Making a Smaller Passive Key Fob

[chrisgonzales]

what i'm doing this sec...

working on getting a solid "case" first then gonna try to spruce it up,

3d print noob here... i suck at complicated 3d programs so i use mostly sketchup as i'm familiar with this for some woodworking projects i've done.

Once i get something i feel will work, ill see how i can share my work via online 3d print services or print them and send out

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[chrisgonzales]

not an electrical engineer but can anyone explain the reason for 2 batteries is it raising the required voltage or just more mah cuz the board has technically 3 contacts 2 negative and 1 positive just curious of the design. The OP got to work with 1 battery does that just mean it will last 1/2 as long, curious as i'm designing this if its worth figuring out a design with both batteries.

 

[Ruiner46]

The batteries are probably wired in parallel, which essentially doubles the battery life. So yes, the battery will only last half as long with a single battery.

Interesting project. It looks to me that the PCB could be reduced in size greatly if redesigned without buttons. It's hard to say if it could be cut down in size without probing a few things. Just after a first look, you might be able to cut just the center area out around the buttons and major chips. However I'm not sure what the purpose of the big trace is that goes around the perimeter of half of the board. Looks like some kind of shielding. It's hard to follow the traces in the blurry pics but I might tear apart one of my keys and take a look to see if it can be cut down. Can someone grab the numbers on all of the chips so I can try to ID them?

I'm an electrical engineer who has done PCB design for the last 10 years.

 

[Lost Cosmonaut]

I'm guessing the trace around the perimeter would be the antenna.

 

[chrisgonzales]

The batteries are probably wired in parallel, which essentially doubles the battery life. So yes, the battery will only last half as long with a single battery.

Interesting project. It looks to me that the PCB could be reduced in size greatly if redesigned without buttons. It's hard to say if it could be cut down in size without probing a few things. Just after a first look, you might be able to cut just the center area out around the buttons and major chips. However I'm not sure what the purpose of the big trace is that goes around the perimeter of half of the board. Looks like some kind of shielding. It's hard to follow the traces in the blurry pics but I might tear apart one of my keys and take a look to see if it can be cut down. Can someone grab the numbers on all of the chips so I can try to ID them?

I'm an electrical engineer who has done PCB design for the last 10 years.

Yea not sure what each thing is for i just assumed the portion around was an anetnna or something attached is a photo and what i could read with zooming in using my phone as a magnifying glass

keyfob by chris gonzales, on Flickr

use the link to view the larger image

 

[Ruiner46]

Thanks for the picture. Unfortunately I'm coming up with nothing on the chip numbers. Still working on it, but now I have to do much more painful searching and all I have to go on is the one brand I recognized - nxp semiconductors. This looks to be a 2 layer board, so that big trace is probably the antenna. I'm not an RF guy though, so I'll show this to some guys at work and let you know if we figure anything out.

 

[chrisgonzales]

Thanks for the picture. Unfortunately I'm coming up with nothing on the chip numbers. Still working on it, but now I have to do much more painful searching and all I have to go on is the one brand I recognized - nxp semiconductors. This looks to be a 2 layer board, so that big trace is probably the antenna. I'm not an RF guy though, so I'll show this to some guys at work and let you know if we figure anything out.

Awesome i plan on making a case for no modifications to the board first just to accomplish that, and then make it small as possible would be neat as well. If you need more pics let me know i can try to get some more tomorrow which my dslr and better lighting

 

[SK GT]

How do you sit down on your wallet and not crush the tape version? Great idea though. The fob is huge compared to my wife's murano fob

 

[Agent_S550]

This thread, much like the BCM hack thread, is really ground breaking IMO. If we can find a way to create/redesign the fob and place the redesigned assembly into a small condensed case, it could be a huge aftermarket development that not just Mustang owners would like to have. I would love to have what amounts to something the thickness of your average ID badge or RFID gate key to start the car. I could at that point only have my wallet on me and function with that.

 

[JakePSD]

This thread, much like the BCM hack thread, is really ground breaking IMO. If we can find a way to create/redesign the fob and place the redesigned assembly into a small condensed case, it could be a huge aftermarket development that not just Mustang owners would like to have. I would love to have what amounts to something the thickness of your average ID badge or RFID gate key to start the car. I could at that point only have my wallet on me and function with that.

BCM hack thread? Now I need to do some searching, that sounds interesting.

I agree that this could be a great aftermarket thing for all vehicles with similar setups. It would be very convenient. I've had my car for pushing a month now and still haven't put the fob on any key rings. I usually just keep it in my pocket, which gets uncomfortable at times driving a forklift for 8 hours at work.

 

[Agent_S550]

My pockets at work are fortunately empty since I have my own office but it'd be nice to keep a small card in my pocket and know I have access to the car. Regardless, I would gander to say it will require some fairly substantial electrical engineering knowledge to backwards engineer a new design.

BCM hack thread is in the DIY thread. You use ForScan and a bluetooth OBDII MS-CAN adapter. You can edit values to turn on and off multiple different functions. Pretty neat. Letting them get a little bit farther along before I jump in and adjust my car to my liking.

 

[chrisgonzales]

This thread, much like the BCM hack thread, is really ground breaking IMO. If we can find a way to create/redesign the fob and place the redesigned assembly into a small condensed case, it could be a huge aftermarket development that not just Mustang owners would like to have. I would love to have what amounts to something the thickness of your average ID badge or RFID gate key to start the car. I could at that point only have my wallet on me and function with that.

That would be awesome and beyond my expertise, i'm trying to print a case thats thinner than the large fob we have now without buttons. I need to do some research if i can find stronger 3d printable material for thin areas or a service only i can try with what i'm doing right now it's probably gonna be 1cm in thickness, so 50% reduction. The battery and coiled copper square thing take up the most space at the moment. Trying to do a no mod to the board case first

 

[fionic]

BCM hack thread? Now I need to do some searching, that sounds interesting.

I agree that this could be a great aftermarket thing for all vehicles with similar setups. It would be very convenient. I've had my car for pushing a month now and still haven't put the fob on any key rings. I usually just keep it in my pocket, which gets uncomfortable at times driving a forklift for 8 hours at work.

not really a 'hack'.

http://www.mustang6g.com/forums/showthread.php?t=61773

 

[Agent_S550]

not really a 'hack'.

http://www.mustang6g.com/forums/showthread.php?t=61773

Hey I'm trying to make you cool and trendy. If I just said "Yea they logged in, punched some numbers, and boop". If I called y'all hackers and car ninjas that sounds way cooler. Take credit when it's due. ;)

 

[fionic]

Hey I'm trying to make you cool and trendy. If I just said "Yea they logged in, punched some numbers, and boop". If I called y'all hackers and car ninjas that sounds way cooler. Take credit when it's due. ;)

didn't mean to sound like an asshole, thank you though

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