How does this ultra simple board use magnetics to trigger an On / Off function? - Page 1
Forum section: electronics / projects

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: August 23, 2025, 02:51:20 am
content: Hello,The schematic below is from a dehumidifier and is the auxiliary board to the main PCB. It is situated just above the water bucket in the dehumidifier. It is used to display color lights in a dehumidifier and also to turn the dehumidifier off when the bucket is full.In the bucket is a float with a small magnet in the top. Somehow, as the magnet gets close to the board it shuts the dehumidifier off.I am referring to the small, SOT23 device next to the capacitor marked a U1.However, that device is marked 2313z and I can't find any SOT23 Hall Effect devices matching that number.When tested, it tests as a Zener Diode, so I assume that's what it is.I can't find any documentations that describes any way to use a Zener diode as a Hall Effect sensor. So I cannot see how this circuit achieves turning the dehumidifier off when the bucket is full?If someone could give me a little assistance on this I would be grateful.Thanks

author: Psi
author_rank: Super Contributor
timestamp: August 23, 2025, 02:58:41 am
content: It's got to be a hall effect switch/sensor. Just one that is hard/impossible to find any info on.Are you sure the chip says 2313z

author: amyk
author_rank: Super Contributor
timestamp: August 23, 2025, 06:30:31 am
content: Fromhttps://electronics.stackexchange.com/questions/647407/help-identifying-hall-sensor-95b2hwe find thathttps://www.major-power.com.tw/page/4/Hall%20ICuses that marking scheme, and further searches reveal another companyhttp://www.senkomicro.comwhich seems to be a clone of them (e.g.http://www.senkomicro.com/upload/2021/02/20210202093347.pdf). If your part was from a device manufactured around the 3rd week of 2021, that would also line up.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: August 23, 2025, 02:38:37 pm
content: Thanks for the replies.I tested the device (U1) under the assumption it might be a Zener Diode and it tested precisely as if it were.Could a Hall Effect device test in such a manner as to perfectly mimic a Zener Diode?And if it's not a Hall Effect device then I see no way the circuit could sense a full bucket even though there is a magnet in the top of the bucket float.

author: amyk
author_rank: Super Contributor
timestamp: August 24, 2025, 02:18:10 am
content: Not sure how you determine it's a zener, but most if not all ICs will have ESD protection diodes on their pins.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: August 24, 2025, 02:32:44 am
content: Using this schematic, I tested it and every test with my VOM matched the results I would expect to find it it were this Zener.I do not believe a Hall Effect device could test this way?But that would defy any idea I could come up with as to how the magnet would cut off the dehumidifier when the bucket was full.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: August 24, 2025, 02:37:02 am
content: Could U1 be one of these ?The more I study the connection configuration and the block diagram, the more it seems to match.https://www.mouser.com/datasheet/2/115/AH3522_AH3524-3401236.pdf

author: amyk
author_rank: Super Contributor
timestamp: August 24, 2025, 04:28:49 am
content: That part doesn't have a matching marking, but it's probably something similar to that.

author: mikerj
author_rank: Super Contributor
timestamp: August 24, 2025, 07:51:10 pm
content: If you applied sufficient voltage to cause something that looked like a zener or avalanche breakdown then it might not be working any more. Inspection of the circuit should tell you it isn't a Zener (or pair of Zeners); it has a supply pin, a ground pin and an output pin with a pull up resistor which is exactly what you'd expect from a 3 pin hall effect switch IC.

author: ThermallyFrigid
author_rank: Frequent Contributor
timestamp: August 28, 2025, 01:23:29 am
content: Quote from: mikerj on August 24, 2025, 07:51:10 pmAwesome.That settles it.Thank you!