Which micro controller would be suitable? (camera/wifi/PIR sensor)

Discussion in 'Embedded Systems and Microcontrollers' started by mastermaw, Apr 25, 2013.

  1. mastermaw

    Thread Starter New Member

    Apr 25, 2013
    Hello all, I need some recommendations for microcontrollers. The project is a small security device, running on a single AA or button cell.

    A PIR sensor detects motion, which latches a relay, turning on a camera and WiFi.

    The camera takes a picture, saves it to storage and then emails the picture via SMTP to a preset recipient and deletes the image.

    Of course to conserve power the cam and wifi are always turned off unless motion is detected. Clearly a small button cell wouldn't last long powering wifi!
    So, I need a microcontroller with very low consumption, at least 1mb of onboard storage, a CPU capable of processing an image and firing off an email within 10 seconds, and reasonably simple connectivity with a WiFi chip and camera.

    Ideally, all the components should ultimately be available for under $40 - but for my project, it's not an issue. The components should also ideally fit in a 5cm2 box - but for a prototype, size isn't a problem.

    I know similar security devices exist but this is a fun project for me. The crucial thing here is that the device can run on a small battery - AA or perhaps a button cell. In which case, might it be sensible to have the PIR+controller separate to the cam/wifi controller?

    Does a suitable microcontroller spring to mind? I've played with arduinos but find the various shields a little clumsy and thought better options might exist. There are so many Atmel and TI options out there, it's a bit bewildering.

    Any advice much appreciated!

  2. Litch


    Jan 25, 2013
    You're over complicating this.

    Does it really have to run on a AA or 3V button? This is a major limitation, if you can get mains power (or a 5v supply from a plugpack) it would seriously simplify the project by opening up a lot more uC options.

    I would *try* and suggest a PIC32 series uC; a USB web cam and a USB WiFi dongle that you'll somehow have to reverse-engineer both to get working on a PIC32.

    If you had a constant power source, I'd suggest a Rasberry Pi or Beagle Bone - both run linux, and thus have ample support for web cams, wifi dongles and rich SMTP capabilities.

    A RPi sucks about 3-5 Watts; if you must use a batter - a car battery will last a week (and will require recharging); you'll need to use a DC-DC converter as a VREG will dissipate too much power.
  3. mastermaw

    Thread Starter New Member

    Apr 25, 2013
    Thanks so much for getting back to me.

    I'm afraid it does have to be battery powered. The point of this project is absolute portability. The final product would be wrapped in design similar to the Lytro camera, and could be left anywhere.

    Because of that, RPi or Beagle are out of the question.

    Thanks for the PIC32 suggestion though. I've just found this demo board that looks interesting:


    And the pinoccio (http://igg.me/p/303586) might work - although the ability to process an image and send an email+attachment in a sensible timeframe might be a struggle.

    For me, half the problem with security cams is the awkward need to wire the bastards up. My little project does away with that - trouble is, it's not looking too feasible, particularly as I'm a coder, not a hardware dev!

    Thanks again.

  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Battery power should not be a huge issue. Just turn off devices you're not using when not being used: this includes the processor, which should be sleeping until the PIR issues a change to act as a wake up signal.

    I briefly looked at that demo board. I like PIC32's, not sure how much memory it has but you could always add an SD card to get a few spare gigabytes.

    I'm currently working on a solar power monitor, buttons, LED backlight LCD display, SD card, USB, and discrete A2D converter. It takes under a milliamp of current in normal (I'm not busy) mode.
  5. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    What you are really describing; small size - efficiently powered by a small battery - with a camera and ability to transmit a picture - that sounds like you want to start your research with looking at mobile phones. You can probably pick up some old phones and start with how them as a model. What Micros do they use? What Cameras? Also look at LiPo rechargeables instead of an AA cell.

    The only missing components are the Passive Infrared Sensor and an App to wrap up the functionality.

    Most phones have microphones and accelerometers that can be used to stand in for the PIR.