simple low cost digital code lock
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Digital Vom Phase Meter
The phase-angle meter operates with both analog and digital inputs. A digital voltmeter (DVM) serves as the readout device. The output is 1 mV per degree, with a full-scale output of 360 mV corresponding to 360 degrees. The MC1404 precision...
Microcontroller interfacing with RS 232
Standard serial interfacing of a microcontroller (TTL) with a PC or any RS232C standard device requires a TTL to RS232 level converter. A MAX232 is used for this purpose. It provides a 2-channel RS232C port and requires external 10µF capacitors.
The...
Keypad-Operated Switch No.2
This is a simplified version of the Universal Keypad-Operated Switch. The design has been modified to reduce circuit complexity and the number of components required. As a result, the code is somewhat less secure; however, it remains adequate for many...
delay
This article outlines the construction of a simple microcontroller-based delay circuit designed for photographic applications, such as drop or high-speed photography. It is capable of controlling the trigger lag for cameras and flash units, generating periodic trigger pulses, or managing...
Protecting Microcontroller Input Pins from Soft Power Switch
A soft power switch for a microcontroller is designed such that a momentary switch can activate the circuit, including the microcontroller. When the switch is pressed a second time, the microcontroller is capable of shutting itself down after executing necessary...
Security-door-ajar-alarm
The TL3019 device activates, or goes low, when a south pole of a magnet approaches the chip face. In this example, there are five doors, each equipped with a magnet embedded in its edge, with the south pole facing outward....
Power supplies for microcontroller based projects
This document discusses the use of small microcontrollers, such as those from the PIC and Atmel series, which typically operate at 5V and require less than 100mA for complete system functionality. Some PICs can function at lower voltages, such as...
Password electronic doorbell 1
The electronic doorbell circuit utilizes a password mechanism and includes both an electronic password circuit and a music generation circuit, as illustrated in Figure 3-118. The electronic password circuit is comprised of integrated circuit IC1, keys S1-S6, and diodes VD1-VD5....
Interactive Voice Response System
Nowadays every institution needs automation. As a part of college automation, a project has been developed for a Voice Interactive System for College Automation. This project allows users to quickly access student attendance and marks through the telephone line without...