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I want to turn on a load of around 1.5A with a reed switch. I tried to just use a reed switch but found out pretty quickly that it will not take the current.

I was considering a BJT but there is a voltage drop across this I would like to avoid.

I have been looking at MOSFETS but all the examples I have seen have the load voltage at around 12V whereas I am turning on the MOSFET with 5V to drive 5V

I could also use a relay but I think the current for this would also be too much for the reed switch.

I am also considering dropping the reed switch for a Hall effect. There is no microcontroller.

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2 Answers 2

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You don't say what the load is, and its characteristics can be a factor in choosing the "right" driver.

Separate from that, there is something called a "logic-level" MOSFET. In round numbers, this is a power MOSFET that is (or is almost) fully enhanced (minimum Rdson) with a gate-source voltage of only 5 V. Infineon is big in this area, partly because they acquired International Rectifier. Vishay also is a player.

Don't discount bipolars. Yeah, they have a base current and a saturation voltage, but a complimentary driver circuit and oversizing the part can take care of those issues. Why bother? For me, its because I still find them more reliable in electrically harsh environments like military surface vehicles and spot welders. Bit if a Vcesat of 0.1 V is too much, then an oversized, logic-level, n-channel, power MOSFET should work.

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  • \$\begingroup\$ It is to turn on an led strip of around 30 neopixels and it's controller. The hall effect will between the battery and LED strip so everything is dead until a magnet comes by. \$\endgroup\$
    – maxum
    Jul 20, 2022 at 4:46
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Reed switches, with 'carry current' ratings up to 5A resistive, are available.

However one, with a much lower rating, may be used to drive a 5V 25Ω relay (coil current 0.2 A), with contact ratings ranging from 2A to 7 A.

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