What Can I Use to Replace a Hall Effect Switch?

Thread Starter

money2bills

Joined Nov 3, 2019
10
I am trying to create a circuit to lock my doors. There are currently two hall effect sensors/switches (A3161) that activate the door lock actuators with the turn of the key.

Does anyone here know what I can replace the hall sensors with that can be triggered electronically?
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
I need a component that can provide 15 to 20 mA when supplied with a ground signal preferably. The circuit is about 0.3 to 0.8 volts. When at rest or idle provides zero or nearly zero milliamps.

Thank you for any help.
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
Yes, the key turns a plastic barrel that has magnets installed in it. When I turn the key the magnet is moved away from the sensor and it allows a small amount of current to flow.
 

Marcus2012

Joined Feb 22, 2015
425
Gotcha, sorry to ask again, but what's the context here. By that I mean, what's undesirable about it's current functionality and why does it need to be changed? You have a few options for alternative mechanisms but you are somewhat limited if you require no mechanical connection between the barrel and the sensor (a lever etc.). These tend to be sensors that detect changes in things in flux, such as magnetic/electric fields (HE - magnetic/electronic, reed switch - magnetic/mechanical) and EM(visible light, microwaves etc) sources. As is the lock has been engineered for a HE sensor any alternatives are limited while you're having to immitate the output of the HE sensor. Some other members probably have some more insight here than me tbh.
 

crutschow

Joined Mar 14, 2008
34,285
I need a component that can provide 15 to 20 mA when supplied with a ground signal preferably. The circuit is about 0.3 to 0.8 volts. When at rest or idle provides zero or nearly zero milliamps.
That is not at all clear.
What is 0.3V to 0.8V?
What exactly is the signal you want to generate?

So are you asking for a circuit that can operate the locks in parallel with the Hall-effect devices?
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
I am attempting to reproduce a circuit in my 2005 BMW X3. I installed a remote start into my vehicle and the lock and unlock did not work with the remote start. So I am trying to reproduce the circuit so that I can place it into a small enclosure to pulse the lock and unlock to signal the general module to lock and unlock all the doors.

The circuit I am trying to reproduce uses two hall effect sensors (A3161E), I have attached the datasheet. I have also included an image of the circuit.


20191103_230434.jpg


A simplified version is drawn below.


20191103_230908.jpg


When idle the two hall effect sensors have a magnet over both of them. When the key turns clockwise to lock, one hall effect is uncovered and when turned counter clockwise the other hall effect sensor is uncovered.

I thought I could reproduce this circuit without hall effect sensors and just use two transistors, couple diodes, and relays if needed. I could use some advice if anyone here could help me make it so the negative (ground) trigger from the remote start will trigger either lock or unlock.

If there is more information I can provide that can help please let me know what I can find out for you.

I am trying to find an oscilloscope to see what is happening better and more visually but need to find one still.

The hall effect sensors are soldered onto the board in a two wire configuration so only a power/signal wire and ground wire are present for each hall effect sensor.

When I check the voltage of each power/signal wire I have 0.8 volts when plugged into the switch. When the wire is not attached to the switch there is about 9.0 volts at the wire. I tested each wire when the key was turned and the lowest the voltage dropped was to 0.730-0.750 volts. Wierd part is both lock and unlock wires voltage change. I dont know why this happens. I assume it is the magnetic field is effecting both.

The remote start instructions adviced me that a negative signal would trigger the circuit to work. So I tried to just attach a negative ground to each lock and unlock but that did not work.

I have determined to lock and unlock the vehicle that both hall effect sensors must show a signal to the lock module. I tested the circuit with another lock actuator and attached only one hall sensor and the ground. When tested it didn't lock or unlock the vehicle. When each wire for the two hall sensors and a ground were used the lock and unlock worked properly.

I measured the current draw for each and they were extremely low. The lock circuit pulled 0.45 mA and the unlock circuit pulled 0.44mA. It did not matter if the it was locked or unlocked they were both showing change in amperage. When at rest/idle the meter showed 0.01 mA for both lock and unlock circuits.

Below are simplified drawings showing the magnet (seen in yellow) at different positions.

Rest Position:

20191103_233550.jpg


Lock Position:

20191103_233952.jpg


Unlock Position:

20191103_234007.jpg





Thank you to anyone able to help me and I will try to help as much as possible.
 

Marcus2012

Joined Feb 22, 2015
425
Hey sorry for the late reply on this, busy weekend :)

So by the looks of it each HE sensor is pulling a lock or unlock signal wire to ground when the magnetic is removed. But just to check the entire yellow bit is magnetic right? The simplest way to replicate this would be to use a transistor in parallel with each HE sensor that could also pull the signal to ground (btw ground isn't always 0V, it can be higher, especially in cars). You can test this though if you can bridge the wires momentarily while active (be careful!!). Did the remote start kit only have one I/O control port for the locking? Some cars share one signal line for lock/unlock while others require seperate ones the differentiate direction as turning the key again the same way can have an alternate function (such as disabling alarm sensors) in addition to the extra security it provides.
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
Thank you for the help. The entire yellow bit is the magnet.

Each hall sensor has one wire for the signal that goes to the lock module and they share a ground that goes to the chassis. So there is a total of only three wires.

I tested the voltage and current of each wire. I cut the wires between hall sensor and lock module and cut the ground wire to measure current between each.

I went out and bought a new amp meter to measure the milliamp draw on each.

When Idle:
Lock Hall Sensor Wire: 0.10 mA
Unlock Hall Sensor Wire: 0.10 mA
Shared Ground Wire: 0.21 mA

When locked:
Lock Hall Sensor Wire: 0.45 mA
Unlock Hall Sensor Wire: 0.44 mA
Share Ground Wire: 0.90 mA

When Unlocked:
Lock Hall Sensor Wire: 0.45 mA
Unlock Hall Sensor Wire: 0.44 mA
Share Ground Wire: 0.90 mA

The confusing part to me is there was no measurable difference between the lock or unlock, maybe it is timing.

I know that only one hall sensor should go to ground when the key is turned but both hall sensors appear to be affected. They have diodes to prevent any reverse flow of current as I understand from the datasheet.

I am open to trying some ideas. I have tried in parallel to the circuit to activate the lock wire several different ways:

-Directly Grounding Wire
-Grounding with Zener Diode
-Grounding with Schottky Diode
-Grounding with Varying Resistors
-Grounding with 3mm LED
-Grounding with 3mm LED and Zener Diode
-Grounding with 3mm LED and Schottky Diode
-Grounding with 3mm LED, Resistor and Schottky Diode
-Grounding with 3mm LED, Resistor, Zener Diode and Schottky Diode

I have been unable to make it lock or unlock without rotating the drum. The key does not need to present, I can rotate it manually and it still works.

The remote start has two wires one for lock and one for unlock that provides a 500mA negative signal.

Can you explain more in detail what it is to bridge the wires when active?

Thank you again for the help and I appreciate the advice.
 

Marcus2012

Joined Feb 22, 2015
425
Ok this is looking a lot more complicated and after looking at the datasheet I think I may know why.

"These devices are normally operated in a 2-wire mode, where the supply
terminal and the output terminal are tied together. An external comparator
detects the change in total supply current by the addition (output off, B > BOP)
or subtraction (output on, B < BRP) of IOUT."


The afterrmarket remote start system you installed, how many wires does that have marked for use with this lock?
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
The remote start only has two wires for the purpose of the lock.

Remote Start Door Lock Wires:
Blue Wire - 500mA (-) Unlock Output
Green Wire - 500mA (-) Lock Output

Remote Start also has Factory Alarm Arm/Disarm Wires that can be used:
Black/White Wire - 200mA (-) Factory Alarm Disarm Output
Green/White Wire - 200mA (-) Factory Alarm Arm Output
 

dendad

Joined Feb 20, 2016
4,451
One problem is at least one of the Hall sensors will be operated, switched to 0V, so having another switch in parallel with that one will not work.
How about a servo to move the magnets?
 

Marcus2012

Joined Feb 22, 2015
425
Have you tried connecting the remote start door lock wires to their respective wires and also attaching the remaining ground wire to the ground on the remote start unit?
 

Thread Starter

money2bills

Joined Nov 3, 2019
10
A servo may be an option if I can not figure this out with simple components. I would need a servo to rotate the barrel 45° clockwise or counterclockwise and then back to 0°. If you know of a 12 volt servo that can do this please let me know.

I have now tried grounding both vehicles lock and unlock wires with resistors and diodes at the same time, also with different resistance and nothing worked. I have tried with the remote start wires but no response from the locking system either.

I matched the voltage drop and still no response. Do the hall sensors do anything special that I am not understanding?
 
Top