Hiya folks,
I was looking for an intervalometer for my camera. The cheapest decent model is $35 on amazon, and is kind of crummy.
The remote control for my camera is insanely simple: a 2.5mm jack has three connections - base, middle, and tip - and one simply shorts middle to base to focus, and tip to base to take a picture. For those of you who don't do electric stuff, here's how easy that is: If you plug the wire into the camera, and lick the other end of the wire, it will take a picture because your tongue will complete the circuit. (Tiny voltage and almost zero current means you won't feel it! But disclaimer, don't do it because you read it here.)
For $35, I am able to:
1. Most importantly: replicate the functions of the $35 device; no point creating something worse
2. Order circuit boards - $15 from seeedstudio fusion for 10x boards (super cheap!)
3. Add a fancier microcontroller than required ($3) so I can program new modes that don't exist to suit my needs over the years
4. Make a user interface allowing more options
5. Add USB charging
6. Add USB communication with any computer device (including phones, little boards like the ras pi, etc), as well as serial communication (for other microcontrollers)
7. Add the ability to let other sources control the camera through the board - for example, my phone, or a wireless controller - and let the boards be daisy-chained to control multiple cameras at once
8. Practice circuit design and board layout!
There are a lot of consumer devices that are just disgustingly simple. Some other examples include battery chargers ($1 circuit board, $0.50 - $2 battery holder, $1 usb connection, $1 charger chip with appropriate resistors, capacitors, indicator LED, etc), power adapters (12V car output to 5V USB; 9V battery to 5V USB... anything to USB is easy; though I might pay the $5 for a 120VAC to 5V USB to avoid the headache), and so on. You can often drastically improve the product; I'd rather have one common power supply board instead of eight different converters. It's a lot of fun to build these things, often for half the cost, and exercise your head-meat muscles! Of course, it has to be fun, otherwise you're spending 10 hours to save $10 and add some functions.
Sometimes you find a consumer device that actually makes sense to build from scratch even if it's not your idea of a relaxing after-work activity. For example, I'm looking at making a signal generator for some specific stuff; this would cost $25 instead of $300 or more. The best part about doing this is that you might get a business opportunity out of it.