On-off Infrared Remote Control Circuit

Description 

Most homes today have at least a few infrared remote controls, whether they be for the television, the video recorder, the stereo, etc. Despite that fact, who among us has not cursed the light that remained lit after we just sat down in a comfortable chair to watch a good film? This project proposes to solve that problem thanks to its original approach. In fact, it is for a common on/off switch for infrared remote controls, but what differentiates it from the commercial products is the fact that it is capable of working with any remote control.

Therefore, the first one you find allows you to turn off the light and enjoy your movie in the best possible conditions. The infrared receiver part of our project is entrusted to an integrated receiver (Sony SBX 1620-52) which has the advantage of costing less than the components required to make the same function. After being inverted by T1, the pulses delivered by this receiver trigger IC2a, which is nothing other than a D flip-flop configured in monostable mode by feeding back its output Q on its reset input via R4 and C3. The pulse that is produced on the output Q of IC.2A makes IC.2B change state, which has the effect of turning on or turning off the LED contained in IC3.

Circuit Diagram:

This circuit is an opto triac with zero-crossing detection which allows our setup to accomplish switching without noise. It actually triggers the triac T2 in the anode where the load to be controlled is found. The selected model allows us to switch up to 3 amperes but nothing should stop you from using a more powerful triac if this model turns out to be insufficient for your use. In order to reduce its size and total cost, the circuit is powered directly from the mains using capacitor C5 which must be a class X or X2 model rated at 230 volts AC.

This type of capacitor, called ‘self-healing’, is the only type we should use today for power supplies that are connected to ground. ‘Traditional’ capacitors, rated at 400 volts, do not really have sufficient safety guarantees in this area. Considering the fact that the setup is connected directly to the mains, it must be mounted in a completely insulated housing. A power outlet model works very well and can easily be used to inter-space between the grounded wall outlet and that of the remote control device.

Based on this principle, this setup reacts to any infrared signal and, as we said before, this makes it compatible with any remote control. On the other hand, it has a small disadvantage which is that sometimes it might react to the ‘normal’ utilization of one of these, which could be undesirable. To avoid that, we advise you to mask the infrared receiver window as much as possible so that it is necessary to point the remote control in its direction in order to activate it.

 Author: Christian Tavernier, Elektor Electronics Magazine
Source http://www.extremecircuits.net/2010/05/on-off-infrared-remote-control.html

07:42 0 comments

Wireless On-Off Switch Circuit

Descriptio 

Normally home appliances are controlled by means of switches, sensors, etc. However, physical contact with switches may be dangerous if there is any shorting. The circuit described here requires no physical contact for operating the appliance. You just need to move your hand between the infrared LED (D2) and the phototransistor (Q1). The infrared rays transmitted by D2 is detected by the phototransistor to activate the hidden lock, flush system, hand dryer or else. This circuit is very stable and sensitive compared to other AC appliance control circuits. It is simple, compact and cheap. Current consumption is low in milliamperes. The circuit is built around an IC CA3140, D2, phototransistor and other discrete components.  
Circuit Diagram:

Parts:

• R1 = 470R
• R2 = 100K
• R3 = 3.3K
• R4 = 10K
• D1 = 1N4007
• D2 = IR LED
• Q1 = L14F1
• RL = 5Vdc Relay
• IC = CA3140
• Q2 = BC548 

Circuit Operation:

When regulated 5V is connected to the circuit, D2 emits infrared rays, which are received by phototransistor Q1 if it is properly aligned. The collector of Q1 is connected to non-inverting pin 3 of IC1. Inverting pin 2 of IC1 is connected to voltage-divider preset R4. Using preset R4 you can vary the reference voltage at pin 2, which also affects sensitivity of the phototransistor. Op-amp IC1 amplifies the signal received from the phototransistor. Resistor R3 controls the base current of transistor BC548 (Q2). The high output of IC1 at pin 6 drives transistor Q2 to energies relay RL1 and switch on the appliance, say, hand dryer, through the relay contacts. The working of the circuit is simple. In order to switch on the appliance, you simply interrupt the infrared rays falling on the phototransistor through your hand. During the interruption, the appliance remains on through the relay. When you remove your hand from the infrared beam, the appliance turns off through the relay. Assemble the circuit on any general-purpose PCB. Identify the resistors through colour coding or using the multimeter. Check the polarity and pin configuration of the IC and mount it using base. After soldering the circuit, connect +5V supply to the circuit.

Source http://www.electronicsforu.com

11:11 0 comments

TV Muter Circuit

Description 

Many households are still graced by tube-type television sets. If you want to connect one of these large tellies to your stereo system to improve the sound quality, this is usually not a problem because there are plenty of SCART to Cinch adapters available in accessory shops. However, with some sets your pleasure is spoiled by the fact that the audio outputs of the SCART connector are not muted during channel switching.

This can sometimes lead to nasty signal spikes, which can cause the loudspeakers of your stereo system to emit irritating popping and cracking noises. In such cases it is a good idea to fit your system with a mute circuit. Fortunately, the right time to activate the mute circuit is defined by the fact that the happy zapper presses buttons on the remote control to switch channels, and the remote control emits IR signals.

There are even inexpensive ready-made IR receiver modules available, such as the TSOP1136 used here, which produce trains of active-low pulses in response to such signals. About the circuit: when no IR signal is present, a capacitor is charged via P2 and a diode. IC1 is a comparator that compares this IR voltage (applied to its non-inverting input on pin 3) to a voltage applied to its other input on pin 2. 

Circuit Diagram:

This reference voltage, which can be adjusted with P1, determines the switching threshold of the comparator. If IC2 receives an IR signal, T2 conducts, and as a result the voltage on C1 drops rapidly below the threshold level set by P1. This causes T1 to change from its previous ‘on’ state to the ‘off’ state. As a result, the relay drops out and the audio link to the stereo system is interrupted for the duration of the noise interval.

It’s all quite simple, as you can see. If you do not have a stabilized 5-V supply voltage available, you can use the circuit at the of the schematic diagram (with a 5-V voltage regulator) together with a simple (unstabilised) AC mains adapter that supplies a voltage in the range of 9 V to 12 V to the 7805 (IC3). You can also use a relay with normally-closed contacts instead of normally-open contacts.

In this case, simply swap the signals on pins 2 and 3 of IC1 so the relay pulls in when an IR signal is received instead of dropping out. This saves a bit of power because the relay is only energized during zapping. If you can’t find any worthwhile use for the second comparator of IC1, it’s a good idea to connect pin 6 to +5 V and pin 5 to ground. To improve noise immunity, you should shield the IR sensor so it is not exposed directly to light from a fluorescent fixture.

Source http://www.extremecircuits.net/2010/05/tv-muter-circuit.html

08:13 0 comments

Infra Red Switch

Description: 

This is a single channel (on / off) universal switch that may be used with any Infra Red remote control that uses wavelengths between 850-950nm.

Circuit diagram 

Notes:

 Any "button" of any remote control may be used to work this universal switch. The button must be pressed for two seconds (determined by R3 and C2) before the relay will operate. Once operated the circuit will remain in this state (latched) until reset. To reset, any button is pressed and held for the delay.

For example, if you were watching TV, and your set was tuned to Channel 3, you could press and hold the TV remote controls channel 3 button for two seconds. That way the TV viewing would not be affected and the relay would activate. You can connect anything to the relay, for example a lamp, but make sure that the relay contacts can handle the rated voltage and current. 

Circuit Operation: 
 IC1 is an Infra Red module. IR modulated pulses are received and buffered by this IC. It has a standard TTL output, the output with no signal is logic 1. One gate of a CMOS inverter and drives Red LED1 as a visible switching aid. Another gate buffers the signal and applies it to the time constant circuit, comprising R3,C2,R4 and D1. C2 charges via R3, and discharges via R4, D1 prevents quick discharge via the low output impedance of the CMOS buffer.

 The pulses are further buffered and contain "jaggered edges" as shown above. These edges are produced by the modulated IR data, which has to be removed. This is achieved using IC3, a 555 timer wired as a monostable, pulse duration R5, C4. These cleanly reconstructs a single clean pulse to activate the bistable latch. A D type flip flop, IC4 is configured as a bistable. The input is applied to the clock pin, the inverted output fed back to the data input and clear and preset lines are tied to ground. For every pulse the relay will operate and latch, the next pulse will turn off the relay and so on. Note that quick turn on and off of the relay is not possible. The output pulse is set at about 1.5 seconds and input delay by R3, C2 set at two seconds.

Parts 

• R1 3k3
• R2 1k
• R3 22k
• R4 220k
• R5 1M
• R6 3k3
• B1 12 V
• D1 1N4148
• D2 1N4003
• Q1 B109
• LED1 CQX35A
• IC1 IR1 available from Harrison Electronics
• IC2 4049
• IC3 CA555
• IC4 SN74HCT74
• IC5 LM7805
• Relay 12 Volt coil with changeover contact
• C1 100u
• C2 22u
• C3 100n
• C4 2u2 

 Author: Andy Collinson
  Source http://www.zen22142.zen.co.uk/

09:48 0 comments

IR Music Transmitter and Reciever

Description 

  Using this circuit, audio musical notes can be generated and heard up to a distance of 10 metres. The circuit can be divided into two parts: IR music transmitter and receiver. The IR music transmitter works off a 9V battery, while the IR music receiver works off regulated 9V to 12V. First diagram shows the circuit of the IR music transmitter. It uses popular melody generator IC UM66 (IC1) that can continuously generate musical tones.

Transmitter circuit diagram:

 The output of IC1 is fed to the IR driver stage (built across the transistors T1 and T2) to get the maximum range. Here the red LED (LED1) flickers according to the musical tones generated by UM66 IC, indicating modulation. IR LED2 and LED3 are infrared transmitting LEDs. For maximum sound transmission these should be oriented towards IR photo-transistor L14F1 (T3). The IR music receiver uses popular op-amp IC µA741 and audio-frequency amplifier IC LM386 along with photo-transistor L14F1 and some discrete components (second diagram).

Receiver circuit diagram: 

 The melody generated by IC UM66 is transmitted through IR LEDs, received by phototransistor ceived by phototransistor T3 and fed to pin 2 of IC µA741 (IC2). Its gain can be varied using potmeter VR1. The output of IC µA741 is fed to IC LM386 (IC3) via capacitor C5 and potmeter VR2. The melody produced is heard through the receiver’s loudspeaker. Potmeter VR2 is used to control the volume of loudspeaker LS1 (8-ohm, 1W). Switching off the power supply stops melody generation. 

Author: Pardeep G, EFY Mag
Source http://www.extremecircuits.net/2010/05/ir-music-transmitter-and-reciever.html

09:53 0 comments