Working BX-24 startup controller

droswell · 12-16-2003, 03:02 PM

I have a Basic-X 24 chip (similar to a Basic Stamp 2) powered directly off my battery (with some circuitry for noise and voltage regulation, of course).

Also, I have 2 solid state relays - one to power on my inverter, and one to power on my LCD/Amplfier.

I use the pins to do the following:

The controller reads a DPDT switch I installed next to my dimmer. If it's in the center position, it puts the controller in "Auto Mode" - that is the computer turns on and off with the ignition of the car. If it's up, it stays on all the time. If it's down, it stays off all the time. The BX chip also monitors the serial port (COM2) of my computer, looking for commands like "shutdown". I have a perl script to watch that serial port and run a shutdown script if it hears that command.

It makes it very easy to throw a couple thermistors on the input lines of the BX and monitor internal heat of the cpu, lcd, and so on. In fact, any analog or digital input signal can be read and manipulated.

It also allows seperate controls of my LCD/AMP and computer, to avoid the nasty pop you get shutting off a computer with an amp still on.

The programming was fairly trivial - not nearly as painful as building an IO circuit to interface with the controller.

So down to my question - I can control the wait time for my controller to monitor the ignition line, thus saving power. I currently draw a constant 32 mA from my battery. Anyone know what the typical current draw for a head unit's accessory wire? (i.e. to maintain the clock) If 32mA is too much I can increase the wait time, but it will cost me responsiveness in my system.

BTW, I live in VT where nights drop to -40F. I'd like to not have to find out the hard way!

Thanks in advance...
DRos.

Ricky327 · 12-17-2003, 10:37 PM

Not sure, but Ill guess its around 25-35mA myself. Best thing to do is measure it

Not so sure what you meant by increasing the "wait time" to save you power?

droswell · 12-18-2003, 06:23 PM

If I send the chip into low power mode for 1 second, it's not as useful as sleeping for 20 seconds, where I use 1/20 the VA. But, my maximum wait time for the computer to even start booting could be 20 seconds, instead of <1.

I could throw my radio back in the car and measure, but I've got 3 ft of snow and it's going to be a pain in my ***. Maybe I should drive somewhere warm for christmas, with all my tools.