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Topic: Car Keypad (Read 38372 times) previous topic - next topic


May 14, 2009, 02:22 pm Last Edit: May 14, 2009, 02:42 pm by neonpolaris Reason: 1
Thanks for taking the time to help me like this, I really appreciate it.

I may have to turn my nano sideways to fit the inductor on there.  I have room on the bottom of the board for the smd components, but I dont think I have enough room on the bottom for that.

Thanks for catching my capacitor boo boo, I would have been displeased when (if?) I figured that out.


Ok, here's my cart, take 2.

I'll have to wait until I get home to see how/if I can make all that fit on my board/box.


i make this sugestion to every1 doing a car project. Get another car battery for your project. that way, you dont have to replace your car's so often ;D


thats why this forum exists, or?  ;)

could be that it never has shown with the smaller cap, but you never know...

now the cart is good  :)



I removed a pin from the Nano to route the power to the backlight better.  I'll just rip the pin out of the headers that I mount the Nano on.  Since I removed the hole in that spot, I won't be able to forget to do this and feed 12v into a digital pin.


i make this sugestion to every1 doing a car project. Get another car battery for your project. that way, you dont have to replace your car's so often

[smiley=huh.gif] That doesn't make any sense.


Okay, new board ordered, new parts ordered.  Now I wait for a month...

If I get time to cut the hole before my new board gets here, my old one is going in in the mean time.  I'll just plug the new board in when it gets here.  I'm already glad I made it modular. :)



i make this sugestion to every1 doing a car project. Get another car battery for your project. that way, you dont have to replace your car's so often

That doesn't make any sense.

what do u mean?


What he means is that it doesn't make sense to add another car battery just for a project.

When you say wouldn't have to replace it as often, I assume you mean one of two things:

A: The car's battery would be drained by the electronics.
B: The battery will be worn out more quickly by the extra load.

The battery in a car gets recharged constantly as the car is being ran.  So it wouldn't be drained by the project.  Car batteries aren't replaced because they run low like some AA's in a gameboy.  They are replaced because, like any rechargeable, they stop holding a charge after a length of time, or charge cycles.  Really, the only time a battery is being discharged in when your car is off, or being cranked.  After that, the alternator supplies enough power for everything.  You can crank a car, then remove the battery entirely, and it will continue to run! (assuming your alternator is healthy)

As for B, the amount of current that these projects pull is relatively low.  Simply turning on your radio easily pulls more than my whole project.  Turning on your headlights, even more so.

So adding another battery to power these projects wouldn't make sense.  The car's battery keeps itself charged, is already there, and isn't adversely affected by it.  (would barely even notice)

Also, from your post here:
You shouldn't really control voltage with just a resistor.  The reason is that your voltage with fluctuate depending on how much current your load draws at the moment.  Take a look at Ohm's Law, it will explain it fairly well.  This is why voltage regulators (such as the 7805) are used.  They hold output voltage steady independent of load.


My redesigned board should be in next week, but since it's a direct swap for the other board, I see no reason to wait for it.

So I finally cut that scary, scary hole.

I was somewhat torn between putting the keypad underneath the door handle, and next to it. Most people I asked seemed to like it underneath, while I kind of preferred next to. Well, inside the door there is this "stuff". It kind of looks like metal painted on the inside of the door skin. For strength? Sound dampening? Something else? I don't know, but it made the door skin much thicker there (underneath the handle), so my decision was pretty much made for me.

Close up of metal "stuff".

Here are my practice holes. This allowed me to not only get used to cutting with my Dremel, but also work out the exact shape and size I needed to cut. I used the thin metal cutting disc for the Dremel. It worked well.

Here's the door with my template on it and taped up a bit.

Hole cut.

Looks a bit rough. (those marks below the hole are just dust)

The hole retaped, rough edges filed, and paint cracks sanded away.

Retaped and primer paint applied (to inhibit rust)

Dried and untaped.

Last shot of keypad and clip.


Back of keypad up inside the door.

Keypad on door. (not as crooked as this picture makes it look)

And a nice wide shot of the door.

Hopefully my next update will be when I have the wiring finished!


WOW, thats nice  :)

reminds me of that song "the first cut is the deepest"  ;)


Jun 14, 2009, 07:13 pm Last Edit: Jun 14, 2009, 07:40 pm by neonpolaris Reason: 1
[size=14]CODE FINISHED![/size]

Ok, after many hours yesterday, the keypad is wired in.  It works fully, and I finished ALL the software for it.

But it wasn't easy.

You see, I realized that on my board that I have for the car, I can't connect the arduino to the keypad AND the arduino to the PC.  The plug connections interfere with each other.  This would not be the case with my latest board (that HAS shipped now, but isn't here yet)  I really wanted to see what was going on, to make writing and testing new features better, so I made ANOTHER test keypad.  This was made strickly with what I could get from Radioshack (expensive) THAT DAY (I had those headers already).


I really didn't want to pull the real keypad back out of the door anyway.

With the help of my new keypad, I have finalized my code.  I've tried my best to emulate the Ford Keypads as much as possible.

To unlock the car, type in the 5-digit 'factory' code.
To lock the car, press the last two buttons together.

After too many unsuccessful attempts to type in a code, the keypad will flash and ignore input for one minute.

Program up to three additional 'user' codes (stored in EEPROM):
Type the 'factory' code, then 1, then a new 5-digit code, and finish by pressing one of the first three buttons.
Your new user code is now saved to that position.  The car will confirm by locking and unlocking the doors.
You can overwrite the code by saving another to the same position.

Erase all user codes:
Type the 'factory' code, then 1, then press 1 again and hold for two seconds.  The car will confirm by locking and unlocking the doors.

Time out (reset input keys) after programmable time (default 5 seconds).  All key presses must be pressed within
this time from each other to be considered together.  The backlight will turn off after timeout.

The finalized code is in the door, fully working.  When I get my new board in and fix a problem with my wire mounts in the door I'll post pics of the wiring side.


Jun 14, 2009, 07:18 pm Last Edit: Jun 14, 2009, 07:30 pm by neonpolaris Reason: 1
My code is too long to post on this forum.  You can find it here:


If you forget your key how will you start the car?


The keypad doesn't let you start the car.  It just lets you in the car.  It's great if you just need to get something out of the car and you don't have your keys on you.  It would also be handy if you happen to lock your keys in the car.

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