Battery powered step counting mini game device


As I am quite new to Arduino I have a few questions on my project idea.
I want to make the following:
A mini game device that

  • counts steps all the time
  • runs of a single 2032 3V Cell
  • doesn't have a real turn off functionality
  • has a display with about 240x128px or 128x64px, draws the image 4-10 times per sec. and has about 5 grey scales per pixel(no backlight)
  • can run at least 2 or 3 months without needing a new battery
  • can communicate wireless to another device(as low power as possible)

I know that Arduinos need to much power for such projects,
so I wanted to ask you if you have any idea how to get something like that done.

If my explanation wasn't good enought google Nintendo's PokéWalker as it is quite
similar and inspired my project.

What kind of microcontroller would I need for that? I guess the biggest problem is the display as it should have about 4-10 refreshs per second.

Hope you know something that fits my idea!

Best regards

225mAh for 90 days.

Do the arithmetic.

"Steps" You mean like a pedometer? Attached to your belt or something?

What could it possibly display that changes 4-10 times per second? What are you looking at when it's on your belt? Why not update the display when something happens (like a step or new wireless data arrves.) Only switch the display on when it's held in a certain way - the step sensor will help determining if it's stationary in your hand being looked at.

Most graphic (pixel-based) displays require a backlight to be visible and it's the light which sucks all the power. Can you think of any LCD you've ever seen anywhere which has greyscale capability and no backlight? Your digital watch still uses 7-segment LCDs because it has to run for years on a tiny battery and visibility is a primary requirement for the watch. Can you do your project with a simpler watch LCD? Even e-ink displays don't have true greyscale.

How big do you imagine this device is? Can you use an Arduino Pro Mini? They can be very efficient when running off a single battery.

A pedometer, exactly.

I just found the Arudino LilyPad SimpleSnap, but I don't know how long it can run off its own battery.

I want a display like the one on the original GameBoy, that I can draw anything on without having to use something like 7-segment or such things, just a smaller resolution and not bigger than 1.7". If there is no display with greyscales I can live without that, but a backlight display would draw too much current from the battery I think (Or is the battery on the LilyPad SimpleSnap that big? o.o).

I would only use the display when I need it, the rest of the time it would be turned off and the device is just counting the steps. Also the wireless communication would just be used a few times a day for a few seconds.

Does the Lilypad SimpleSnap even have enought analog and digital pins to use a display, Accelerometer, some kind of wireless transceiver and buttons?

The LilyPad just doesn't have enough pins for my task, but the pro mini looks quite good to me.
So the next questions are:
-what kind of battery should I use to power the pro mini and how long can it power it?
-what kind of display should I get that doesnt have more than 1,7" and no backlight?
-what kind of wireless communication is cheap, easy to use and doesn't draw too much power?
-what accelerometer that is good enough for a pedometer can run off 5V?

I want to get away as cheap as possible with this project, so the most expensive part will be the display I guess?

the finished device shouldn't be bigger than 5x5x2,5cm if possible.

  1. Battery: do you want rechargeable? A non-rechargeable battery will last longer for the same size or weight. I'm guessing rechargeable might work best for this. Maybe a single-cell LiPo. That has the advantage that you can run a 3.3v Arduino straight from the battery without any voltage regulator to waste power.
    Sparkfun has a pagefull of batteries, with chargers too.

  2. Display: Start with Adafruit Shop Displays and check out the e-ink and graphic LCD categories. They still have small, cheap "Nokia" displays. eBay has zillions more.

3)Wireless: What are you trying to do with wireless?
Is "pairing" a bluetooth device acceptable? The Bluetooth LE (Low Energy) standard is very common now and very good.
WiFi will probably take up too much of your precious battery power but it's what you need if the thing has to connect to the internet and upload data to a server.
More generic radios like RFM12B, RFM69, NRF24L01 or the plethora of 433MHz and 915MHz modules are often used to make a network of sensors around the house or whatever you want.

  1. 5V is not a good choice. Most accelerometers use 3.3V and that's what you want your main processor to run on anyway, to save power. Real pedometers use a mercury tilt switch or some other mechanical thing. I do not recommend you try that method. I like the ADXL345 but that may be overkill for this project.

Read Nick Gammon's excellent page on power saving.

I expect that a Lilypad does have enough pins. I've never used one, but it has the I2C pins available, which allows you to put all the devices onto that data bus. There's 12 pins left over after you connect your accelerometer, display and radio to I2C.

Don't be afraid to make your own PCB. I think it may be a requirement for this project. I've made PCBs for Arduinos that fit inside 9-pin serial plugs and still do useful things.

Thanks for all that help and information.

Unfortunately i just ordered a 5V pro mini, looks like I should cancel that xD

For the transceiver i thought of infrared or something like that, but I'll check out Bluetooth LE.

I'll also check out the ADXL345 as it seems to use not very much power and uses I²C and not analog outputs like the 335.

What part of the project did you think of making a PCB? I made some PCBs in thr past and etched them in my school but they are not as high quality as professional ones. The only thing I could think of making a PCB for the whole think to combine the Arduino with the ADXL345 and Bluetooth and only have the display seperated. But I think I'm not experienced enough for that. Also as I'm still a student with no income I need the things as cheap as possible and can't afford to buy all thr parts from the different modules seperately and put them on a selfmade PCB.

I'll try to get all the parts I need for my project and ask back if I have any more questions, thank you very much!

The ADXL345 as a bare chip is about $7 or on a carrier board $18.

A PCB is $5 per square inch (for three, with free shipping) so you're only talking about $10 worth of PCB at the maximum.

Bluetooth will run about $25-$30.

If you want it small then you've really got to have your own PCB. It's the wiring harness that links all your components together. It can also be a structural component. Without a PCB you've got loose wires everywhere and components hot-glued inside the case.