I ordered boards to test a new power supply design. It’s based around the National Semiconductor LM2576. This accepts 7v to 40v as input and uses switching to produce a stable 5v output.
One of the things that became apparent to me as I worked on TinyTimer and TinyPLC is that a USB power input wasn’t always convenient. I still think it is a great power source for small electronics. The wall transformers are plentiful, cheap, and have a very easy to find cable that is very durable. All qualities that are optimal for small embedded projects.
However, in some control applications it would be convenient to use whatever DC power is handy. A rectifier could be added in some cases to deal with AC sources like 24vac which is very common.
I am also looking at the LNK306PN which is essentially a power supply on a chip.
Here is an image of the prototype / testing board:
I wrapped up the code for TinyTimer KickStarter edition. This completes the project and paves the way for units to ship. It has several unique features that are missing from similar units on the market. These features include:
Arduino IDE compatible for education and hacking
OpenSource Hardware design with Eagle files available.
Push Button programming and easy to use jumper for run/program mode.
Natively supports time periods of deciseconds (1/10th second), seconds, minutes, hours, and days.
Allows periods to be mixed for significant flexibility.
Supports values of up to 9999 for deciseconds, seconds, minutes, and hours. Days are limited to 490 based on limitations in 32 bit unsigned long numbers.
Run a pump for 1 hour per day, or per week.
Flash a light for 2.5 seconds once per minute.
Run a device for 2 hours once per 30 days.
Kit price is expected to be $55 with a fully assembled and tested unit for $75. Shipping not included.