Member Since: February 18, 2008

Country: United States

  • Nathan explains the methodology in the arduino source for the bare 7-segment display. http://www.sparkfun.com/products/9483

  • That 10k is pulling the reset line up, not limiting current to the package. I can only assume it’s PWM with a low enough duty cycle. The reason I ask is that I was considering building a similar ‘backpack’ with a couple of extra things on board, using the same ATMega to drive the display as run my own program, instead of having two 328’s doing what one should be capable of. I think that by using a 1/7 duty cycle, I can protect all segments with only 4 resistors. I will probably go this route since I can’t find anything outlining how to ‘safely’ power leds from 5v with no resistor (only pwm).

  • This may be a daft question, but how are these boards powering the leds without current limiting resistors? Does the ATMega not supply enough current to worry, or is PWM limiting enough?

  • That is the exact power supply that I’m looking to build, for the same purpose of powering XBees. I’m a bit unsure what I should have for Vripple and Fmin. Can you tell me which components you used?

  • I just did this upgrade yesterday, thanks for the writeup. One note I feel I should add is about removing wires from the bulb holders. I found that fishing around in there with a little screwdriver wasn’t working well for me, it either wouldn’t release the wire or I would bend the metal inside so that the new wires wouldn’t stay.
    I found that if I simply twisted the wire (spun) while I pulled out, it came out with no issues.
    Good luck everyone!

  • Ah, so the footfod only transmits when it detects motion(makes sense), and driving the car isn’t enough to set it off. That’s just about perfect then, isn’t it?

  • @CHaskins: Be careful, alot of cars turn off their cigarette lighters then the car is off. Mine does, and that would mean that it wouldn’t work for this project.
    @Nate: At the end of the article you mentioned an extra bit of code that unlocks the car every 10 seconds until the car is started. I didn’t see anything that sensed the car being started, so I assume that it constantly does this while you’re in the car, it is just ignored while the car is on. If this is the case, that 3v lithium battery will die much faster, you should think about powering off of the 3.3v available from the Arduino.
    Also, remember that with this installed, it’s pretty hard to leave your car unlocked. It will be unlocking as you walk away and then relock 25 seconds after you’re out of range. Probably not a problem since you’d have the iFOB with you, but something to remember.

  • It seems that the LCD used in this project is only sold without the backpack, and the backpack is only sold pre-attached to the “huge” graphic LCD. Can we get them sold together or at least the backpack sold by itself? Pretty please?

No public wish lists :(