Project Logs

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• counting machine

  matt venn • 08/18/2014 at 16:28 • 0 comments

  Here's that link I was talking about earlier - a cool little toy for your kids. I'm thinking this will make a good front panel for this project.

  http://boingboing.net/2011/08/25/kids-counting-box-press-the-big-buttons-to-incrementdecrement-the-total.html

• power supply

  matt venn • 08/13/2014 at 21:34 • 0 comments

  I'm fairly sure I can get something that fulfils the previous log's specification using the Pi Supply: http://www.pi-supply.com/product/pi-supply-raspberry-pi-power-switch/

  I think I'll need to cut a usb cable and split the power out to the pi supply. Then the data can go through to the Pi. The power will go both to the battery and the Pi Supply. That way when the unit is plugged in it will charge the battery.

  I'm still unsure of whether I really need the Pi Supply. I might be able to just solder some wires onto the power switch of the battery, then the Pi can turn it off.

• power specification

  matt venn • 08/06/2014 at 14:45 • 0 comments

  I want to get on with the box design, but I think until I finalise how the power handling stuff is going to happen I can't. I've been over a couple of Raspi power solutions:

  http://www.pi-supply.com/product/pi-supply-raspberry-pi-power-switch/

  http://pi.gate.ac.uk/pages/mopi.html

  but I'm not sure if either will really do what I want. So this log is trying to commit to a specification of what I need, so I can work towards a solution. I really want an 'off the shelf' solution rather than having to build something myself. This is because I want the project to appeal to people with little electronics experience. I want people to think 'that's a cool idea, I'll try it' and be able to order consumer stuff, have it delivered and plug it in.

  So anyway, what I need is:

  • A button to turn it on,
  • A way of it turning itself off so it can avoid SD damage etc,
  • A socket to charge it up (ideally USB so I can use the chargers I have),
  • Ideally the same socket to connect it to another computer for updating/connection.

  If anyone knows something that can do this, please post a comment!

• speaker hacking pt2

  matt venn • 08/06/2014 at 14:39 • 0 comments

  I somehow smoked the HXJ8002 chip on the pcb in the speaker while testing the battery stuff in the previous post. The datasheet of the part is here.

  I tried to source just the chip, to repair the board but couldn't fine them in low quantities. Instead I bought a new board from deal extreme.

  It's coming from China so it will be mid August till I can test it.

• speaker hacking

  matt venn • 07/11/2014 at 07:41 • 0 comments

  To reduce power consumption, I wanted to check if the mini speaker I bought would run without a battery. This way I can leave the speaker in the on position, and power it via its usb socket. Only when the system turns on will the speaker turn on. And it won't waste energy by charging an additional battery we don't need.

  Opening the speaker was easy, and it has a tiny Li-Ion or Li-Poly battery. It measured 3.7V, and the open circuit charging voltage was 4.7. Cutting the black battery wire I checked it would run powered at 5V - which works. This draws about 100mA during loud moments.

• battery testing

  matt venn • 06/29/2014 at 09:35 • 0 comments

  After some bad experience with the 18650 battery format, I thought it best to do a tear down on the battery pack I finally decided on. The tecknet usb power pack comes in various sizes, but the smallest 3300mAh version will run a model B pi for 6 hours. I'll probably switch to the model A in future for even longer run time.

  You can read more about it here: https://github.com/mattvenn/tecknet

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