I have an assembled Bulbdial clock that works perfectly, however I need to add an alarm. Where should I connect it? I’m thinking of connecting pin 17-19, 9, or 10 (the ISP pins, or crystal pins[since I have a Chronodot]) to a transistor to power the alarm. Additionally, what sort of speaker should I use?
One thing to consider is how you’re going to reprogram the clock to take advantage of the speaker. If you’re going to use the USB-serial interface, then repurpose the ISP pins. If you’re going to use the ISP interface, repurpose the serial pins.
The crystal *is* used by the Bulbdial. So, if you want to run without it, you’ll need to reprogram the chip with an ISP interface (to set the fuses to run off of the internal timebase), and likely make other changes to the programming as well.
The Alpha Clock Five and Meggy Jr RGB kits use a little magnetic speaker/buzzer for their noises and alarms. It only requires one pin from the MCU (plus a transistor) to drive it. That type is likely a good choice. Use the contact form on our web store if you’d like to buy one from us.