Need AC and DC for project...???

I've had great success with this forum and I need your help once again please...!!!

I am trying to create a project that uses an Arduino, a motion sensor (PIR) and a pressure sensor (FSR) which all need DC current at 5V.

I need the motion sensor to kick on 2 - 7 tiny lights (12v AC 65mA each), and the pressure sensor to kick on two small computer fans (12v DC .5mA each) and a small heating pad (12v AC 800mA).

I currectly have the lights and fans switched on/off via a relay for each and it works great...The lights and fans currently work on DC but I've been told that the heating pad will only correctly work with AC current and wanted to get some advise before i began adding it to the project.

I need to only use one main power supply because I can't have more than one plug to plug in.

SO... what should i do and how do i do it...??? Should i use an adapter (wall wart) to bring in power to my project and then somehow output some AC current to power the heating pad or should i bring in AC currect and somehow convert it to DC to power the arduino and sensors...???

Looking forward to some replies and thanks for the help...!!!

I think your heating pad could work on DC, there is no physics law that state against it. Have a link to datasheet or part number?

I checked with the manufacturer and they did not have a datasheet to give me but here is a link to the product below... They said if i could find out exactly what information i am looking for that I could call them back and obtain the information and they gave me the direct number to call for the technical rep. to contact. What do i need to ask in order for you to determine if it will work or not...???

http://www.thepetstoreonline.com/petsafe-php00-11248-universal-pet-bed-warmer.html

Basically what I am trying to do is to put this in my doghouse and add a pressure sensor controlled by the Arduino so that the heating pad is only on when my dog is in there... The pad has a cord that attaches to an AC adapter so I think I can just install a Size N Coaxial DC Power Jack (available here from Radio Shack http://www.radioshack.com/product/index.jsp?productId=2102599) and then run power to it via this jack from my circuit... Does this sound like it will work...???

What makes a product run from AC and DC current and will there be anjy dangers of running a product on DC rather than AC???

Just connect it to DC power supply that you already have in your project, and test it. I'm sure it will be o'k with DC. Than use relay or mosfet to control it by arduino.

Things like heters and lights will work quite haply on AC or DC. They can both be run at the same voltage because the way we define AC is in terms of RMS. However the actual voltage in the unit will be lower when using 12V DC than using 12V DC. It is cheaper to get AC from the mains than to get DC.

Yes the project is quite feasible and it should all be able to be run off DC.

You guys are fast... thank you...

So will there be any saftey concerns with providing the heating pad with DC current..??? I don't want to fry anything or catch anything on fire...!!!

Also, if the AC adapter that comes with the heating pad Outputs - 12v 800mA then this means the current draw of the heating pad will be around 800mA correct...? Will i need the same 800mA of current for the heating pad if i us DC current adn if not how much should i plan to need...?

I am really confused about the difference between products designed to use AC current vs. one designed to use DC current... Why would you have one over the other. I understand the cost issue but what happens in situatiuons like mine where you need DC for the sensors and AC for motors etc...???

So will there be any saftey concerns with providing the heating pad with DC current

Yes it will be safer because the voltage is lower.

if the AC adapter that comes with the heating pad Outputs - 12v 800mA then this means the current draw of the heating pad will be around 800mA correct

It is safe to bet that it will be less than 800mA, possibly only 500mA. At that you would be putting 6W of heat into the pad.

designed to use AC current vs. one designed to use DC current... Why would you have one over the other.

Some things need AC, some need DC, some things like heaters and lights don't care. You need AC if you are going to have a transformer somewhere to derive other voltages. Some motors need AC in order to get the right magnetic field. Others need DC, or electronic components usually use DC.