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Relay trigger when voltage above 13v

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AVGresponding:

--- Quote from: Zero999 on April 29, 2024, 09:40:57 pm ---
--- Quote from: AVGresponding on April 29, 2024, 04:44:47 pm ---
--- Quote from: Zero999 on April 29, 2024, 08:24:56 am ---The LM386 is an audio amplifier IC. I think you meant the LM393.

Plenty of good ideas have been given above. If you want an off the shelf solution, then you could use a voltage monitoring relay.

--- End quote ---

The LM386 is basically a power op-amp, and would be fine to use for this, though the quiescent current might not be optimal. It'll certainly be better used as this than as an audio amplifier; it's horrible at that

--- End quote ---
I don't think so. I would be difficult to use the LM386 as a comparator. The input voltage is limited to +/-0.4V, it's internally biased, so its output sits at half the supply voltage and the DC gain is only 20. No doubt it can be hacked into a comparator circuit, but it's much easier to just use the LM393.
https://www.ti.com/lit/ds/symlink/lm386.pdf


--- Quote from: Ian.M on April 29, 2024, 02:44:07 am ---TL431, driving the base of a PNP transistor to switch the supply to the relay.  You'll need appropriate base resistors, an anti-parallel diode across the relay coil, and possibly a high value feedback resistor from the collector of the PNP to the TL431 REF pin to add a little hysteresis.  Make the feedback resistor much lower, and once triggered it will latch on, till you momentarily either remove the supply, or ground the REF pin.

--- End quote ---
Like this.
[ Attachment Invalid Or Does Not Exist ]

--- End quote ---

The OP mentioned wanting to use an LM386 because they have lots of them. I always try to answer the question being asked, and not ignore it.

The output biasing is trivially easy to incorporate as part of the design. The input limitations require more thought, the voltage divider values can't be as arbitrary as you could normally get away with. Aside from that, it's perfectly feasible, if not optimal.

Zero999:

--- Quote from: AVGresponding on April 30, 2024, 05:26:19 am ---
--- Quote from: Zero999 on April 29, 2024, 09:40:57 pm ---
--- Quote from: AVGresponding on April 29, 2024, 04:44:47 pm ---
--- Quote from: Zero999 on April 29, 2024, 08:24:56 am ---The LM386 is an audio amplifier IC. I think you meant the LM393.

Plenty of good ideas have been given above. If you want an off the shelf solution, then you could use a voltage monitoring relay.

--- End quote ---

The LM386 is basically a power op-amp, and would be fine to use for this, though the quiescent current might not be optimal. It'll certainly be better used as this than as an audio amplifier; it's horrible at that

--- End quote ---
I don't think so. I would be difficult to use the LM386 as a comparator. The input voltage is limited to +/-0.4V, it's internally biased, so its output sits at half the supply voltage and the DC gain is only 20. No doubt it can be hacked into a comparator circuit, but it's much easier to just use the LM393.
https://www.ti.com/lit/ds/symlink/lm386.pdf


--- Quote from: Ian.M on April 29, 2024, 02:44:07 am ---TL431, driving the base of a PNP transistor to switch the supply to the relay.  You'll need appropriate base resistors, an anti-parallel diode across the relay coil, and possibly a high value feedback resistor from the collector of the PNP to the TL431 REF pin to add a little hysteresis.  Make the feedback resistor much lower, and once triggered it will latch on, till you momentarily either remove the supply, or ground the REF pin.

--- End quote ---
Like this.
(Attachment Link)

--- End quote ---
The OP mentioned wanting to use an LM386 because they have lots of them. I always try to answer the question being asked, and not ignore it.
--- End quote ---
Using a part, just because you have loads of them, is normally a bad idea.


--- Quote ---The output biasing is trivially easy to incorporate as part of the design. The input limitations require more thought, the voltage divider values can't be as arbitrary as you could normally get away with. Aside from that, it's perfectly feasible, if not optimal.
--- End quote ---
Alright then, post a schematic. Show me how you would do it.

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