SensingBench electronicsTest and identify
Hall sensor
Also called hall switch, throttle hall, lid sensor.
Senses a magnetic field. Laptop lids, BLDC motors, scooter throttles, some washing-machine drum sensors. Analog halls (throttle) and switch halls (lid) are different, and the pinout of a 3-pin SOT-23 is not something to guess from color.
If you are new to this category
A sensor reports a condition such as weight, light, temperature, or position. Many sensors do not switch fully on or off. A kitchen scale bar, for example, changes by thousandths of a volt. Keep the small board that read the sensor if you still have it.
Keep the connector. Write down the wire colors before you cut them. If you do not know which wire is which, the sensor is hard to reuse.
Red and black feed the sensor a steady few volts. Green and white are the tiny signal, measured between them, not from either one to ground. Pressing the bar changes that signal by millivolts. A normal meter on DC volts can show that it responds. Turning it into a number on a screen wants a small amplifier board, often an HX711.
Strong neodymium magnets. Hard-drive magnets slam together hard enough to blood-blister skin and shatter into sharp chips. They also wipe media and bother pacemakers.
| What to look for | Usual figure |
|---|---|
| Throttle | Often 5 V supply and a 1–4 V output that moves with the magnet. That is an analog hall. |
| Motor halls | Three digitals plus supply, often 5 V, open-collector or push-pull |
| Laptop lid | A tiny switch hall. The matching magnet is in the lid, and it is easy to throw away. |
Volts are electrical pressure, amps are how much current is flowing, and ohms are how hard the part resists that flow. A higher voltage than the part was built for is how salvage parts die on the bench. If a cell in the table says “read the stamp”, that stamp is the whole specification.
What people actually use it for
- Keep it with the motor or throttle it came with
- A contactless limit if you already know the pinout
Leave this one when
Unmarked SOT-23. The chance it is a hall and not a transistor is not high enough.
Buying a new one is the better idea when
A known A3144-class switch or an analog hall with a datasheet.
How to tell if this one still works
Only with a known supply voltage. Watch the output while you bring a magnet in. If nothing happens at 5 V it may be a 3.3 V part, or it may not be a hall.
Tools you will want: Meter, 5 V, Magnet.
Words on this page
Short meanings, so the rest of the entry is readable if you are not already doing this every weekend.
- BLDC
- Short for brushless DC motor. See brushless. The 'DC' does not mean you can hook it to a battery with two wires.
Where people actually find it
1 notes, most useful first. “Leave it” means the part is in that machine and you should not take it: it is dangerous, worn out, or only useful if you already know that exact repair.
| From | Call | How many | How often | Where it sits |
|---|---|---|---|---|
| E-scooter or hoverboard | Worth it | 6 | always | Inside each hub. |
- In this particular machine
- Three halls per motor, on the small plug.
- Where to look
- Inside each hub.
- How to get it out
- Do not cut the plug off.
- The condition to expect
- Good.