Apakah rekan kerja berbicara terlalu lama pada pertemuan? Apakah Anda
menggunakan 'berbicara tongkat' tapi selalu ada satu orang yang tidak pernah memberikan itu? Apakah Anda ingin dapat meredam pols selama perdebatan ketika waktu yang diberikan adalah up?
Bleeping Bicara Timer adalah penghitung waktu mundur sederhana yang dibangun menggunakan logika analog yang memicu alarm piezo ketika waktunya tiba. Tidak ada Arduinos sini! Tidak ada logika digital yang terlibat. Hanya rangkaian sederhana yang dibangun dengan komponen umum yang melacak waktu. Rangkaian ini dibangun di sekitar terhormat IC timer 555, chip kecil yang terus mempesona saya dengan desain, rekayasa, dan aplikasi, dari theremins LDR untuk kontrol motor untuk mundur timer. Diperkirakan bahwa satu miliar 555s diproduksi setiap tahun.
Ubiquitous as it is, note that this project does not use the low-power CMOS 555 “TLC” variant. The LM555 variant from RadioShack is capable of 18V of maximum input voltage, and we’ll be plugging a 9V battery into this circuit. Low-power 555s are better suited for applications where prolonged battery life or finer precision are required.
Inside the 555 timer, from Charles Platt’s book Make: Electronics, p. 158.
Thus, to best explore and understand the operation of this circuit I highly recommend you breadboard it first. Because this is a countdown timer circuit that actual timing will vary based on components used. The minimum and maximum settings of the timer are partially controlled by the linear-taper potentiometer. Because we’re not using pin 1 of the pot, there is no “0” time coordinate. The connections from pin 2, the wiper, and pin 3, with this configuration, effectively made my timer range from ~35 seconds to 5 minutes. In my experiments I found there was a +/- margin of error of 3% (due to power dissipation from the electrolytic cap); this could add or subtract as much as 9 seconds to the timing when the pot is turned entirely to pin 3. Although truth be told the timer was more ‘precise’ the longer the time set, and it consistently hit 5:00 exactly.
So you’ll want to play with your components, take notes, and build accordingly. Here’s a snapshot of my breadboard layout:
I’ve color-coded the jumper connections, which I’ll go over in the project steps.
When the circuit is switched ON, the green LED will light up. When the countdown is complete, the green LED will switch off, the red LED will switch on, and the piezo buzzer will alarm! These two components will stay powered on until the circuit is switched OFF (or the battery dies). The piezo buzzer is loud, really loud. Annoyingly loud! 78dB loud :)
