Newbie Question: Changing Circuit without damaging the board?!

Hi Guys,

Yesterday was my first day with my new Arduino Uno ... I successfully completed my first 4 projects (LED lights) and now I am planning to work on more serious stuff.

To move from a project to another one, I am following this sequence:

  1. Disconnecting the USB with the UNO is executing the current project (project # 1)
  2. Change the circuit to that of project # 2
  3. Write and Compile the new code of Project # 2
  4. Connect the USB again.
  5. Upload Code of project # 2

I am worried that between step 4 and 5, the UNO will be executing the code for project # 1 on circuit # 2 as I haven't uploaded the new code yet.

I am just wondering if there is a safer way to change circuits .. I am sure that at some stage I might damage my UNO.


If you're really worried about it you could upload the blank BareMinimum sketch to the board although unless you have something either very sensitive or very heavy duty connected I'm not sure there'll be a problem.

Why not simply disconnect circuit 1, upload the code for circuit 2, then connect circuit 2 - hard to damage hardware that isn't connected.
(well, it is relatively easy if you smack it hard enough with some ESD, but that isn't the Arduino's problem)

There's usually no need to worry unless circuit 2 has some way of damaging itself (might be issue with a motor controller or other high power circuitry), or if circuit 2 has a complex chip that could be misprogrammed and then stop functioning (usually this means another microcontroller or programmable sensor)

The outputs from the Arduino don't really have enough power to damage things (except themselves if shorted out) - if you want to be extra careful put 1k resistors in series with all the pins (both protects the circuit and the Arduino chip in case of a wiring/programming error).

Ok Thanks for your input guys,

I am wondering about the "reset" button. what does it do when pressed? and can i use it to return to manufacturer settings i.e. the blinking 13 pin program?

I am wondering about the "reset" button. what does it do when pressed?

It resets the processor - nothing at all to do with "factory settings" - it will simply restart whatever program was last burned into the device.