Rongge

Presettable times for train stops in stations are indispensable if you want to operate your model railway more or less realistically according to a timetable. This circuit shows how a 555 timer can be used with a relatively small timing capacitor to generate very long delay times as necessary by using a little trick (scarcely known among model railway electronic technicians): pulsed charging of the timing net-work. Such long delays can be used in hidden yards with through tracks, for instance.  As the timer is designed for half-wave operation, it requires only a single lead to the transformer and one to the switching track or reed contact when used with a Märklin AC system (H0 or H1). The other lead can be connected to any desired grounding point for the common ground of the track and lighting circuits. Circuit diagram : Long-Delay Stop Switch Circuit Diagram As seen from the outside, the timer acts as a monostable flip-flop. The output (pin 3) is low in the quiescent state. If a ...

Description A digital stop watch built around timer IC LM555 and 4-digit counter IC MM74C926  with multiplexed 7-segment LED display. MM74C926 consists of a 4-digit counter, an internal output latch, npn output sourcing drivers for common cathode, 7-segment display and an internal multiplexing circuitry with four multiplexing outputs. The counter advances on negative edge of the clock. The clock is generated by timer IC LM555. 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     Testing First, reset the circuit by pressing S3 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 S2. Rotary switch S1 is used to select the different time periods at the output of the astable multivibrator (IC1). Digital Timer Cir...