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    MOSFET 12VDC Relay?

    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...
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    MOSFET 12VDC Relay?

    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.
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    MOSFET 12VDC Relay?

    I'm not familiar with simulators but it seems to work?
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    MOSFET 12VDC Relay?

    You may be right. As an example, the data sheet of the LTV-817, CTR is 50% at 5mA min. It's 100% at 10mA, or 50mW. 600% is maximum. Those are at 5V. At 12V, I'm unsure how it is affected, but I expect it is based on the brightness (power) of the octocoupler LED. So, I would expect 12V@5mA...
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    MOSFET 12VDC Relay?

    Hey Harrold. I appreciate your help on this. I believe your idea won't work because the switch is located physically far away from the circuitry. Because it's a retrofit solution it is challenging. The 12V "signal" comes via a single conductor up to 30ft away. It is not a pair of wires and...
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    MOSFET 12VDC Relay?

    Just for an extra layer of safety. The signal wire is fused at the switch, but might be only 20ga.The load conductors are fused as well, but for 10ga loads. I prefer the two to be isolated because it's a harsh environment.
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    MOSFET 12VDC Relay?

    Alright... this is what I've come up with including the optocoupler. I should have downloaded KiCad a long time ago.
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    MOSFET 12VDC Relay?

    Thank you :)
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    MOSFET 12VDC Relay?

    Gotcha. I'm expecting it shouldn't get too hot but one never knows. Since it's being used in the marine environment, I'd like to add tinned blade connectors and encase the whole thing in epoxy.
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    MOSFET 12VDC Relay?

    I think I understand now. R2 pulls up the gate voltage, but R3 pulls it down faster. Elegant solution. I don't think it will work in my situation, but I think the NPN will.
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    MOSFET 12VDC Relay?

    Yes you're right, I was lol. Apologies.
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    MOSFET 12VDC Relay?

    Let me see if I understand correctly. R1 pulls up the gate to keep M1 normally-off. When Q1 is on, it pulls down the voltage on M1 Gate, thereby turning it on. I guess R3 limits current, while R4 ensures that Q1 receives proper voltage? With a low RDSon p-channel MOS, and those 10k...
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    MOSFET 12VDC Relay?

    That's an idea. The thought to use a p-channel did occur to me. I also considered low-side switching with an n-channel. The problem is that neither of these options are "drop-in" compatible with the current setup. The issue with high-side P-Channel: Presently, the 12V relay is normally-open...
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    MOSFET 12VDC Relay?

    Hmm... Well, dang. None of the gate driver ICs I found were rated for continuous duty. Bootstrap also can't do it. It seems like the next solution is a voltage doubler with a either a 555 timer or 4049. The gate current of the MOSFET at 20V is 100nA. I believe either IC is up to the task...
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    MOSFET 12VDC Relay?

    Good question. This is for a sailboat. The only source of power is 200 watts of solar. On long passages, every watt is critical. Right now, automotive relays are being used. But they have drawbacks, including drawing a couple watts each while in use (about 2-3 watts each). There are 5 onboard...
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    MOSFET 12VDC Relay?

    OK... I came up with this schematic. To turn on the MOSFET, the mechanical switch is closed. This sends 6V to the gate via a Zener diode and resistor. The MOSFET is now on. Since the system voltage is 12V, and the gate is at 6V, there still remains 6V potential between gate and source. From my...
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    MOSFET 12VDC Relay?

    I am obviously misunderstanding something then. More information: it's a 12VDC circuit only. No higher voltage is currently available. The gate is controlled with a single pole toggle switch. The MOSFET must be on the high side of the load. If I am switching a 12VDC load, and providing...
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    MOSFET 12VDC Relay?

    For other readers: The answer is yes, it's a problem. Google n-channel MOSFET high side switching. For on-off cycling, the solution can be "bootstrapping" the gate with a capacitor, but it appears that it won't work for continuous duty as the capacitor will eventually drain. For continuous...
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    MOSFET 12VDC Relay?

    In my mind it seems impossible to use the same VGS as VDS when switching a MOSFET. In this case, 12VDC for VGS, and also for VDS, but it could be any voltage. Am I missing something? This is my thought: MOSFET is off. VDS is 12VDC and VGS is 0VDC. 12VDC is applied to the gate, and now VGS...
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    MOSFET 12VDC Relay?

    Well, my anticipated load is actually 5A but I am hoping to build multiple circuits (and spares) that will meet all my power needs. This is for a fully electric sailboat. The D4184 looks like a great choice. Thank you!
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