Pre amplifier
SIMPLE ELECTRONIC LOCK PROJECT
TRAFFIC SIGNALING
CONSTRUCT A UNIPOLAR STEPPER MOTOR CONTROL DRIVER
BUILD A PROGRAM REMOTE CONTROL IR TRANSMITTER USING HT6221/HT6222 IC
GATE ALARAM NETWORK
WEATHER STATION

PRE AMPLIFIER

This preamp is very simple, and will work under tough conditions. The input impedance is pretty high, so it won't load down electric guitars. It will also amplify microphones. When I have a moment, I'll make some additions that will optimize it for microphones, and also show how to power a condenser microphone.
The power source is typically a 9-volt battery, but the circuit will tolerate 6 to 30 volts. Battery drain at idle is about 1 milliamp. The two red LEDs are important in the circuit - they act as a voltage reference to set the operating point of the opamp.

The output will tolerate a fair amount of abuse, and you can plug headphones into it in a pinch.

Please note that I have shown a generic symbol for a jack both at the input and output. Use whatever you need, or none at all.

Simple Electronic Lock Project

ones at the same time, but not press any of the cancel switches. Pressing just one cancel switch will prevent the circuit unlocking. When the circuit unlocks it actually just turns on an LED for about one second, but it is intended to be adapted to turn on a relay which could be used to switch on another circuit.

Please Note: This circuit just turns on an LED for about one second when the correct switches are pressed. It does not actually lock or unlock anything!

This project uses a 555 monostable circuit.

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Parts Required
resistors: 470, 100k ×2, 1M
capacitors: 0.1µF, 1µF 16V radial
red LED
555 timer IC
8-pin DIL socket for IC
on/off switch
push-switch ×6 (or more)
battery clip for 9V PP3
stripboard 12 rows × 25 holes

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strip board layout





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circuit diagram



There are six (or more) push switches. To 'unlock' you must press all the correct

TRAFFIC SIGNALING

This project operates red, amber and green LEDs in the correct sequence for a single UK traffic light. The time taken for the complete red - red & amber - green - amber sequence can be varied from about 7s to about 2½ minutes by adjusting the 1M preset. Some amber LEDs emit light that is almost red so you may prefer to use a yellow LED.

The 555 astable circuit provides clock pulses for the 4017 counter which has ten outputs (Q0 to Q9). Each output becomes high in turn as the clock pulses are received. Appropriate outputs are combined with diodes to supply the amber and green LEDs. The red LED is connected to the ÷10 output which is high for the first 5 counts (Q0-Q4 high), this saves using 5 diodes for red and simplifies the circuit.


This project uses a 555 astable circuit to provide the clock pulses for the 4017 counter.


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Parts Required:
resistors: 470 ×3, 22k, 100k
capacitors: 0.1µF, 1µF 16V radial, 10µF 16V radial
diodes: 1N4148 ×6
LEDs: red, amber (or yellow), green
1M preset, horizontal
555 timer IC, such as NE555
4017 counter IC
DIL sockets for ICs: 8-pin, 16-pin
on/off switch
battery clip for 9V PP3
stripboard: 20 rows × 21 holes
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stripboard diagram

circuit diagram

Construct a Unipolar Stepper Motor Control Driver

click here to see how to construct a stepper motor

Build A Program Remote Control IR Transmitter Using HT6221/HT6222 IC

Program Remote Control IR Transmitter

This project is based on integrated circuit from Holtek Semiconductor HT6221/HT6222. Similar parts used to be produced by NEC Semiconductor uPD6121/uPD6122. These ICs are commonly used in television and VCR infra red remote controls, garage door controllers, car door controllers, security systems and other remote control applications.

They are capable of encoding 16-bit address codes and 8-bit data codes. Each address/data input can be set to one of the two logic states, 0 and 1. The HT6221 can have keys up to 32(K1~K32) and HT6222 64 keys (K1~K64). When one of the keys is triggered, the programmed address/data is transmitted together with the header bits via an IR (38kHz carrier) transmission medium.

This project provides the transmitter part of the remote control. Designers and hobbyists will have to do their own software at the receiver board. Those who are familiar with microcontroller programming will find this device easy to use. The features of this IC are:

Operating voltage: 1.8V to 3.5V DC
Data output with 38kHz carrier for IR medium
Low standby current
455kHz ceramic resonator or crystal
16-bit address codes
8-bit data codes
Pulse Position Modulation code method

Program Remote Control Circuit Description


Program Remote Control Circuit Description
The typical 32 pins HT6221 schematic is as shown above. However, the values of 1k ohm and 47 ohm at the output pin 5 of the IC can be reduced to increase the distance the IR signal is transmitted. After the transmission codes are sent, the DOUT pin generates transmission codes with a carrier, and the LED goes low to drive a transmission indicator.

When one of the keys is triggered for over 36ms, the oscillator is enabled and the chip is activated. If the key is pressed and held for 108ms or less, the 108ms transmission codes are enabled and comprised of a header code (9ms), an off code (4.5ms), low byte address codes (9ms-18ms), high byte address codes (9ms-18ms), 8-bit data codes (9ms-18ms), and the inverse codes of the 8-bit data codes (9ms-18ms).

After the pressed key is held for 108ms, if the key is still held down, the transmission codes turn out to be a composition of header (9ms) and off codes (2.5ms) only.

Logic 0 is represented by timing 1.12ms and logic 1 by timing 2.24ms using pulse position modulation method as shown below.



The address code and data codes are set using the diodes 1N4148 and resistors 51K ohm and whether D7 is connected to Vcc or Ground.

Gate Alaram Network

Description:A cheap and simple gate alarm made from a single CMOS Integrated Circuit.
Circuit Notes
Figure 1 represents a cheap and simple Gate Alarm, that is intended to run off a small universal AC-DC power supply.
IC1a is a fast oscillator, and IC1b a slow oscillator, which are combined through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, etc.) is opened. The circuit is intended not so much to sound like a siren or warning device, but rather to give the impression: "You have been noticed." R1 and D1 may be omitted, and the value of R2 perhaps reduced, to make the Gate Alarm sound more like a warning device. VR1 adjusts the frequency of the sound emitted.
IC1d is a timer which causes the Gate Alarm to emit some 20 to 30 further pips after the gate has been closed again, before it falls silent, as if to say: "I'm more clever than a simple on-off device." Piezo disk S1 may be replaced with a LED if desired, the LED being wired in series with a 1K resistor.
Figure 2 shows how an ordinary reed switch may be converted to close (a "normally closed" switch) when the gate is opened. A continuity tester makes the work easy. Note that many reed switches are delicate, and therefore wires which are soldered to the reed switch should not be flexed at all near the switch. Other types of switches, such as microswitches, may also be used.

Weather station

This link contains project about whether station

http://www.techdesign.be/projects/012/012.htm