How to design circuit for Hall Effect North pole magnet field for TURN ON of circuit?? (not off)

Thread Starter

russwr

Joined Aug 29, 2017
66
Hall Effect types sensors as unipolar, bipolar and linear, with 3 or 4 pins, work with 2 poles magnets, but not seem to turn on as a switch on type with north pole magnet to TURN ON an electrical load. Any ideas? Bipolar or unipolar? I need to send 4 amps DC 12v through a 3 ohm resistor in series with small .2ohm load coil when a North pole magnet enters the area. The tiny Hall pre mounted on small board could have it's long leads bent U shaped, so that the head of the Hall is backwards facing to the passing North magnet. An N channel MOSFET circuit would handle current flow if the Hall could turn on the gate properly, and also shut off the main power automatically, after the magnet passes by.

Statement found - A Hall effect "switch type "will turn on in the presence of south magnetic field on its face or north magnetic field on the OPPOSITE side. It will turn off when the magnet is removed.
A Hall effect "latch type design" works like a switch, but will stay on when the magnet is removed. It will turn off if the north pole is applied to the face or the power is turned off.
 
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MisterBill2

Joined Jan 23, 2018
19,053
The very first step will be to verify that the applied magnetic field is actually making the switch change states. That can be done using a multimeter connected between the sensor output and the supply common lead.
 

sghioto

Joined Dec 31, 2017
5,421
Any ideas? Bipolar or unipolar? I need to send 4 amps DC 12v through a 3 ohm resistor in series with small .2ohm load coil when a North pole magnet enters the area.
Using a SS49E Hall sensor might be one solution.
From the performance chart you can see the output from the SS49E is appx 1/2 supply voltage with no magnetic field present.
A strong negative field from a North pole magnet will reduce the output voltage sufficient to activate the 555 thus turning on the mosfet.
Vr1 is set to 2.35 volts at pin #5 and activates the 555 when the voltage drops to appx 1.15 volts.
1713994560670.png
 

MisterBill2

Joined Jan 23, 2018
19,053
Repeating a requirement with no additional information is not really helpful. And having a 3 ohm resistor in series with a 0.2 ohm load does not tell us very much , either. Is the load a solenoid? or what? Inductive loads require additional considerations under some conditions.
 

Thread Starter

russwr

Joined Aug 29, 2017
66
Repeating a requirement with no additional information is not really helpful. And having a 3 ohm resistor in series with a 0.2 ohm load does not tell us very much , either. Is the load a solenoid? or what? Inductive loads require additional considerations under some conditions.
Circuit is to superimpose 12 volts through 3 ohms to pass through .2ohm wire coil primary, So as 4 amps passes instead of the usual 3 amps at 5-8volts. No other way to do it.
 
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