I have a project that uses two small 12V DC computer fans that combined use under 1000mA.  I also have a Heating pad that uses 12V AC and uses around 800mA.  Lastly i have 6 small lights that use 12V AC and 65mA each.  I am using a motion sensor to turn on the lights and a pressure sensor to turn on the Fans and the Heating pad.  My Arduino controlls it all and the Fan, Lights and heating pad ar connected to external power and use a 12VDC 1A relay.

I am using a standard wall wart that is 12V DC and has plenty of current to drive all my devices.

I use a LM7805 to get a regulated 5V DC for the sensors and Arduino.

My question is...  Should i use a LM7812 to regulate the power for the Fan, Lights and Heating pad?  I'm asking becasue i think that the wall wart will regulate it enough and that using a LM7812 will be overkill...??? 

I look forward to any replies and thanks...!!!

PS - I have been told that even though the lights and heating pad are rated to use 12V AC that they will work fine on the 12V DC.   

Perfect...  Well i hope it works and I'll check back if i have any issues... 

Thanks for the help like always...!!!

Depends on how heavy the dog is.

This brings up another question...  How exactly do these work...?  If it says it will sense pressure from 1 lbs to 25 lbs and the dog is 5 lbs and i have 2 lbs of bedding always over the sensor will I be able to set the sensor to kick on the heating pad if it senses pressure over 5 lbs or does it just measure pressure or no pressure...???

I've used an FSR just once, this one from SparkFun

That is the exact one i plan to use...!!!  Is it a good one to use???  Do you tink if i put it under a piece of linoleum flooring it will be able to determine if my dog is in his house???  How long do you think it will last? Finally I probably have to run a pretty long wire from the arduino to the sensor...  Anywhere from 2 - 5 feet.  Are there any special considerations i need to make to account for this long of a wire? 

Thanks for the reply too...  Its good to hear from someone who has actually used this to have some insight on it's performance...!!!

Why do you want to use and arduino? Is there anything else you want to do apart from firing the relay?

Yea, i am going to use it to to also turn a small fan on/off depending if my dog is present but i dont want the fans to run the entire time...

I kind of figured the arduino replaced the U1 but wasn't sure...  Thansk and hopefully i can work it out...  I'll let ya knwo when it arrives...

I plan on trying to use this SFR with a relay so after looking at the FSR Integration Guide I believe i should follow Figure 14 - "FSR Variable Force Threshold Relay Switch" 

Here is a link to the SFR i plan to use...http://www.sparkfun.com/datasheets/Sensors/Pressure/fsrguide.pdf

I will be using the FSR and an arduino to determine if my dog is in his house and if so to kick on a small heating pad with the use of the relay...  When following the schematic of Figure 14 where does my arduino fit into this and do i have to set it up this way...???  It seems like a lot of stuff to make it work...  I am very new to electronics so my understanding of schematics is limited...

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...??? 

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???

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...!!!

This is probably a very stupid question but I'm new to all this so please bare with me...

I have a breadboard where I have one power rail with 12vdc and the other power rail with 5vdc.  I have a motion detector (PIR) that requires 5vdc and the lights it will kick on require 12vdc.

In an effort to save space i am wondering if I can use the ground on the 12v power rail as the ground for my motion detector.  So i will have the motion detector hook up to +5v from the 5v power rail and to ground of the 12v power rail.  Is this possible...??? Can componets that require 5v use either the ground from the 12v rail or the 5v rail? 

I hope this makes sense and thanks for any info you can provide...

Thanks for the replies as it is helpful information butd not exactly what I think I am looking for. 

The clients will not have access to the circut board or with altering/changing anything on the unit.  I am basically installing the circut board in my final product to do things such as motion sensor lighting, temperature controlled fans, pressure sensors, etc...   The circut board will be enclosed in a project box which is also completely concealed within the larger product.  I understand it may be hard to understand without me releasing what the final product is but i think this is as clear as i can be.  The clients will simply plug in a wall wart and that's all they will have to do with it...

Does using the circut in this type of product still require me to release anything?  If so does anyone have a suggestion on how or what i should use to design a circut board for a commercial product? 

MADWORM - when you say i can have a pcb manufacturer produce the breadboard I made, but just can't call it Arduino or anything similar, do you mean that if I take this avenue that i will not have to disclose anything?  Thanks for the link to the article also.  It was very informative. 

I have searched the forum for help with my question but none of the answers are very clear so I would like to reach out to the community...

I have a product that I would like to sell commercially but I am not sure what needs to be done if i used an arduino to create it.  The main product is not at all an "electronics" product but I used the arduino to help me develop some ideas I had to add some small features to my main product. 

I have basically reproduced an arduino on a breadboard and added some other custom componets (sensors, relays, etc.) as the features of my main product.  I currrently burn the code on the Atmega and pop it into the breadboard that is set up like an arduino.

I have not  started selling my product but I'm afraid if it takes off i will need to outsource this part of my product.  I have no background with electronics or with soldering so I know i would not be able to produce this side of my product for commercial use.

So here are my questions...

1.   Can i legally have a pcb manufacturer produce my version of the "reproduced arduino" and my custom componets?  What will i have to disclose and how or where would i disclose it?

2. Could i sell my product with the reproduced arduino on a breadboard and if so what will i have to disclose and how or where would i disclose it?


3. Can I simply purchase many arduinos and used them directly in my product?  If so what will i have to disclose and how or where would i disclose it?
 
I know i may be a little vague but any help is greatly apprecieated.  If anyone has any suggestions on other options i should look at to take this side of my product commercially I would be open to hear any ideas.   I like doing thinks "by the book" and would rather do things right the first time instead of when it becomes a problem.  Thanks so much for the help...!!!

Thanks for the reply Lefty but i am still a little fuzzy about some things.  I created the circut by reviewing some similar project online but i really dont understand how it works or why we put things where we did.   I attached this pic to help our discussion.

So in the pic Number 1 is one side of the coil and gets the signal from the arduino.  I believe the signal is 5vdc?  The signal comes out of the Arduino, through the resistor, through the Transistor and onto the #1 side of the coil in the relay where there is also a diode connected. 

So number 2 in the pic is the other side of the coil and it is connected to 12vdc and the other side of the diode.

Number 3 is connected to ground of the 12vdc.

Number 4 is not connected to anything

Number 5 is connected to the Ground side of my lights where the hot side of my lights are connected to 12vdc. (the other 2 wires coming from the lights wire are not connted to anything, i just used a old wire i had

 Okay...  here are my questions...

- Since #2 of the coil is connected directly to 12V+ then is the signal from the arduino really connecting the other side of the coil to the ground side?

- Why does the #2 side of the coil have to be hooked up with a diode and not just directly connected to the 12v+?  I understand that the diode keeps a surge from getting to my ATmega but not really how.

- Why are the transistor and resistor needed and how do i figure what values for these componets?  If the amps I will draw change will these values also need to change?

- So if i need a relay and the item I need to turn on is 12v and will draw around 260 mA then I need a 12v relay rated at at least around .5 amps???

- So really simply what I believe is happening is that the lights are hooked up to 12v+ and when the relay is tripped it provides the ground side of the connection for the lights to work? 

Any other tips or suggestions on what relay I should use for my circut are welcomed...  Anyting else you think i may need to know is also appreciated and valued...

Thanks again

PS - how do i insert an image? 

I have a small project where i built a arduino on a breadboard to run a motion sensor then kick on some lights when it detects motion.   the entire project is powered by a wall wart 12vdc 500mA.  The breadboard's power strip on one side has the power regulated down to 5v with a LM7805 to supply power to the motion sensor and the chip and then I have the other side of the breadboard powered with 12v to supply power to the lights.  The lights i plan on using are 12v 65mA and I will have 4 lights.  Right now the signal from the (ATmega328) kicks on a mini relay I got at Radio Shack that is 12v1A.

I think this is the link to the right relay. http://www.radioshack.com/product/index.jsp?productId=2062481#

I have a couple issues with the relay as it clicks really loud when it is triggered and it's leads are really small and do not go into the breadboard very well so i am looking for an alternative.  I really don't know much about electronics so i need help with what relay i need or can use and what all the ratings mean.  I tried looking up some relays on DIgikey and Mouser but with all the filter options i didn't know what i needed. Can someone please help me with what these values tell me about a relay? Contact Rating @ Voltage; Coil Current; Coil Voltage; Control On Voltage (Max); Control Off Voltage (Min)? 


I am also interested in reed relays or solid state relays as they look like they will work better in a breadboards...

Any tips or help is greatly appreciated...

-H-

Is there a simple example using millis() to do more than one thing at a time...???  or even a very basic example doing anything and using millis()...???