ffd

As already stated, the design features a 4-digit 7-segment LED display (with decimal points) plus an open-collector output. Depending on your application, this output can be used to operate a relay or sound a buzzer at the end of the timing period. In addition, there are three inputs to the circuit: Reset, Start & Stop. The Reset input is a hardware reset to the microcontroller, while the Start & Stop input functions vary according to the firmware used. All inputs are normally pulled high and may be pulled low by switches or relays, or by an open collector output (ie, when the transistor turns on). Two on-board pushbutton switches are also connected across the Start & Stop inputs. These enable you to test the basic operation of the timer module without hooking up external hardware (apart from a power supply). Basically, they are there to help you get the unit "up and running". To make the module easy to use, all the inputs and outputs are brought out to a single 1...

This code lock is useful for appliances requiring exclusive or authorised use by those who know the preset code. If desired, the code can be changed. The circuit doesn’t require additional AND or NOT gate operations at the outputs. It uses two pairs of 4-way DIP switches. The code is set using DIP switches DIP3 and DIP4. Then these two switches are hidden inside the assembly. With DIP3 and DIP4, up to 256 code combinations are possible. The unlocking code is set by the user using DIP switches DIP1 and DIP2, which is compared with the preset code entered earlier via DIP3 and DIP4. If the two codes match, transistor T1 conducts. 8-Digit Code Lock for Appliance Switching Circuit Diagram   The codes are compared using two cascaded 4-bit magnitude comparator Ics (IC1 and IC2). If the input nibble present at DIP1 matches with preset DIP3 nibble, output pin 6 of IC1 (connected to input pin 3 of IC2) goes high. Now if nibble present at DIP2 matches with the preset nibble at DIP4, pin 6 of ...