POWER SOURCE OFF DELAY TIMER WITH LIQUID CRYSTAL DISPLAY

摘要

A power source off delay timer generates an off delay output after passage of a determinate time delay period from when an input power source is switched off. This timer includes a main body, a liquid crystal display mounted to the main body so as to display the operational condition of the timer, and a liquid crystal display drive unit for driving the liquid crystal display during the time that the power source is on and also during the determinate time delay period between the time instant at which the power source is switched off and the subsequent time instant at which the timer generates the off delay output. Thereby, the position of the liquid crystal display may be substantially arbitrarily selected, and also the position of the keep relay may be arbitrarily chosen. And because the liquid crystal display and also the drive unit therefore have typically very low power consumptions, it is possible to keep them in operation without exhausting the power source such as a capacitor for operating the timer after the power source has been switched off, even if the delay time period is very long. A variable resistor may be used for adjusting the time delay period; and the system may include a flasher circuit for flashing the liquid crystal display, to make its indication even more visible.