Looking to use up some more of his flexible LED strip, Hackaday alum and Tindie writer [Jeremy Cook] tried for a funky accent to his dinner or coffee table: light up coasters.
Using his CNC router to carve out two pieces of translucent plastic to house four 3V CR2032 batteries, four pieces of LED strip, and some wire, [Cook] had created a pressure plate circuit that activated once a drink is set on it. The original layout of the circuit, however, didn’t work, and the space for the LED strips proved to be too small. A quick redesign and some more time with his router resulted in an almost working product. Initially intending to use screws to secure the coaster, hot glue provided the perfect amount of spring once he had thinned out the coaster top to allow it to more easily flex and complete the circuit.
[Jeremy] states that at present the coaster only lights up when the glass is closer to full, but suggests that this could be useful in restaurants to notify waiters at a glance when beverages are nearly empty. If you’re looking to build a coaster that tells you when your coffee or tea is at the perfect temperature, look no further.
[Thanks for the tip, Jeremy!]
I think I’d have ripped apart junk keyboard(s) for the rubber key domes for a light spring, not necessarily implementing that as the switch.
Maybe I’ve missed the point but I’d feel extremely self-conscious going somewhere where the hosts had drink coasters that did this. After one or two flashes my cup would be going onto the table next to the coaster, not on it. I’d like to sip my cup in peace, not have some thing that looks like it’s monitoring the guest’s drinking behaviour.
One Transistor to rule them all Two resistors to Meh!!
Simple on is off using a transistor
That smacks of paranoia or judgemental friends.
The mass sensitivity is a cool byproduct, once it stops lighting up it’s time for the host to refill :)
Haha, exactly!
Or the use of a QTC pill.
How to replace battery?
Ha, good question! The hot glue is easy to remove and replace. Not very elegant, but seems like it would work. I’d guess these LEDs will run a long time on 4 batteries though, judging how long “throwies” can stay on.
Thanks for the writeup James!
It would be more interesting it it starts to blink to let the bartender that you want a refill or, if you turn it over showing red it means that you had enough. It also could use wireless and 6 axes sensor to enhance the options (like choosing a new drink from the screen above the bar).
Or simply if you tap it it will scream: “garson, encore une fois”.