Blog

May 22, 2015 | Electronics |

A Silly Birthday Greeting Box



There seems to be a deluge of cheap toys in my house, thanks to the kids. But on the upside, many of these have interesting electronics that are perfect for little hacks. I wanted to make a quick birthday gift for my wife, and I remembered that I had stashed away this particularly annoying toy (a cycle bell?) that sang “Happy Birthday” continuously in an ear-shattering tone. So I decided to make a birthday greeting box out of it. Here’s what the ear-shatterer looks like, outside and inside.



Toy

So it consists of a “black box” IC, which is connected to a push button and a 3V battery box, and has outputs for a speaker and an LED. After making a little sketch of the connection, I desoldered all the wires, and cut off the hot glue to extract the speaker. The wires were really flimsy and the soldering, connections etc. were clearly done by an “I hate my job and want to shoot my boss” kind of employee.

For the box, I used the unused case for my wrist watch (also unused). I wanted the music to be triggered when the box is opened. I’ve done something similar before that earned me my “5 minutes of fame” on hackaday and lifehacker. So I decide to take the same approach here - use a MOSFET and a reed switch. The scheme is shown below.



Circuit

The high resistence (1 Mega Ohm) ensures that the current drain when the box is closed in really small - which means more battery life. When the box is closed, the reed switch is closed, the gate of the MOSFET is grounded, and it doesn’t supply power to the circuit. When the box is opened, the reed switch opens, and the MOSFET turns on, supplying power to the screamer. By design, the push button triggers the music on for each press. But since I want an on/off type of system, I just shorted the push-button connection, and connected the circuit’s power supply across VCC and the drain of the MOSFET. The magnet, fixed to the top flap of the box, was stolen from the kitchen refrigerator. (I can’t resist magnets, so I keep buying this junk at every international airport I pass through.) I also replaced the red LED with a cooler blue LED.



Box

Now for some personality. My son helped me find three LEGO figures to represent our team - construction worker, pirate (?) and Obi-Wan. Pirate is holding the blue LED, which flickers in sync with the screeching. And the box had the perfect slot for a Greeting card. Here is the completed masterpiece (you can see it in action at the YouTube link on top of the page):



Box Final

I am never throwing broken toys away. ;-)


Consulting

Need help with a hardware project or product? Drop us an email at info@electronut.in. We offer consulting services on AVR and Nordic nRF BLE - hardware design, firmware development, prototyping, PCB design/assembly, sourcing and manufacturing. We can help you bring your product to market!


Bluey nRF52 BLE IoT dev board

bluey
Check out our Bluey nRF52 BLE development board with built-in Accelerometer/Gyroscope, Temperature/Humidity and Ambient Light sensors. It's a fabulous tool to learn Nordic nRF52 BLE programming and explore IoT technologies.

Questions/Comments

We love hearing from our readers. Email us at info@electronut.in for questions or comments on this article. If you found this article useful, please support us by buying some of our hardware products.


Please sign up for updates

Once in a while, we will send you an email update on the latest Electronut Labs projects and products. Your email address will never be shared or abused, ever.

2016 Electronut Labs. All rights reserved.