# Help calculating amperage and choosing power supply

Hello,

I am building a device to push the shutter button on my digital camera at intervals and when there is motion. The device uses a stepper motor with a worm gear from an old 5.25" floppy drive to push the camera button. It’s working great at this point and I am moving the project from a prototype on a bread board to a little PCB and tidying it up.

Part of cleaning the project up is consolidating the power supply. Currently, the Arduino is powered by its battery pack or USB, the digital camera is powered by its batteries and the stepper motor is powered by a 12V, 1.5A wall wart. My desire is to get all power from the 12V wall wart and use a voltage regulator to supply 9V for the camera and Arduino.

I know the stepper motor is 12V at .69A, I don’t know how many amps the Arduino uses plus I have PIR motion sensor which sips power from the Arduino also, the digital camera (Canon PowerShot 2000IS) has a DC input that is labeled 9V but I can’t find the amperage.

So. I guess my question is first am I on the right track, is this a sensible plan? Second, I am hoping someone will venture an educated guess at what the total current draw for this project will be and how big of a power supply I need. I have the 1.5A, an 800mA and a 500mA handy. The two smaller ones are labeled 12V put actually output closer to 16V with no load BTW.

One final question is when I set this up on the breadboard I have a 0V and a +12V rail down one side of the breadboard connected to the 12V DC power supply, and a 0V and +5 rail running down the other side connected to the Arduino. Should the grounds be linked together or not?

I have posted a picture or two and possibly a video if anyone is interested. http://dkdkb.homelinux.com/

Have a great day!
Yertman

DO you have a digital multimeter? YOu can easily measure the usage and add them up :)

So. I guess my question is first am I on the right track, is this a sensible plan? Second, I am hoping someone will venture an educated guess at what the total current draw for this project will be and how big of a power supply I need. I have the 1.5A, an 800mA and a 500mA handy. The two smaller ones are labeled 12V put actually output closer to 16V with no load BTW.

The camera is the big unknown, the arduino board will only draw like 50ma for it's own use. I would suspect that your 1.5A supply would probably work and worth a try.

One final question is when I set this up on the breadboard I have a 0V and a +12V rail down one side of the breadboard connected to the 12V DC power supply, and a 0V and +5 rail running down the other side connected to the Arduino. Should the grounds be linked together or not?

If the +5vdc is derived from the +12vdc power source via a regulator chip then the grounds will have been already 'connected'. If DC voltages are from totally independent power sources then yes grounds must be wired together.

Lefty