VCRs and so forth. The IR motions from a remote control transmitter are sensed by the IR sensor module in the analyzer and its output at pin 2 goes low. This thusly switches on transistor T1 and reasons LED1 to squint. In the meantime, the signal beeps at the same rate as the approaching signs from the remote control transmitter. The pressing of diverse catches on the remote control will bring about distinctive beat rates which might change the rate at which the Led eye flickers or the ringer beeps.

The point when no sign is sensed by the sensor module, output pin 2 of the sensor goes high and, accordingly, transistor T1 switches off and thus LED1 and signal BZ1 go off. This circuit obliges 5v controlled power supply which could be gotten from 9V eliminator and joined with the circuit through a jack.

Capacitor C1 smoothes DC input while capacitor C2 stifles any spikes showing up in the input supply.

Legitimate crushing of the metal case will guarantee that the electromagnetic outflows which are transformed by tube-lights and electronic balances and so forth (which lie inside the data transmission of collector circuit) and rehashes the steps demonstrated in step 1 above and notes down his new score (say, X2). He includes this score to his past score. The same method is rehashed by player “Y” in his turn. 4. The diversion carries on until the score achieved by one of the two players adds up to up to or surpasses 100, to be announced as the victor.

A few players can partake in this amusement, with each one getting an opportunity to score throughout his own particular turn. The circuit may be collected utilizing a multipurpose board. Fix the showcase (LEDs and 7-portion show) on top of the bureau plus the three switches. The supply voltage for the circuit is 5v. are successfully crushed and don’t meddle with the working of the circuit. The proposed layout of the crate holding the circuit is demonstrated in the figure. The 9v DC supply from the eliminator might be bolstered into the jack utilizing a banana kind of plug.

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Here the water-level indicator which use a 7-segment display, to show the water level (low, half and full) in the tank. Moreover, a buzzer is utilized to warn you of water overflowing from the tank. The circuit shows the water level by displaying L, H and F for low, half and full, respectively.

The circuit utilized five sensors to detect the different water levels in the tank. Sensor A is connected to the negative terminal (GND) of the power supply. The other four sensors (B through E) are connected to the inputs of NOT gate IC 7404. When there is a high voltage at the input pin of the NOT gate, it outputs a low voltage. Similarly, for a low voltage at the input pin of the NOT gate, it outputs a high voltage.

When the tank is empty, the input pins of IC 7404 are pulled high via a 1-mega-ohm resistor. So it outputs a low voltage. As water starts filling the tank, a low voltage is available at the input pins of the gate and it outputs a high voltage.

When the water in the tank rises to touch the low level, there is a low voltage at input pin 5 of gate N3 and high output at pin 6. Pin 6 of the gate is connected to pin 10 of gate N9, so pin 10 also goes high. Now as both pins 9 and 10 of gate N9 are high, its output pin 8 also goes high. As a result, positive supply is applied to DIS3 and it shows “L” indicating low level of water in the tank.

Similarly, when water in the tank touches the half level, pins 4 and 5 of AND gate N8 become high. As a result, its output also goes high and DIS2 shows “H” indicating half level of water in the tank. At this time, pin 9 of gate N9 also goes low via gate N4 and DIS3 stops glowing.

When the water tank becomes full, the voltage at pin 1 of gate N1 and pin 3 of gate N2 goes low. Output pin 3 of gate N7 goes high and DIS1 shows “F” indicating that the water tank is full.

When water starts overflowing the tank, pin 13 of gate N6 goes low to make output pin 12. The buzzer sounds to indicate that water is overflowing the tank and you need to switch off the motor pump.

Build and construct the circuit on a general-purpose PCB and enclose in a?appropriate box. Use a non-corrosive material such as steel strip for the five sensors and hang them in the water tank as shown in the circuit diagram. Use regulated 5V power supply or battery to power the circuit.

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This is the cell phone shield circuit which can be used as mobile charger. Give protection to your cell phone from unexpected use or theft working with this easy circuit. It is able to produce a loud chirping sound when someone tries to take away the mobile handset. The added function is that the circuit also operates as being a mobile charger.

The circuit is powered by a step-down transformer X1 with rectifier diodes D1 and D2 and filter capacitor C1. Regulator IC 7812 (IC1) together with noise filter capacitors C2 and C3 gives regulated power source.

The cell phone shield circuit uses two NE555 timer ICs: One as being a very simple astable multivibrator (IC2) and then the 2nd as being a monostable multivibrator (IC3). The astable multivibrator has timing resistors R1 and R2 but no timing capacitor since it operates with stray capacitance. Its pins 6 and 2 are directly joined to a safeguarding shield built up of 10cm?10cm copper-clad board.

The inherent stray capacitance of the circuit is enough to supplied an output frequency of about 25 kHz with R1 and R2. This arrangement gives better sensitivity and allows the circuit with hand capacitance effect. Output pulses from the oscillator are immediately assigned to trigger pin 2 of the monostable multivibrator. The monostable utilizes a low-value capacitor C6, resistors R3 and preset VR1 for timing.

The output frequency of the monostable multivibrator is altered utilizing preset/trimmer VR1 such that it is slightly less than that of the astable multivibrator. This makes the circuit standby, as soon as there is no hand capacitance present. So in the standby mode, the astable”s output is going to be low. This tends to make the trigger input of monostable become low and output become high.

The warning indicator buzzer and LED1 are joined such that they come to be active only when the output of the monostable multivibrator sinks current. During the standby state, the LED1 continues to be “off” and also the buzzer is silent. As someone attempts to take the cell phone from the defending shield, his hand comes close to the shield or makes contact with the shield, which introduces hand capacitance within the circuit. Because of this, the astable”s frequency changes, which makes the trigger pin of the monostable become low and its output oscillates. This generates chirping sound from the buzzer and also makes the LED1 blink.

The circuit can even be utilized as being a mobile charger. It delivers output of 6V at 180 mA through regulator IC 7806 (IC4) and resistor R5 for charging the cell phone. Diode D3 defends the output from polarity reversal.

The circuit could be wired on a general PCB. Enclose it inside a appropriate case with provision for charger output leads. Produce the protective shield making use of 10cm?10cm copper-clad board or aluminium sheet. Hook it up towards the circuit working with a 15cm plastic wire. Leads of all capacitors ought to be short.

Fine-tune VR1 little by little working with a plastic screwdriver until eventually the buzzer stops sounding. Get the hand nearby to the shield and fine-tune VR1 right up until the buzzer sounds. With trial-and-error method, set it up for the highest level of sensitivity such that as shortly the hand comes close to the shield, the buzzer begins chirpring and also the LED blinks. As an alternative to applying the copper cladding for shield, a metallic cell phone holder can be utilized as being the shield.

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