Mutchus

This circuit was designed to block signals from infrared remote controls. This will prove very useful if your children have the tendency to switch channels all the time. It is also effective when your children aren’t permitted to watch TV as a punishment. Putting the TV on standby and put-ting the remote control out of action can be enough in this case. Circuit diagram : Remote Control Blocker Circuit Diagram The way in which we do this is very straightforward. Two IR LEDs continuously transmit infrared light with a frequency that can be set between 32 and 41 kHz. Most remote controls work at a frequency of 36 kHz or 38 kHz. The disruption of the remote control occurs as follows. The ‘automatic gain’ of the IR receiver in TVs, CD players, home cinema systems, etc. reduces the gain of the receiver due to the strong signal from the IR LEDs. Any IR signals from a remote control are then too weak to be detected by the receiver. Hence the equipment no longer ‘sees’ the remote control!...

It is often the case these days that the washing machine and  tumble dryer are installed in an outbuilding  or corner of a garage. This not only makes the kitchen a much quieter place but also leaves room for a dish washer and gives additional cupboard space. The problem now is how to tell when the wash cycle is finished. In bad weather you don’t want to make too many fruitless trips down the garden path just to check if the wash cycle is finished. The author was faced with this problem when he remembered a spare wireless door chime he had. With a few additional components and a phototransistor to passively detect when the washing machine’s ‘end’ LED comes on, the problem was solved. Circuit diagram : Remote Washing Machine Alert Circuit Diagram C1 smoothes out any fluctuations in the LED light output (they are often driven by a multiplex signal) producing a more stable DC voltage to inputs 2 and 6 of IC1. The circuit is battery powered so the CMOS version of the familiar 555 time...

The circuit diagram shown in Fig.1 uses a PNA4602M IR detector to receive an IR signal from  the remote control. It’s a neat device, which contains an IR receiver, amplifier and demodulator together in a single 3-pin package, and it’s normally used in circuits where you want to decode an IR remote control signal.   The way the circuit (Fig.1) works is as follows. When there is no IR coded signal present, the output pin of IC1 remains high. This high signal is fed to the trigger input of the 555 timer (IC2), which being configured as a monostable timer, prevents the timer operating.   Whenever you briefly press any key on the old remote control its IR signal is received by IC1 and output pin 1 produces a train of fast moving high and low pulses, which mimic the IR signal code sent by the remote control. We are not interested in this code, but as soon as the signal switches low it triggers the monostable timer IC2 and its output pin 3 goes high for a short period of time, s...

HART (Highway Addressable Remote Transducer) The very known 4-20 mA signal is a tried, tested and widely used standard for transmitting sensor data to the Control system. However only limited amount of information is sent by a 4-20 mA signal. HART (Highway Addressable Remote Transducer) protocol enhances these operations by transmitting digital data along with the 4-20 ma signal – without disturbing the signal. HART also permits two-way communications. It also has a digital modes that allows instrument to be connected to a single cable, cutting installation costs drastically. HART makes use of the Bell 202 frequency shift keying (FSK) standard to superimpose low-level digital signals on the 4-20 mA circuit enabling more information than just the process variable to communicate between transmitters and receivers.   HART and The Conventional Process Loop HART is best understood by looking at how it evolved from a conventional process loop. Figure  is a simplified diagram of the...

This circuit will allow you to turn on any piece of equipment that operates on 115 volts ac. The receiver circuit is based on the Radio Shack infrared receiver module (MOD), part number 276-137. It is also available from some of the other sources listed on my s page. The MOD accepts a 40khz IR signal that is modulated at 4 khz. Circuit Diagram When a signal is received the MOD will go low. The sensitivity of the MOD is set by different values for R1 and C1. The values for R1 may need to be as high as 10,000 ohms and for C1 40uf. This will prevent the unit from turning on under normal lighting conditions. You will need to experiment with the values that work best for you. The output of the 4013 chip a flip flop toggles on and off with the reception of a IR pulse. The output of the 4013 turns on the MOC optical coupler which in turn switches on the triac and supplies power to the AC load.

Remote Field Strength Meter Circuit Diagram. This field strength meter consists of a tuned crystal detector producing a dc output voltage from a transmitted signal. The dc voltage is used to shift the frequency of a transmitter of 100-mW power operating at 1650 kHz. The frequency shift is proportional to the received field strength. This unit has a range of several hundred feet and is operated under FCC part 15 rules (100-mW max power into a 2-m-iong antenna between 510 and 1705 kHz). Remote Field Strength Meter Circuit Diagram

The receiver is intended primarily for use with the remote control UHF transmitter described in the preceding article. It is a super-regenerative type with an active RF amplifier, T1. The antenna signal is applied to the input inductor via a BNC socket, K1. The input circuit is tuned by trimmer C4. The amplified RF signal is applied to the input of the super-regenerative stage based on transistor T2. Although  the oscillator is, strictly speaking, not tuned, it will lock on to the amplified RF signal applied via coupling capacitor C7. The low-frequency modulation component is extracted from the oscillator signal with the aid of low-pass filter, R6-R7-C12-R8-C13. The signal level at the demodulator output is 50 to 800 mVpp, so that further amplification is required·before the signal can be applied to a digital input.   The inductors in the RF amplifier input and output are made from 1 mm dia. silver-plated wire. The length of the pieces of wire is indicated by the component...

Where would we be without our infrared remote controls? Stuck back in the dinosaur era, that's where. IR remote controls are now built into lots of appliances, ranging from TV sets and VCRs to audio equipment, robots and lights. This relatively simple design makes it easy for you to add infrared remote control to your latest project or to existing equipment. What's more, it can control up to 10 different functions, which should be more than enough for most applications (usually, you'll only need one or two channels). Each output uses an open-collector transistor and this can be used to switch a relay or even to directly switch other 12V equipment. The outputs can also be used to drive LEDs via current limiting resistors or to drive optocouplers (eg, to provide isolation from high-voltage circuitry). Heavy current items such as motors and light bulbs will have to be driven by relays. We've made the job easy for you by including diagrams that show all the various options ...