Comment on What is negative voltage?

• JelleWho@lemmy.world ⁨5⁩ ⁨days⁩ ago

  This explanation is good indeed.

  Sometimes you design a circuit where the main chip runs on +3.3V reference to the chips ground at 0V, but somewhere in the proces you end up with an extension board that wants 5V below the ground. For easy of use we just call this -5V instead of renaming everything to 0, 5, and 8,5V. Renaming also has the drawback that I like to measure everything reffering to the ground of the main chip. So I personally just don’t rename and keep my reference there.

  source

  • CetaceanNeeded@lemmy.world ⁨4⁩ ⁨days⁩ ago

    Just so I understand.

    In your example, let’s say we have a power supply that distributes 5v and 8.5v.

    The extension board is easy, we just hook it up from 5v to 0v.

    For the 3.3v chip, are we wiring it between 8.5v and 5v? So it only sees a 3.3v voltage difference?

    source

    • JelleWho@lemmy.world ⁨4⁩ ⁨days⁩ ago

      Correct.

      A good ‘at home’ example is your computer power supply

      source
    • TBi@lemmy.world ⁨4⁩ ⁨days⁩ ago

      Yes. That will give you a 3.5v difference.

      source
• yetAnotherUser@discuss.tchncs.de ⁨4⁩ ⁨days⁩ ago

  If you (or anyone else) wants to check their understanding of voltage as the difference between two electric potentials, here’s a couple exercises I stole from a text book:

  (Note: Electric potential is also measured in Volt.)

  A battery has a constant voltage of 1.5V between its plus and its minus pole. What is the electric potential of the minus pole compared to ground potential when:

  1. The battery is on an electrically isolating mat?

  Solution

  The battery is not connected to ground. Therefore, no statements about the electric potential of either pole can be made.

  2. The minus pole is connected to ground?

  Solution

  Because of the connection, the electric potential of the minus pole equals that of the ground, which is by definition 0V.

  3. The plus pole is connected to ground?

  Solution

  Now the potential of the plus pole equals that of the ground. We know that the voltage difference between the plus and minus pole is 1.5V. Since this difference is measured by subtracting the potential of the minus pole from the potential of the plus pole the equation: 1.5V = p_plus - p_minus = 0V - p_minus => p_minus = -1.5V. Therefore the potential of the minus pole is -1.5V.

  4. The plus pole is connected to a generator producing an electric potential of 10,000V compared to ground?

  Solution

  Now the electric potential of the plus pole is also 10,000V. The potential of the minus pole must be 1.5V lower, so it must equal 9998.5V.

  source