Arduino 12v and 5v control question

[tobes49]

Hi again,

My parents have got a unit with all the router / ADSL / Network equipment in. This can get very warm on a hot day so i'm building them a little temp controlled fan to keep the temp under control.

In the unit one of the power supply's is 12v which is great to power the fan
Also the router unit has a USB socket which I'm hoping to use as a 5v feed to arduino/ATmega328

I've done a quick design:

Fan control circuit

Fan Control.jpg (51.22 KiB) Viewed 1335 times

Question is because I will be removing the arduino and just using the ATmega328 chip can I power the chip from the 5v on the USB port
And use the the separate 12v to power the fan?

[adafruit_support_bill]

can I power the chip from the 5v on the USB port
And use the the separate 12v to power the fan?

Yes, but be sure to connect the grounds from both supplies together. You do not have them connected in your diagram.

[tobes49]

can I power the chip from the 5v on the USB port
And use the the separate 12v to power the fan?

Yes, but be sure to connect the grounds from both supplies together. You do not have them connected in your diagram.

I thought they were connected by the earth strip on the breadboard?

In the proto version I'll run a dedicated earth feed to the mosfet and T off to the arduino/ATmega (because the earth to/from the mosfet will carry the most current)

[adafruit_support_bill]

I thought they were connected by the earth strip on the breadboard?

Looking closer, they probably are. Unless you have one of the breadboards with split power/ground rails.

There are some breadboards out there where rails are split in the middle. It is easy to test for and can be fixed with a couple of jumpers. But it is difficult to track down wiring problems if you are not aware of it.

[tobes49]

I thought they were connected by the earth strip on the breadboard?

Looking closer, they probably are. Unless you have one of the breadboards with split power/ground rails.

There are some breadboards out there where rails are split in the middle. It is easy to test for and can be fixed with a couple of jumpers. But it is difficult to track down wiring problems if you are not aware of it.

I've only got a 400 point breadboard (Fritzling defaults to a 800 point)

Cheers for pointing that out

[Franklin97355]

If you plan to use the chip alone you will need to make allowances for the fact you are not using a crystal or add a crystal to your circuit.