Showing posts with label INFRARED. Show all posts
Showing posts with label INFRARED. Show all posts
Tuesday, July 12, 2011
CONTROL RELAY WITH INFRARED CIRCUIT SCHEMATIC DIAGRAM
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 (IR LED1) and the phototransistor (T1).
The infrared rays transmitted by IR LED1 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, IRLED1, phototransistor and other discrete components. When regu lated 5V is connected to the circuit, IR LED1 emits infrared rays, which are received by phototransistor T1 if it is properly aligned. The collector of T1 is connected to non-inverting pin 3 of IC1. Inverting pin 2 of IC1 is connected to voltage-divider preset VR1. Using preset VR1 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 (T2). The high output of IC1 at pin 6 drives transistor T2 to energise relay RL1 and switch on the appliance, say, hand dryer, through the relay contacts. The working of the circuit is simple.
Sunday, June 12, 2011
IR Remote Control Circuit using Op amp 741
IR circuit is called Infrared Circuit. Remote controls are very much popular now-a-days. It is specially called cordless circuit. This circuit is very simple and low cost cordless remote control circuit which is based on infrared rays.
Figure 1 shows the transmitter circuit. The transmitter produces infrared rays and that can be easily transmitted up to 4 meters with a special convex lens and a twin LED arrangements.
Figure 2 shows the receiver circuit. Op amp IC1-741 generates high frequency squire wave which provides the gate pulses for SCR1. IC1’s output current flows through SRC1 and it is conducting current and enables the LED to emits infrared rays. The output frequency of Op amp IC1 depends on the variable resistor VR1, which in turns varies the output radiations of the LED.
When IR rays fall on the photo-transistor T1 of the receiver, then base of the photo-transistor’s base produces charge carriers at a rate depending on the rate of arrival of incident radiations at the pn junction of the transistor. Then the resulting emitter voltage is amplified by Op amp IC-2 . The amplified signal is rectified by D2. Finally the amplified signal is to drive the relay.
Parts List:
Tuesday, February 15, 2011
Simple Remote Control Circuit
This Infrared Remote Control Software project based on Microchip 16C57 microcontroller is a reference guide to decode infrared remote control signals fromtelevision, VCR, air conditioner or other home appliances handset that uses NEC 6121 infrared format. Once one is ableto understand how to decode an IR signal of a certain format, decoding another format can be easily done as the flow chartis more or less the same except the timing of the new format.
The NEC 6121 format is based on pulse width timing in determining whether the data transmitted is "1" or "0". The data "1" is determined by the pulse width timing from one risingedge to the next rising edge of 2.24ms. The data "0" is determined by the pulse width timing from one rising edge to thenext rising edge of 1.12ms.
Most of the transmitter are modulated using a frequency of 32.75 kHz, 35.0 kHz, 36.0 kHz, 36.7 kHz, 38 kHz, 39 kHz, 40 kHz, 41.7 kHz, 48 kHz, and 56.8 kHz. The ones that are commonly used are 38 kHz and 40 kHz. In order to decode the received signals, the corresponding demodulating receiver must be used. For instance, if a modulating frequency at the transmitterused is 40 kHz, then the receiver demodulating frequency used should be 40 kHz as well. Modulating the data is a betterdesign as this will make the data integrity better and less susceptible to noise. The demodulating receivers can be obtainedfrom suppliers such as Vishay, LiteOn, Sharp or Kodenshi.
One word of caution when using the IR remote control is that it is easily affected by lighting devices that emits the infrared frequency. One such example is the fluorescent tube which emits the infrared frequency in its operation. When thistype of lights is operating, the receiver may not be able to receive the signal from the transmtter due to interference fromthe signals emitted by the flurescent tube. In situation like this, confirm this by switching off the lights when controlling the device.
You may want to consider using RF frequency as a solution in this particular location. Another way isto place a filter in front of the receiver to narrow the infrared window but this solution will compromise the angle andoperating distance of the infrared transmitter.
The infrared remote control software project provides the flow chart and source code and can be downloaded from Microchip website.
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