Electronics circuits | Elektronik Devreler - Projeler Ödevler - Tez Ödevleri

IR Remote Control

Ferhat Çelik — Wed, 09 Apr 2014 22:32:53 +0000

The post IR Remote Control first appeared on Elektronik Devreler - Projeler Ödevler - Tez Ödevleri.

DIGITAL STOP WATCH

Ferhat Çelik — Wed, 09 Apr 2014 22:26:46 +0000

Here’s a digital stop watch built
around timer IC LM555 and 4-digit
counter IC with multiplexed 7-segment
output drivers (MM74C926).
IC MM74C926 consists of a 4-digit
counter, an internal output latch, npn
output sourcing drivers for commoncathode,
7-segment display and an
internal multiplexing circuitry with four
multiplexing outputs. The multiplexing circuit
has its own free running oscillator,
and requires no external clock. The
counter advances on negative edge of
the clock. The clock is generated by timer
IC LM555 (IC1) and applied to pin 12
of IC2.
A high signal on reset pin 13 of
IC2 resets the counter to zero. Reset pin
13 is connected to +5V through reset
C.H. VITHALANI push-on-switch S3. When S2 is momentarily
pressed, the count value becomes
0, transistor T1 conducts and it resets
IC1. Counting starts when S2 is in ‘off’
condition.
A low signal on the latch-enable input
pin 5 (LE) of IC2 latches the number in
the counter into the internal output latches.
When switch S2 is pressed, pin 5 goes
low and hence the count value gets stored
in the latch. Display-select pin 6 (DS) decides
whether the number on the counter
or the number stored in the latch is to be
displayed. If pin 6 is low the number in
the output latch is displayed, and if pin 6
is high the number in the counter is displayed.
When switch S2 is pressed, the
base of pnp transistor T2 is connected to
ground and it starts conducting. The emitter
of T2 is connected to DS pin of IC2.
Thus, when switch S3 is pressed, reset
pin 13 of IC2 is connected to ground
via transistor T1 and the oscillator does
not generate clock pulses. This is done
to achieve synchronisation between IC1
and IC2.
First, reset the circuit so that the display
shows ‘0000.’ Now open switch S2
for the stop watch to start counting the
time. If you want to stop the clock, close
switch S2.
Rotary switch S1 is used to select the
different time periods at the output of the
astable multivibrator (IC1). The circuit
works off a 5V power supply. It can be
easily assembled on a general-purpose
PCB. Enclose the circuit in a metal box
with provisions for four 7-segment displays,
rotary switch S1, start/stop switch
S2 and reset switch S3 in the front panel
of the box.

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Fridge Door Alarm Circuit

Ferhat Çelik — Tue, 21 Jan 2014 21:17:57 +0000

This fridge door alarm is using a 3V battery supply should be placed (in a small box) in the fridge near the lamp or close to the opening. With the door closed the photo resistor R2 presents a high resistance (>200K) thus clamping IC1 by holding C1 fully charged across R1 and D1.

When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance (<2K) stopping C1 charging current. Therefore IC1, wired as an astable multivibrator, starts oscillating at a very low frequency and after a period of about 24 sec. its output pin (#3) goes high, enabling IC2.

This chip is also wired as an astable multivibrator, driving the Piezo sounder intermittently at about 5 times per second. The alarm is activated for about 17 sec. then stopped for the same time period and the cycle repeats until the fridge door closes.
Some notes for the fridge door alarm:

Delay time can be varied changing C1 and/or R3 values.
Beeper repetition rate can be varied changing C2 and/or R4 values.
Stand-by current drawing: 150µA.
Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture.
Do not put this device in the freezer.

Fridge door alarm circuit diagram

Components Values
R1 = 10K 1/4W Resistor
R2 = Photoresistor (any type)
R3 = 2M2 1/4W Resistor
R4 = 1M 1/4W Resistor
C1= 10µF 25V Electrolytic Capacitor
C2 = 100nF 63V Polyester Capacitor
D1 = 1N4148 75V 150mA Diode
IC1, IC2 = 7555 or TS555CN CMos Timer ICs
BZ1 = Piezo sounder (incorporating 3KHz oscillator)
B1 = 3V Battery (2 x 1.5V AA, AAA or smaller type Cells in series)

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Infrared Beam Break Detector

Ferhat Çelik — Tue, 21 Jan 2014 21:14:02 +0000

Application

An infrared detector that sounds a buzzer when an IR beam is broken, meaning the IR signal is lost. A pulsed IR signal generator is necessary, but not included in this post. This project would be ideal for doorways or hallways to alert when someone enters or exits an area.

Description

The IR sensor responds to pulsed infrared, not ambient or continuous IR. This means that another transmitter project is necessary in order to complete this one! Note though that some forms of lighting like fluorescent lighting may interfere with the sensor. For convenience, the the buzzer is internally driven so that a only Vdc is needed to make a sound. In this case, the IR sensor senses 38kHz pulsed infrared light.

Pin 3 of the IR sensor is actually low (0V) while receiving a signal. When the sensor is blocked from receiving the IR signal, the sensor outputs a high signal to the comparator, which then allows current through the LED/Buzzer circuit, and alerting you that the beam is broken. In the Scheme-It drawing the LM311 IC is a grouping of three components, in a functional block diagram style, to show how it functions in the circuit beyond what the pinouts would show normally.

Schematic of the IR Beam Detector Circuit

Parts list

RefDes	Name	Value	Part Number	Digi-Key Part	Description
U1	IR SENSOR		GP1UX511QS	425-2501-ND	RECEIVER IR REM CTRL 5V 38KHZ
R1	RESISTOR	22K	ERJ-8GEYJ223V	P22KECT-ND	RES 22K OHM 1/4W 5% 1206 SMD
R2	RESISTOR	1K	ERJ-8GEYJ102V	P1.0KECT-ND	RES 1K OHM 1/4W 5% 1206 SMD
C1	POLARIZED	10uF	293D106X0025C2TE3	718-1044-1-ND	CAP TANT 10UF 25V 20% 2312
U2	OPAMP	LM311	LM311DR	296-1388-1-ND	IC DIFF COMP STROBE 8-SOIC
R3	RESISTOR	1K	ERJ-8GEYJ102V	P1.0KECT-ND	RES 1K OHM 1/4W 5% 1206 SMD
L1	LED		TLHK5800	751-1119-ND	LED 5MM RED 5500MCD ALINGAP GAAS
SPK1	SPEAKER	Buzzer	CT-1205CL-SMT	102-1267-1-ND	BUZZER AUDIO MAGNETIC 5VDC SMD

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