Using latching Hall sensor to toggle a LED - brightness issue

Question

I'm using a U18 latching Hall sensor (datasheet) to toggle a LED. I'm driving it off a 6V L1016 battery.

My issue is that the LED is very dim.

My understanding is that the U18 limits the output current to 20~ish mA. In theory my LED wants 20mA forward current.

So I am not sure why it is not very bright. Testing the LED directly with the same battery both 150 & 300 ohms resistance it's much brighter.

^{simulate this circuit – Schematic created using CircuitLab}

Original and tidied-up schematic.

How can I make this brighter? Would the best solution would be an op-amp? Is there something else I've overlooked (in terms of setting it up incorrectly)?

Answer 1

The hall sensor is not designed to have enough current to drive an LED.

You need to use a small mosfet or transistor so that you can have the right current on the LED.

If the output is an open collector output, you can do it with a PNP (supposedly you want the led on when it activates.)

Answer 2

Output current at 5V is 5.5 mA. It's also an open collector output, so it pulls to ground when triggered. Your schematic as drawn would not work. At minimum the led is backwards.

Answer 3

That device has an open-collector output - the LED and its current-limiting resistor must be connected between the positive supply and the device output terminal - like so:

^{simulate this circuit – Schematic created using CircuitLab}