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4 Digit Crystal-Controlled Timing Module

Just change the chip to build a stopwatch , a photographic timer, a frequency meter or a programmable down timer.

By Frank Crivelli & Peter Crowcroft

This simple little module measures just 61 x 67mm and is basically a start/stop timer. It's crystal-controlled to ensure accuracy, features an open-collector NPN output and sports a 4-digit LED display.

Currently, there are six timer firmware ICs available. You simply specify which one you want to build. The choices available to you are as follows:

(1) A Simple Photographic Timer (K148T1);

(2) A Stopwatch with Pause function (K148T2);

(3) A 40kHz Auto-Ranging Frequency Meter (K148T3);

(4) A Programmable Down Timer which counts down in minutes from a maximum of 10,000 minutes (K148T4);

(5) A Programmable Down Timer which counts down in hours from a maximum of 10,000 hours (K148T5); or

(6) A Programmable Down Timer which counts down in seconds from a maximum of 10,000 seconds (K148T0).

As supplied, the kit comes with option (6). If you want one of the other functions, the firmware (in the form of a different microcontroller IC) must be purchased separately. The documentation supplied with each option describes how it works.

Please note that, for this design, all source code is copyright and is not released with the firmware.

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