Hall Effect A3144 - latching circuit ?

Hello. Please can someone advise a circuit to latch the high output of an A3144 Hall Effect sensor ? Using a thyristor maybe ?

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Jan Cumps over 3 years ago +1

You could use this circuit, that uses asingle opamp as Set-Reset with configurable input HI level: https://www.edn.com/use-an-op-amp-as-a-set-reset-flip-flop/ Take care that you configure the output…
rsjawale24 over 3 years ago +1

Hi! You can use an SCR for latching. SCR's latches once triggered unlike BJTs. You can find many SCR based circuits on the internet. For triggering the SCR, you can use an opamp based comparator and connect…
RobinHart over 3 years ago in reply to dougw +1

The basic concept is for a single LED to light when a magnet is close, then stay on with the magnet removed, the circuit would be unlatched (LED extinguished) with a manual button press.

0 Jan Cumps over 3 years ago

You could use this circuit, that uses asingle opamp as Set-Reset with configurable input HI level: https://www.edn.com/use-an-op-amp-as-a-set-reset-flip-flop/

Take care that you configure the output pull-up voltage of the sensor in range for the input of the latching circuit.
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0 dougw over 3 years ago

What would you like to use to reset the latch?
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0 rsjawale24 over 3 years ago

Hi!
You can use an SCR for latching. SCR's latches once triggered unlike BJTs. You can find many SCR based circuits on the internet.
For triggering the SCR, you can use an opamp based comparator and connect the output of the hall effect sensor to the opamp. Otherwise, it would be difficult to trigger the SCR just with the output of the hall effect sensor.
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0 RobinHart over 3 years ago in reply to rsjawale24

Many thanks. Would an open-collector device trigger the SCR directly ? I have 24 of these circuits to build on a single board and need to keep the physical size small ...
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0 RobinHart over 3 years ago in reply to dougw

The basic concept is for a single LED to light when a magnet is close, then stay on with the magnet removed, the circuit would be unlatched (LED extinguished) with a manual button press.
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0 dougw over 3 years ago in reply to RobinHart

You could try a Hall effect latch such as the ones made by Allegro. A 3 wire chip will sense the magnet and the output will latch and sink 12 mA - which is enough to drive an LED. If you remove the magnet they stay latched. If you reverse the magnet they would turn off, but you don't need to do that. If you remove power with a an NC pushbutton the device will reset to a fault condition (which is off). That is about as simple and compact as possible. Parts numbers include APS12450, APS12400, A1260.
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