A promise that, in the future, it will be better

September 4, 2013

Elizabeth came on my podcast to talk about Dolores, an older neighbor who lives alone. We got to talking about a device that would let Dolores maintain her independence while reassuring her family (and Elizabeth) that she is fine.

The idea is similar to the thinking-of-you jar I’ve been working on to explore the Electric Imp. Essentially, add an accelerometer, put it all into something cute (i.e. a teddy bear), have Dolores pat it when she wakes up (or if it is in the kitchen, when she walks by). If Dolores doesn’t pat it by 10am or three times a day or (setting to be determined), it will contact her family who can call and checkup on her.

This isn’t a hard concept. And I’ve been scooped a bit by Goodnight Lamp. (Hmph! People who take my ideas and go back in time to make them!) But their solution is pretty expensive (~$150) and I think I can do something for $80 from off the shelf parts.


On the podcast, I said I thought it would cost around $80 to do a handcrafted one and my total here is $81. Yay estimating skills! Oh, I forgot:

  • Adorable receptacle: priceless.

On the show we also talked about features:

  1. Dolores would pat the bear.
  2. WiFi or other configuration to be set up by a daughter, Elizabeth, or other caregiver.
  3. Bear will also light when people hit a website (so the thinking of you functionality).
  4. System will message daughter (text, email, phone) if Dolores doesn’t pat the bear before certain times. (No check-in)
  5. System will also message daughter if bear is not charged or service is down for some reason.
  6. Daughter can see when the bear was patted (to verify system is working).
  7. Chargeable: 1 week of battery. Plugged in via USB wall wart.
  8. If battery is low (1/3 usable charge remaining or 3 days), system will email Dolores.
  9. If the battery is very low (2 or 1 day of battery left), system will email daughter.

Some I added later:

  • The bear will respond to a pat with an LED light (white if tricolor, green if red-green).
  • If the bear’s charge is low, it will respond to a pat with a blinking red light.
  • If you keep patting, the bear’s LED turns yellow. After thirty seconds of intense “patting”, the bear turns red and messages the family.

None of this is all that difficult. I looked at the Electric Imp hardware. I need to add battery monitoring so I’ll learn their Sampler class. And I need to add an I2C accelerometer but I already made an I2C LED work so I do not expect a problem. Much of this is server side, the agent software that I’ve been avoiding. I know in theory how to do it but I suspect the practice will be like hitting my head on a wall a few times.

Some of the work will be electronics: the battery is usable from 2.8V to 4.2V, the ADC input to the Imp presumably can’t go above it’s operating voltage (3.3V) so either I need to sort out a level shift (resistor divider? but that is a waste of power!) or figure out where else I can monitor power (maybe going into the Imp, on the April board?).

Also, I know an accelerometer is overkill, especially three axis ones; there are other motion sensors. On the other hand, I know how to use an accelerometer really well and I’ve got many lying around. Though I wonder… a temperature sensor would cost nothing but it takes longer to work and breaks my patting method.

Also, since the unit is going to be sleeping most of the time (for power reasons), the pat needs to wake it up. The Electric Imp has six pins available. I’m using 2 for I2C to the accelerometer, 1 for monitoring battery voltage, and 3 for the tricolor LED. If I need the accelerometer to interrupt the processor, I’m going to need to go to a bicolor LED so the user will only see red, green, and yellow. I think that is ok. But it makes me wonder if the accel really is the way to go. I don’t think I want a simple push button switch (not cute). Well, I need to go look at force sensitive resistors and soft potentiometers. Though how those are going to wake up the processor, I don’t know.