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MOSFET 12VDC Relay?

Discussion in 'Power Electronics' started by adamq, May 4, 2021.

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  1. crutschow

    crutschow

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    May 7, 2021
    The TS wants to use his switches in there original configuration, where a plus voltage from the switch activates the relay, which is why I added the transistor to provide that polarity operation.
     
    adamq likes this.
  2. Kiwi

    Kiwi

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    89
    Jan 28, 2013
    Sorry, but I can't see the real advantage of replacing simple reliable relays with a cobbled together electronic circuit that is likely to cause issues.
    Fitting another solar charging system might be a better alternative?
     
  3. crutschow

    crutschow

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    15
    May 7, 2021
    What issues?

    What is a "cobbled together" circuit as compared to a regular built circuit?
     
    Last edited: May 10, 2021
  4. adamq

    adamq

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    Dec 17, 2013
    Which issues are these? Why do you think they're likely.

    The advantage is a 10% efficiency gain...in some cases, potentially more.

    They're a drop-in replacement connected with blade terminals. Not only could I have spares to swap out, I could also keep the old relays. I don't see the disadvantage.
     
  5. Kiwi

    Kiwi

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    89
    Jan 28, 2013
    Years of experience with DIY solutions to "improve" perfectly good working systems.
     
    Harald Kapp likes this.
  6. crutschow

    crutschow

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    May 7, 2021
    So it's just a broad-stroke criticism.
    He wants to improve the efficiency, so I don't see his system as "perfectly good".
     
    adamq likes this.
  7. adamq

    adamq

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    Dec 17, 2013
    Ah I see. I'm sorry you've bad such bad DIY experiences. I've had mostly good ones. It does often take a few revisions to perfect, but that doesn't bother me. Besides, I enjoy the troubleshooting and learning process--it's one of my hobbies.

    I understand that on land or in a car, the 2.5-4W watts consumed by a relay is moot. On a 30ft sailboat with finite solar capacity, though, it can make a massive difference. Solar panels are often damaged by storms or rogue waves. The sails cast shadows on the solar panels for parts of the day. Consecutive cloudy days can also happen. Solar capacity can easily be halved or totally destroyed, leaving only the house batteries. Although I'll try to fit a solar array of ~300W, I'm trying my best to stay around 100 watt-hours per day of consumption.

    So, the 2.5W-4W (per device) really can make a big difference. It can mean the difference between being able to activate AIS or not. When I'm 1500km from the nearest coastline, in pure darkness or a storm where I cannot see over the crest of the next wave, AIS can tell me whether or not there are cargo ships within a 10km radius, and what our closest point of approach will be. That same AIS can also allow me to sleep for 20 minutes at a time. It's pretty important stuff.

    I appreciate your input. For my purposes, I really don't see the downside. It's a drop-in, plug-and-play replacement module for an automotive relay. If it causes me trouble, it's a matter of putting the original automotive relay back in. As I see it, I can benefit greatly at zero risk.

    Certainly we can disagree on whether this circuit is necessary/useful, but that's just a matter of opinion/preference. On the other hand, if you truly anticipate functional problems with this circuit, please share your concerns so that I can find a solution to them.

    Cheers :)
     
    Last edited: May 11, 2021
    crutschow likes this.
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