Ground (Loop) Question

I'm just starting out on a bit of a console mod project; and I suspect it will eventually have to use something like an Arduino Pro Mini but for the minute, all I have is my faithful Duemilanove.

The concern I have is this:

In the end I want the 5v supply inside the console to power the Arduino. But because the Due and Pro Mini use power different connectors, it causes me a slight issue during testing/development.

Unless someone has a better idea, I was just going to run the Due from DC wall plug as usual, run the console through it's normal plug and then run the necessary signal/data wires between the Arduino pins and target circuitry... But that leaves two ground loops unconnected (except by the wallsocket/house system). Is this likely to be a big problem?

I suppose the sensible option would be wire a USB connector to +5v/grnd from the console and plug it into the Due. Then when the time came to switch to the Pro Mini, just hack it off and solder the wires direct. Seems like a lot of effort though. ;)

Unless someone has a better idea, I was just going to run the Due from DC wall plug as usual, run the console through it’s normal plug and then run the necessary signal/data wires between the Arduino pins and target circuitry… But that leaves two ground loops unconnected (except by the wallsocket/house system). Is this likely to be a big problem?

Yes it will. You will need a wire connection from any Arduino ground pin to the circuit ground (I like the term circuit common better as there may or may not be any connection to true or house grounding potential) of your console. This is required for the Arduino I/O pins to actually be able to control or read the console control signals.

But that leaves two ground loops unconnected (except by the wallsocket/house system).

Two wire DC wall power module (sometimes called wall warts) have internal transformer so there is no connection from the DC output minus or positive leads to your house ground connection.

Lefty

Ah, cheers Lefty.

I'll go the USB-B plug route I think. Just means I have to locate my power source pins in there before getting on with the fun stuff.

Much appreciated.

I'll go the USB-B plug route I think.

That of course will have to come from a regulated +5vdc power source rather then a 8-15volt power source that the Arduino external power connector needs. So assuming your control box uses regulated +5vdc then that is a great way to power an Arduino. I have several spare USB cables that I have cut off the PC end and use to power arduino boards through it's USB connector. If you are not powering any external loads (LEDs, solenoids, motors, etc) directly from the Arduino then the arduino board should only require less then say 50 ma of current from your control box's regulated 5 volt supply.

Lefty

Yeah, there’s a 5v regulator in the console’s circuitry, thankfully.

I just have to make sure I find the right point to connect at… so that my poor duino doesn’t end up receiving 12v from the power supply. :smiley:

I just have to make sure I find the right point to connect at... so that my poor duino doesn't end up receiving 12v from the power supply.

That is what digital multimeters are made for. If you don't own one then stop all progress and get one, they can be very inexpensive and save you much grief and loss. ;)

Lefty

Hahahah. Thankfully I "inherited" one from a job many many years ago. :)

I'm quietly confident... which is usually the first step towards disaster.

Day one: success!

The voltage regulator was positioned in a really accessible place, so I threw together a fairly long power/ground twisted cable with a USB-B connector on the end, and carefully soldered it onto the 5v and ground pins of the LM7805.

End result - when main power is turned on, the Arduino turns on as well.

I is well chuffed!

Congrats!

I love the feeling you get when an idea comes to (successful) fruition :)

Hahahahah yep. Long way to go, but it's a good start.

And a feeling I'm not used to - normally I break things a few times first. :D