protect arduino from negative voltages

rubendelacosta · Joined: Dec 25, 2005 Posts: 153 Location: lisbon

hi

i've been playing with arduino to generate CV and i'm a bit concerned about negative voltages.
i've put a op-amp working as a voltage follower on every out put, but maybe it needs more protection.

thanks,
ruben

skrasms · Joined: Feb 21, 2008 Posts: 121 Location: Portland, OR

State Machine · Posted: Mon Feb 01, 2010 6:55 pm Post subject:

If you want to protect the digital outputs of the MCU, then use a 74HC244 octal buffer and hang 100 ohm resistors in series with each of the buffers outputs. Just tie pins 1 and 19 to ground so the device outputs are not tri-stated. No sense using an op-amp when you can get 8 buffers in a single package using the HC244 chip.

If your using one of the 3.3 volt Arduino variants, there are plenty of choices for 3.3V bus logic as well.

Over the years, I have always used bus logic to protect the more expensive, and generally more sensitive, processing circuits within a circuit card. Plus I can drive higher capacitive loads, such as back planes, using these buffers.

Bill