Car Keypad

Thanks!

So the 1N diode keeps the current from flowing backwards, the zener diode would cut out voltages above 15v, and the choke would clean up the power a bit. What exactly do the two different caps do? Decoupling to clean up the power? Something else?

I assume that everything to the right of C3 I should ignore, as I don't want to reduce the voltage to 5v?

Yes, you dont need C3,IC1,C2 when it should only protect :wink:

L1 blocks HF noise (should be 2A cappable).

the 1N makes in case somebody messed up the polarity a safety, and in case the input drops it prevents the C1 from getting discharged.

D2, can also be a 20V type, this limits the voltage.

C1 (Ultra Low ESR) smoothens out small ripple.

C3 could be removed, but im used to always put C3 and C2 with a 7805 :slight_smile:

Maybe I'll work this into my board when I get home. This would mean waiting another MONTH before I could install, though. Ugh.

Nice and clean prototype work, First class job.
Keep on building,
make stuff.

KG2

hmm, nice =P

where did you make your own pc board =D

id like to make my own ;D

I used BatchPCB.com, which is a service of SparkFun. It's relatively cheap, but it takes a month or so to get your board.

You'll need to learn Eagle (or similar). There's a tutorial on PCB layout using Eagle on SparkFun's site here:
http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=109

wow >_>

well, i can wait a mont to get started on arduino sheild making lol

Would this work for L1?

And for C1, can I use a ceramic here, or only electrolytic? I'm thinking of longevity and temperature sensitivity, but I'm not terribly sure of when I can use one. If ceramics are non-polar, can they always replace the others, but not the other way around (like when dealing with AC)?


Edit:

Ok, here's the cart I'm looking at, ignore the amounts:

I may not have room for that choke on the board!

yes, that L1 looks good!

for C1 it should be a ultra low ESR electrolytic. Thats becouse they are like the "fastest" and you can get them with big F values.
elextrolytic is fine, as long as you dont take the super cheap ones.
my C1: http://shop.conrad.at/ce/de/product/445903/KONDENSATORULTRA-LOW-ESR220F35V
its rated with 6000h at 105°C, that should be enough...

in your chart you have a 220pF, what should be a 220µF :wink:
and with a 20V zener diode your still safe but it will not be so close to trigger unwanted (14,4V is quite common in a car)

thats how this looks in my prototype:

(my 1N is a little oversized, had no smaller around ::))

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.


Edit:
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? :wink:

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

now the cart is good :slight_smile:


Imgur

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. :slight_smile:

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:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1239996764/13#13
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!