Long Range Key Fob with USB Receiver : Hardware/Software Design Thread

maxer6 · 05-03-2005, 07:43 PM

I decided to post this here for suggestions on how to improve the design, I’ve wandered the forums for long enough I will finally post something to contribute to the community. I might produce these and sell them (or give away the instructions) if there is enough interest. I'm looking into designing a Key Fob to control my carputer.

Specs (so far):
USB Interface on the Receiver (So it is easy to use - and will fit in most configurations)
Compact design on both the Key Fob and Receiver
1 to 5 Buttons on the Fob (Maybe more)
Long Range Operation (3,000+ Feet)

Some ideas I was thinking about:
Making the Fob a 2-Way device: Status LEDS & Control Buttons
Possible Signal Boosters
Having the option to turn boosters ON and OFF
Having the option to turn the Fob's Receiver ON and OFF
The Decoder/Encoder ICs have 8 data pins, so we could have 8 outputs and 8 inputs
If someone can find a small (good looking) Key Fob the supports more than 5 buttons let me know.
Put an inductive charger in the fob and making a charger for the car

Below is the possible hardware it would use:
RF Transmitter IC: $05.95 (3,000 Foot Range)
RF Receiver IC: $09.80 (-116dBm)
Button Encoder IC: $3.10
Status Decoder IC: $3.10
USB Module IC: $11.80 (Includes DLLs, and Programmers Guide)
SMB LEDs: $? (Depends on Type)
FOB Case : $2.42
Battery Clip: $0.24
PCB Boards: $?
SMD Antenna: $01.75
Signal Booster(ea.): $13.95 (+18dBm)

Currently the ICs would be from linxtechnologies.com unless someone can point me towards a I2C Long-Range-RF / USB / Encoder-Decoder ICs.

Foreseen QA:
Will you release the Schematic? Maybe, there is a good chance of it since I am such a big fan of open source
Will you release the Source Code? Maybe, there is a good chance of this too. (Read above)
How much will it cost? I don't know yet (<$100 for a RX/TX set); I usually sell things cheap, so it would be the cost of parts (+shipping) plus a little extra for all the work
Will you sell these as kits or pre-built? Probably both
Why not make it WiFi / Bluetooth Compatible? I'm not that good of a programmer/EE, unless someone can find a WiFi/Bluetooth IC that is long distance, easy to use and cheap.
Why put switches on the boosters/receiver? Those devices would always use power (unlike the transmitter - only on when sending), so they would run the batteries down faster.
How long will it take to complete this project? Not long, summer break will be here very soon.

My programming skills don't go very far into hardware interfacing (unless it already has a VB Module), so I may need help from someone on how to use the included drivers (part of the USB Module). And although I have made a few breadboard projects and stuff, this will be my first time with smd ICs and inkjet transferred PCBs: so it's should be an interesting (hopefully fun) project.

jimlad20 · 05-03-2005, 07:51 PM

I have been looking for something like this for ages, what do you intend for it to control? Media functions??

Keep us posted i am very interested !
James

maxer6 · 05-03-2005, 07:58 PM

I have many relays in the car that are controlled by my custom media software, so I was planning on using this fob to unlock/open doors/trunk, start the engine, play my stereo, alarm, neons, headlights, and other stuff like that. but it should be able to control just about anything. For my software I was going to make something like the following:
the four outer buttons control basic stuff(locks, engine, trunk) and then if you hit the center button once followed by an outside button there will be a different function, and hit the center button twice - annother function and so on. But that would be easily configurable throu code, you can make the buttons do anything

jimlad20 · 05-03-2005, 08:11 PM

Yeah great, will the fob actually be able to transceive at 3,000 Ft i know these fobs now a days are good but 3,000 ft Good? so when your engine is cranked (via Remote) this will also start your carpc will it?

maxer6 · 05-03-2005, 08:15 PM

The document I am reading for the transmitter module says 3,000 ft (but you how those things go -striat unobstructed line), but that was why I thought maybe throw in a booster. I always leave my carpc running so I can call it :-) (carpc hosted website comming soon), but it could power it up (using a spare data pin).

jimlad20 · 05-03-2005, 08:24 PM

Lol Carpc Web hosting service, there maybe a market for that! well i'll be very interested to hear any further developments and will be on the look out for a decent Fob.

James

Bugbyte · 05-03-2005, 08:32 PM

I'm interested in using a remote to pulse the startup regulator (Carnetix 1260) to tell it to start the PC. I understand Opus has similar functions. With that kind of range, I could start the PC from my office window and have it running when I got to the car.

jimlad20 · 05-03-2005, 08:39 PM

http://cgi.ebay.co.uk/ws/eBayISAPI.d...sPageName=WD2V

would this be useful at all? i know the fob looks a bit crappy but could this be turn into a usb device?
just a though as i was looking around.

maxer6 · 05-03-2005, 08:50 PM

Looks good but it's not usb, you would have to put a usb chip to it or go through the parrallel port. The 5 buttons on my remote ( http://www.polycase.com/fb20-prod.asp ) match the buttons on my shifter more closely. I can get empty key fob cases or ones with close range boards already installed. But I do agree that is a much cheaper rought.

jimlad20 · 05-03-2005, 08:56 PM

http://cgi.ebay.co.uk/ws/eBayISAPI.d...MakeTrack=true
they also do 4 CH with built in relays. You have got me thinking now!!! time for a new project me thinks!! my Girlfriend's gonna love me!!!

KyleYankan · 05-03-2005, 10:57 PM

jimlad20, post back how well that works. I was consdiering getting the 12ch one. I was also consdiering screw it and going with a tablet pc via wireless

mushin · 05-04-2005, 01:43 AM

I'm not quite sure what I'd do with it, but it certainly sounds cool.

If you need help with the programming, I may be able to help. Sounds like the USB module comes with an SDK, which (hopefully) should make interfacing with it straightforward. I could also help you with the software interface, which I imagine will be something along the lines of tying fob input to keypresses or socket output. PM me if I can help.

Chris31 · 05-04-2005, 02:26 AM

Ok, Im alittle bit confused here.

The receiver module is USB? This means the PC must be on.
How are you going to transfer the command from USB into the relays?

Before you can do anything the PC must be on? unless you have another output from the receiver thats dedicated for turning the PC on.

Would there be any output that will control a relay directly?

Vchat20 · 05-04-2005, 07:46 PM

yeah. maybe you could have it self maintained (own seperate power supply and no direct need for a connection to the computer) so that one or two controls can be made for say remote start and whatnot. and then when you start the car, the computer comes on and connects to the receiver so that the rest of the keyfob buttons will work with the computer.

jimlad20 · 05-04-2005, 07:58 PM

Quote: Originally Posted by KyleYankan

jimlad20, post back how well that works. I was consdiering getting the 12ch one. I was also consdiering screw it and going with a tablet pc via wireless

ok on that KyleYankan i'll let you know how i get on, but my plan is to just have the fob Start/shutdown and restart my carpc. I'll use a RF 2 ch relay reciever hooked up the power and restart pins on the motherboard. It won't be usb its not possible to power the machine up by it thought it should be able to resume from Hib i think!!!