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Relay operations

Discussion in 'General Electronics Discussion' started by franzdrs, Feb 23, 2016.

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  1. franzdrs


    Feb 23, 2016

    I have a question about a two coil latching relay I am using for a project. The relay is used as follows: every few seconds an air humidity measurement is made with a sensor and if humidity is below a certain level one coil in the relay is energized momentarily to switch a fan on. If the humidity is above the level the other coil is energized to switch the fan off. So, every few seconds one of the coils is energized. If the same coil is energized over and over again because the humidity threshold is not crossed, the fan stays as it was. This is what happens most of the time, since only once in a while the threshold is crossed and the other coil is energized.

    So my question is about the specifications for the relay. It says there that the relay contacts have an electrical endurance of so many OPS (operations I guess), depending on the current and voltage. So what counts as an OP? Is it only when the relay changes from set to reset and viceversa, or also when the same coil is energized over and over again (which is most of the time)? My guess is that an OP is only when the relay changes its state, but I would appreciate an expert opinion.

  2. AnalogKid


    Jun 10, 2015
    For the contacts, it is only when they change state from conducting to non, or vice versa. Specifically, the breaking action is the most stressful on the contact plating.

    hevans1944 and davenn like this.
  3. dorke


    Jun 20, 2015
    You can make it with all electronic parts,
    generally a lot cheaper than with a dual coil relay...
    What are the voltage and current of the fan.
  4. sureshot


    Jul 7, 2012
    All electronics part relays are known as solid state types. Depending on load (very important on life) relays contact make and break can top 80'000 switchings. But its very dependent on a few factors, including contact material, and current loads.
  5. franzdrs


    Feb 23, 2016
    Thanks for the answers. Dorke, the voltage and current of the fan would be about 40 VDC and 0.6 A.
  6. dorke


    Jun 20, 2015
    In this case you can use an all electronic solution which would be better in every way: smaller/cheaper/more reliable.
    If you want to go this way and need help,
    please post the circuit that drives the relay.
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