Dad911: Heres a link to the regulator. http://www.radioshack.com/product/index.jsp?productId=2062600 I might be able to use a 9v regulaotr but if I see a drop like I do now, it wont work. Didnt have any 9v at radioshack anyway.

rick: So that 10.7v wont be constant? That sucks, I thought I was all set. Can you suggest how I might get a constant voltage >9v out of this 12v battery?

Lube: Its a prototype for a device that will measure temperature, flow rate, and O2 percentage of a gas in a small pipeline. The information is sent wirelessly miles away to a computer that will monitor the values for any problems.

Funny, I was almost sure it was for monitoring the exhaust gases on your Porsche. I was wrong.

Aurel

Radio Shack will have one of these LM317 Got to page 7 to set the output voltage. Note that on page 3 it says VI – VO Input-to-output differential voltage is a minimum of 3.

Now add up how much current will be drawn by all the devices. Multiply that number by the Highest expected input votage minus the voltage you set the regulator to. This wil give you Watts dissipated in the junction of the pass transistor. Multiply that number by 19 deg C per Watt (theta junction to ambient for TO-220) and make sure that number is less than 150 deg C.

Edit: and since you now have measured the current divide the amp-hour capacity of the battery by that number and see how long it will work. :)

Edit: Edit: If you register with TI and put your buisness name along with engineer or student somewhere in the application they will send you samples of almost anything you need.

That's cool! Is this sump'n you can up with or a kit?

Wow rick I didint get all that the first time through but it looks like a good explanation, I will do exactly that.



Lube: I designed, built, and will install the system myself. I just graduated as a mech eng and my company gave me the task and almost unlimited funds to make prototypes for 5 locations (pictures shows one). Each component on the board is anywhere from a few hundred dollars to over a thousand. The great news is that everything works! The SCADA program I'm using is also very cool.

edit: double post

What is the brand and model number of the oxygen sensor? I would bet that it is pulling more than 1 amp @12vdc. If you can't keep the current draw below 1 amp, that regulator wont work, even with a heat sink. I am an electrical controls engineer, and I work with these kind of things everyday. If you can give me the part number for the sensor, I can suggest an alternative way to make this work.