Recent content by adamq

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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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