Bond Gadget: Using an Arduino in an Old Car

Hi Everyone,

I have a (for you probably very easy to answer question). It was a while since I did electronics and I am still reading up on it again.

Here is my project. I have an old car and it shall look as it was old as well (also after I am finished with all the work).

I want to add a little fun extra, like a bond gadget. I have currently an unused (don't know why) switch on the dashboard.

This is what I want to do: When I use the switch I want a new radio to appear from a hatch in the middle. The mechanics I can do. I have a question to the electronics.

The car is an old car (with plus on the chassis which I will rewire) and 12 V. How does it now work with the arduino uno. Do I need to power it separately and then use a relay to work the engines or can I use the 12V from the car battery to power it and so to speak integrating it to the cars electronics (its from the 60s so the electronics of the car is not as sensitive as modern cars)? I want the cars 12V to power the little motors that operate the hatch and mechanical parts. How does it work with the switch, it is currently connected to the cars 12v electronical system obviously, can I use the same switch for the arduino or will the resistance be too high. Did I miss a major thing?

Any tips or ideas are greatly welcome.

Thanks!

You really shouldn't need a microcontroller and associated software for something like that... You've got a switch with 2 states and a mechanism with 2 states.

You need a couple of limit switches to shut-off the motor when it gets to the end, and you'll need a relay or two to reverse the motor. I haven't got it fully figured-out, but I think a couple of diodes could allow it to operate in the "other" direction after you've hit the limit switch in the 1st direction.

It would be easier if you had a 3-position center-off switch (like a power window switch), but you might be stuck with what you have.

If you do need some logic circuitry, you don't need a programmable microcontroller.

The car is an old car (with plus on the chassis which I will rewire) and 12 V. How does it now work with the arduino uno. Do I need to power it separately and then use a relay to work the engines or can I use the 12V from the car battery to power it...?

  1. You can power the Arduino from 12V. The circuitry runs off of 5V, but there is a 5V voltage regulator on the Arduino board.

  2. You can't put 12V into an Arduino input. If you can re-wire the switch (so it's not directly connected to 12V) you can use it. Or, you can use a voltage divider (2-resistors) or a resistor & diode to knock-down the 12V to 5V.

  3. The Arduino doesn't directly put-out 12V or enough current to power a motor. You can use a Transistor, MOSFET, or a relay with a 5V coil (with a coil rated at 40mA or less) to switch a motor. Since you need to reverse the motor, you'll more than one relay/semiconductor. You can reverse a motor with a bridge-circuit (4-transistors or 4-MOSFETs) or with a DPDT relay, plus another relay to turn the motor on/off.

HI DVDdoug,

thanks very much for you detailed answer. Already clarified a lot!

I want to use micro controller. I find this is a lot of fun learning! Also, I probably will need more than only one motor and maybe I can add other functions later.

So to sum up 1) I can power the arduino with the car battery 2) I need to do something with the input signal from the switch to the arduino 3) I need to do something with the output signal from the arduino to the motors.

Thanks a lot again!