The apartment building I live in uses RFID tags to allow access to the pool area, and they only give out one per apartment. I live with two other people, and this becomes kind of a pain. I found an RFID spoofer for Verichip tags, so hopefully this works for me (if it doesnt, ohwell! it helped me learn to design better PCBs).
Here is a link to the original site and schematics:
Please take a gander and let me know what I can do to improve my design. I will likely etch this board at school, so Ive tried to keep most of the traces on the bottom, so will only need to do a transfer for one side (and I can just hand-draw the couple of traces on the other side). I also wont be silkscreening, but I would like to design the PCB with all the labels, as if I were sending away to BatchPCB to have it made.
A couple of points - Ive heard from people around me that its good to use straight lines, and ive heard from others that non-90° corners are fine too. I think using lots of 90s looks better - which is the proper way to design a board like this (sub-MHz frequency)? Also, is there a grid size that it is considered ‘proper’ to use for pcb layout? I found that I had to drastically reduce the grid size to line up the header labels with the text.
You could make the board single sided with no trouble. You can run traces between the PIC’s pads.
I would also make all my trace bends 45 degrees.
To save space, you can mount axial components vertically.
I would also move the transistors and associated parts up near RB3 to avoid noise. Move the LEDs down to make room.
Also, I’d find a case for the board before you make it. There are lots of hand held cases available and they often give you a PCB outline that fits. Then redesign your board to fit the case. Beats trying to find something that will work after you’ve built it.
On the effectiveness of this device, I’m not sure it will work for HID tags/readers. Since HID is the most common supplier, I suspect it will disappoint you.
Finally, an editorial note: the original author likes to use the word steal a lot. I would be very careful with this device as it may be illegal to use.
I noticed him saying how it could be used illegally; however, we are all allowed in the pool area, and we can use the one key to let eachother in, so I dont forsee a problem with using it (if it does work). Worst case scenario they take away the tag and we cant use the pool, which we cant get into anyways (because one roommate always has the tag)
You mention that it may or may not work for HID tags; do you know of any way to determine the frequency of one?
Thats a good idea about finding a case first! Ill keep an eye out for one.
One last thing - whats the minimum distance I should keep between traces and pads? Like running a trace between the pads - I was unsure if that was alright to do or not.
If you won’t have a soldermask, try keeping more clearance between the pads and the ground plane, or you might accidentally create a short when soldering.
Philba is right, the board can be easily made singlesided (good components placement job 8)).
The minimum distance between traces, as well as the minimum trace and drill size are given by the board manufacturer. If you plan on using BatchPcb, simply read the FAQ on their website
Ah, last note: the labels for capacitors, and the “NPN” and “PNP” for transistors seem to be too small. This is not a major fault, but if you actually want them printed, I suggest you increase the font size.
HID tags used for the common “card key” systems are 125 khz so you will need to change the frequency at the least. I believe there is a layer of encryption that is used. You may be able to record the tag’s signal but if they’ve implemented some sort of challenge/response mechanism, you are SOL. I’d be surprised if they didn’t but dumber things have happened - cf the MIRT system.
On the illegality issue - it’s not building a device but rather how you use it.
Sorry to wake up an old thread however the original designer, Jonatan Westhues, made some newer versions of the device. The ultimate being the ProxMark3.
That device is a software defined radio which turned out to be a quite handy when researching RFID protocols. The device costs about 450$ and that’s probably too much for the topic starter’s purpose.
If you’re interested in RFID cards, the techniques and protocols used then check out www.proxmark.org. A lot of information regarding high and low frequency rfid cards can be found in the forum: http://proxmark.org/forum/
