12: Device Review

Apr 25, revised: May 2, Aug 1, Nov 25, 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 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 (radio frequency) read & write - A to R
• 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

11: Uninterruptible Power (the other UPS) for Arduino, Spark Core or Raspberry Pi
* revised Apr 17, 2015 *

There seems to be precious little help on line for this even though it turned out to be pretty easy. I watched --

https://www.youtube.com/watch?v=RiZ0g1bJ8sw

I got my parts from Adafruit (charger: $6, powerboost: $15, 1200mAh battery: $10, plus their irritating shipping charges).

I tested this with an Arduino Nano--

both external power and  battery (note red LED*)

And with my Spark Core--

just battery

You can connect/disconnect the battery any time. And this will work for Raspberry Pi just as well (REVISED: probably, if the system doesn't draw more than 1000mA -- see dicks-raspberry-pi.blogspot.com/).

Also REVISED: When I let the Spark run until the battery ran down there was a problem: The Powerboost didn't just quit cleanly. The boost/Spark stopped/restarted, stopped/restarted (voltage hiccups?). I suppose that when the boost stopped drawing current then the battery recovered a bit. Anyway: not nice. The Powerboost has an Enable pin (labeled (EN). Grounding that will stop things cold. Then how does it restart? What un-grounds the EN? See * note below. Kudos to Spark that the Core survived undamaged! Note: the Powerboost did not survive (Adafruit replaced it).

Considering the way that (non-hobby) "programable controllers" are used, I'd think that a UPS setup like this would be about Arduino Lesson 3!

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* If you aimed a photo resistor ($1) at the charger's red LED external power indicator then you could detect power failure and shutdown gently (but HOW and HOW-TO-RESTART?).