Idea: Inductively charging a wireless mouse Monday, July 9th, 2007
Posted by carltonstedman in ece, ideas, projects, wireless power.add a comment
So, had an idea for a project. Yes, been done before, but thought it would be a good exercise, at the very least. There are patents out for this type of thing and even a couple of commercial products. But here’s the project goal: Design a wireless mouse battery charger fitting in a mouse pad. Need to do some more research before I can make some formal specifications, but here’s more info on the concept:
- The batteries inside the mouse must be rechargeable.
- When the mouse is on the mousepad, the internal batteries are being charged up.
- The mousepad is powered from the 5V’s off a USB.
- Inductive power transmission is used.
Here’s the gist on inductive power transmission:
- Method for wirelessly transmitting power through the air.
- Primary coil’s voltage is reflected on to the secondary coil, acting as an air-core transformer.
- Losses (through the air) are probably substantial.
I don’t expect this to be the most efficient thing in the world (at least, not at first). Largely, it is a learning experience, strengthening my understanding of magnetics (which is really just a hand-waving at best right now), and something fun to do. I plan on winding my own coils and using minimal money. The primary coil will be in the mousepad. The secondary coil will be in the mouse. The mousepad, unfortunately, *will* need to be plugged in. Either a spare USB port can be used (at first) or I can grab the +5V out of the transmitter, so it only uses one port (eventually).
Hopefully, I can find a mouse with an internal battery charger. If not, I may need to construct a simple switched battery charger, using the secondary coil, or get a cheap IC. I’d rather design my own, if possible, also as a learning experience, if using NiMH batteries. I think I’d stick with an IC (maybe I could get a sample) if it uses Li-Ion. Even better would be if the charger was internal to the mouse itself and I could just supply the voltage with the coil.
I plan on simulating/modeling this project, especially the magnetics. I would like to learn more about magnetic parasitics and model them, such as core losses, winding resistance, et cetera.
Would be a fun project!
Project: Laptop -> Set-top mediabox Saturday, June 9th, 2007
Posted by carltonstedman in ece, ideas, projects.2 comments
So, the general idea is to use my old, broken, crappy laptop, use what I’ve got and make minimal (cost-wise) changes to get a full set-top mediabox (I’ll call it a STMB for short) built up and working. Here’s the general approach:
* No need for internal harddrive (borked anyhow)
* Boot from customized Live DVD (start with just Xubuntu or something)
* Add more RAM (200-pin DDR PC2100) – currently have 256 MB; add 256 or 512 (ideal) MB – going to use RAM a lot, so maybe even get two 512 sticks or whatever (ebay may help)
* Add a PCMCIA->USB 2.0 adapter (it only supports super-slow USB 1.1 right now) [Sabrent makes one that people have got working under Linux: http://www.newegg.com/Product/Product.aspx?Item=N82E16815123021]
* Get the PCMCIA->802.11b wireless working or say “screw it” and just hook in through ethernet cable
* Fix power connector so it’s solid
* Take all components out of laptop case and mount on Lexan or something – just get some scrap Lexan and cut it up to make a “case”, or find some other case (old VCR?) that fits well
* Improve cooling: add more fans or heatsinking
* Setup for just TV-out; need a TV-out cable (lost it); could potentially use laptop LCD (lengthen connector) for terminal/debug or something – could potentially make LCD plug-in-able (make adapter) or use it for a different project
* Setup small “display” on STMB, such as using old VCR VFD (bit bang interface or something simple through parallel port – write simple driver)
* Setup simple IR or RF (ideal) remote – could even use/modify old logitech RF mouse or (better) keyboard
Software – could load most into RAM space at startup:
* ZSNES
* Nesticle or some NES emulator
* Gens
* MAME
* StepMania
* Frets on Fire
* Mplayer
* Simple music player – maybe just a MPD frontend? (could stream to/from SFMB then)
* Very lightweight window manager (just WMmaker?)
* Simple GUI frontend (remote-controllable) that runs when WM starts to run stuff
* SSH/SFTP/SCP server
* Dillo for small HTTP stuff
Idea: ShowerPC Sunday, April 22nd, 2007
Posted by carltonstedman in ece, ideas.add a comment
Listening to: Dope – Die Motherfucker Die
Just had a neat idea for a cool little project. The concept is a ShowerPC. What, pray tell, is a ShowerPC? Well, as the name suggests, it’s a computer made to sit in your shower/bathtub. Actually, more like a terminal really, since it’ll probably just end up being that.
Some uses for a ShowerPC:
- Clock to make sure you aren’t going to be late for work
- Temperature sensor near showerhead/faucet to see if the water is warm yet
- Interface to music collection to play while in the shower
Of course, this is just the tip of the iceberg. Naturally, many more features could be introduced, especially if a full TFT (or something) LCD screen is used. The mentioned features could be used/controlled with a simple text LCD.
Naturally, some specifications are in order:
- Hermetically-sealed
- Decently large LCD text screen (20×4 or more)
- Wireless connection to PC
- Audio output to waterproofed speakers in shower
The wireless connection would obviously need enough bandwidth to play the music, so Zigbee might be pushing it at 250 kbit/s, but Bluetooth could be used at 721 kbit/s or even 3.0 Mbit/s if using Bluetooth 2.0. Naturally, 802.11-b/g would be ideal.
One possible implementation would be to hack a router, install linux on it, and set it up for this functionality. This would probably be the easiest route to go (pun intended). The Linksys WRT54G may seem the obvious choice, since it is the de facto router for hacking. I’d consider the La Fonera, but I’d feel uncomfortable sharing my connection with outsiders and I’d feel wrong just hacking it to disable that feature. DD-WRT on the WRT54G may be an option. The only issue would be, how do I get audio output? Quite a big issue actually.
An option is to not send the audio to the router at all, but just have the router control the audio being sent from somewhere else. A possibility would be some type of “audio bridge” from my PC to the speakers in the shower, perhaps over zigbee or bluetooth, but that’d be a project all by itself, honestly.
Course, could just use an old PC to stream to. This may actually be the best solution. Naturally, a mini-ITX PC or something would be “cool”, but, heck, I could throw some wicked lightweight linux on an old 586 even and it would be fine. Actually, could use an ARM processor, if I really wanted a project! An old laptop might do the trick. Would end up being heavily modified for this situation.
MQP Presentation and NES-PC Wednesday, April 18th, 2007
Posted by carltonstedman in ece, ideas, school.add a comment
Had my presentation for my MQP today. It went well. Emanuel and Cyganski were in the audience and I was worried that their godly knowledge of ECE would make me look bad, but, I was able to successfully field their questions. Now, just need to get the hardware finished working, finish the software and write a ton of paper!
The PCB has been quite an experience. Learned quite a bit, most notably how to use PADS and the reason you give components clearance/relief, especially from planes (oops!). Tons of errors, which isn’t that surprising, since it’s a first rev, but still, a little discouraging. Feel like it’s more of an art project, what with all the scoring and cutting with the X-Acto I’ve been doing! Bah, I’ll get it working.
Had a neat idea of using an old NES case to house a media PC. Thought it’d be funny and cool. Could have an antenna for 802.11 coming out of the case, which would be funny too! Use a Mini-ITX motherboard and DC/DC PSU (with some wall wart or something) and hook it up to a TV, maybe replace the controller ports with USB. Definitely would be a fun project.
Concept: Ultra low power display Friday, March 30th, 2007
Posted by carltonstedman in ece, ideas.add a comment
Had a concept for a very low power display, using an average of under a microAmp. All the parts are really cheap, except for the EPD module, which are currently both hard to find and expensive. Could always use an LCD, but that would make the power usage jump up into the milliAmps. Ah, someday those ePaper/EPD modules will be wicked cheap like the LCDs. Until then, just a concept.
- Microcontroller
- Low power with sleep modes using nanoAmps
- Low voltage
- Ultra low Iq
- Atmel AVR ATtiny might be good
- Need SPI, I2C for RTC
- Just some small Flash ROM for code and minimal data
- RTC
- Low power (< 500 nA are available)
- Serial (SPI, I2C)
- Built in 32kHz oscillator
- Such as M41ST84W by STMicro in SO16 package
- Calculate based on RTC
- Could make it battery or supercap backed up, just in case
- Display
- Ideally, an EPD (electrophoresic display/ePaper)
- Something low-power
- Could display something different on push of button
- Regulator
- Ultra low Iq, on scale of nanoAmps
- Might need charge pump for display
- Power
- Ideally, runs off battery or supercap for very long time
- 10F 2.5V caps are available
- Could re-charge it over USB
- Run off USB while recharging, potentially
- Signal interrupt to processor after voltage drops by quite a bit to tell user to recharge
