12v power supply - mini car computer

DShannon

Hi All,
I have used the BOE and BSII to build a mini car computer (temperature, compass, etc). Now I want to actually put this in the car!

2 questions:

1) Can I directly hook up a "hot" wire (for example splicing the radio power supply) and ground to the BOE 9 volt battery clips? Will the BOE and STAMP regulate this to 5V?

2) When power supply is removed, and then applied (eg, stopping and then restarting the car), will the STAMP reset and then execute the stored basic program?

I am a bit new to this, so any guidance would be most appreciated.

THANKS!!!
-Dan

The Dead Bug

Yes and yes.
The Stamp is rated from 6 to 24 volts if you connect through the battery connector.

It will run your program from the beginning at powerup.

Bruce

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Name: Bruce Clemens

Work:· Clemensb@otc.edu
Good Stuff on my Bolg: http://theDeadBug.journalspace.com

Chris Savage

Dan,

·· Car electrical systems are usually pretty noisy environments...I would recommend finding a decent regulated or switching supply circuit on the internet somewhere designed for automotive use (Use Google).· Splicing to·the "radio power" would reset the stamp during startup of the car.· The only way to prevent this would be to connect either directly to the battery, or to a post in the fuse block that comes from the battery.

·· Bear in mind, depending on the current draw of your circuit, you could risk running the car battery down overnight.· I went through this on a car computer myself some years ago.· Only minimal circuitry was powered on during the off-time of the vehicle.· I only wish I had a Stamp back then, because of it's low power mode.




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DShannon

thanks DeadBug, Chris,

Chris I am newbie, so i am not sure what you mean by "regulated or switching supply circuit". would this be same as putting a capacitor between the supply and the BOE?

-dan

Chris Savage

·· There are 2 basic types of power supplies you could use.· Regulated & Switching refer to how the power supply maintains it's rated output voltage.· That's a little beyond the scope of this discussion, but you could always do a Google search to learn more.··I know someone recently posted a power supply circuit in another thread for automotive use...I think it was from an LCD site.

·· What I mean is, instead of trying to power your circuit directly from the car's unregulated/unfiltered voltage, try to find a circuit for a supply which will give you adequate voltage and current while filtering the input.· I myself in the past built a power supply that provided +12V and +5V @ >1A for powering my TTL and controller circuitry.· Control of things like the cars lighting system was done by MOSFETs and Relays, which were controlled by the MCU.



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Mark G

Scott Edwards Electronics www.seetron.com

follow this link for an app note "Vehicle 5V power supply"

http://www.seetron.com/an_vpwr1.htm

DShannon

Thanks Mark,
Being a newbie, I am not sure if I would need linear or switching supply configuration? How would I determine this? Do I need 1 or the other?

thanks everyone for their help.

Chris Savage

Dan,

·· Just stick with regulated for now.· The supply mentioned in the link above (Thanks Mark) is a regulated supply.· Switching supplies are usually better when you need higher current.· In my auto computer I got around that by using 12V & 5V regulators on all the sub-system boards.For example, on one dash panel, all the LEDs were powered by their own regulator (Configured as a constant-current source).· Later it was modified to allow for brightness changes, but still had it's own supply.



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