Diagram Plus guide

A DTMF-based IR transmitter and receiver pair can be used to realize a proximity detector. The circuit presented here enables you to detect any object capable of reflecting the IR beam and moving in front of the IR LED photo-detector pair up to a distance of about 12 cm from it. The circuit uses the commonly available telephony ICs such as dial-tone generator 91214B/91215B (IC1) and DTMF decoder CM8870 (IC2) in conjunction with infrared LED (IR LED1), photodiode D1, and other components as shown in the figure.

DTMF Proximity Detector Circuit Diagram

A properly regulated 5V DC power supply is required for operation of the circuit. The transmitter part is configured around dialer IC1. Its row 1 (pin 15) and column 1 (pin 12) get connected together via transistor T2 after a power-on delay (determined by capacitor C1 and resistors R1 and R16 in the base circuit of the transistor) to generate DTMF tone (combination of 697 Hz and 1209 Hz) corresponding to keypad digit “1” continuously. LED 2 is used to indicate the tone output from IC3.

This tone output is amplified by Darlington transistor pair of T3 and T4 to drive IR LED1 via variable resistor VR1 in series with fixed 10-ohm resistor R14. Thus IR LED1 produces tone-modulated IR light. Variable resistor VR1 controls the emission level to vary the transmission range. LED 3 indicates that transmission is taking place. A part of modulated IR light signal transmitted by IR LED1, after reflection from an object, falls on photodetector diode D1.

The photodetector is to be shielded from direct IR light transmission path of IR LED1 by using any opaque partition so that it receives only the reflected IR light.) On detection of the signal by photodetector, it is coupled to DTMF decoder IC2 through emitter-follower transistor T1. When the valid tone pair is detected by the decoder, its StD pin 15 (shorted to TOE pin 10) goes ‘high’. The detection of the object in proximity of IR transmitter-receiver combination is indicated by LED1.

The active-high logic output pulse (terminated at connector CON1, in the figure) can be used to switch on/off any device (such as a siren via a latch and relay driver) or it can be used to clock a counter, etc. This DTMF proximity detector finds applications in burglar alarms, object counter and tachometers, etc.

The material test of cell phone booster cannot be cancelled
Further established the worlds largest cell phone users status. Industrial scale, concentration increased as of April 2007, 41 new cell phone companies, including 11 foreign-invested enterprises, Chinese enterprises to 30, with production capacity of about 140 million while the new cell phone manufacturers in the low-end products based mainly on the Chinese market, the annual demand of about 60 million to 100 million units, made in China to exceed demand and production companies to expand the number of cell phone production growth will further exacerbate the market competition increasingly fierce competitive environment has led to an overall decline in industry profits, loss of business and the amount is increasing. cell phone booster can work continuously for a long time. On the other hand, the Chinese cell phone industry to further expand the industrial scale, while also further enhance the industrial concentration which Nokia, Motorola, Samsung, Sony Ericsson, Bird, Lenovo, and Amoi top ten companies account for almost the total production of all 80% of the industry, including Nokia, Motorola, Sony Ericsson and Samsung, the market share of 81.96 percent, the domestic cell phone market share of SMEs is very limited. 72. handset industry value chain structure of the cell phone industry value chain structure divided into three two components: the upper reaches of cell phone R & D, design and component suppliers, midstream and downstream cell phone handset manufacturers brand marketers, operators in the mobile industry on a technical level, Chinas cell phone industry is still in catch-up phase, the total production level in the cell phone Chinese cell phone industry in rapid growth stage. The company only takes responsibility of changing a new cell phone booster or repairing cell phone booster .
Chinese cell phone industry cluster is still in the global value chain under the low value-added chain. Handsets needed for the production of most of the active and passive, body parts (only about 30% of production costs) can be made, but not yet fully grasp the industry core technology and key components of the production technology, and small-scale enterprises, SMEs accounted for 92.61% of the proportion of overall competitiveness. Chinese cell phone industry structure shows structural characteristics of olive shape: the upper reaches of the lack of core technology and key components industry production technology; River is gradually assembled a strong, general parts production capacity; and downstream of brand management, logistics are still weak. Upstream: cell phone design platform (chip module). Overall, Chinas cell phone industry cluster is still in the low-value-added chain of production processes and generally supporting the production of parts gathering stage of development.