81: Let's Review

Apr 25, revised: May 2, Aug 1, Nov 18, 2015

Devices I've wired/programmed* for the Raspberry Pi, Arduino and Spark Core (now Particle Photon)

• LEDs (everyone starts with these) - RAS
• Push buttons - RA
• PIR motion detector - R
• Magnetic door sensor - RAS
• Photosensor RAS
• DS18B20 temperature sensor - RAS
• DHT22 temperature/humidity sensor - RAS
• TMP36 temperature sensor - AS
• Raspberry Pi camera (B/W conversion, timelapse, security cam) - R
• Relay Switches - RS
• Water (moisture) sensor - R
• Soil moisture sensor - AS
• Water valve/solenoid control - RS
• Rangefinder: ultrasonic, IR (several models) - RA
• Speakers - RA
• CO gas sensor - A
• Natural gas/propane sensor - A
• Mini vibrating motors - A
• Pi - Arduino Com over USB - A to R
• RF read & write - A
• RFID sensor - AS
• 16x2 LCD text device - RA
• 7-segment clock device - R

To make the above work--

• resistors, capacitors, diodes, transistors, 
• Darlington array - R 
• I2C (MPC2308) - RS 
• MPC3008 (analog) - R
• PWM - A
• Backup battery setup - RAS
• Also: Internet upload/download, email, text message - RS

* Programmed in Python, C, C++, Linux Shell, Crontab

(also posted at http://dicks-arduino-nano.blogspot.com/)

80: More on My UPS Battery Setup

I have tested the setup shown in post 79 (explained better in my Arduino blog post 11: dicks-arduino-nano-travails.blogspot.com).

First, I tried it with an Arduino Nano (most expendable). Worked.

Then, my Spark Core setup. Worked, too. I let the battery run down on this test. I'm not sure how long that took (+2 hours?) and I had not recharged the battery after trying it with the Nano. Then something nasty happened: the Powerboost 1000 sort of hiccuped off and on powering the Spark back on for a second each time. Good old Spark survived this but I wouldn't bet on a Pi doing as well. Also, the Powerboost was fried (Adafruit replaced it).

Finally, on a Raspberry Pi B (rev 2) with a fair number of GPIO pins connected including a WIFI dongle, a Pi-powered relay switch and a 7-segment clock display. I let it go nearly an hour then the Pi stopped running while the Powerboost still showed its green "powered" LED. Hummmm.

This is what I want for my Pi setups:

1. Detect fail (eg: by reading photosensor pointed at extern power light on Lipo charger).

2. Send out email and text msg warnings to humans (if internet-connected):
    "Power fail. Shutting DOWN! date/time".

3. In Linux: kill my running processes (especially anything writing files):
   % pgrep -u pi | sudo xargs kill -9 (for user "pi").

4. Linux: % sync; sync; sleep 5

5. Shut off 5v power from battery before voltage drops but so the system will restart when external power is restored.

Suggestions? Will the "Pi Juice" (see Kickstarter) do all of this?

79: I built a UPS (uninterruptible power supply/battery backup)

Under $35. Works with Raspberry Pi, Arduino, etc. I'm surprised UPS (reasonable price/size) isn't a hot topic in this (computer geek?) world.

Not difficult! Details at my Arduino blog, post 11--

http://dicks-arduino-nano.blogspot.com/