Remove Hall Effect Switch for Push Button Switch - Page 1
Forum section: electronics / beginners

author: money2bills
author_rank: Newbie
timestamp: November 13, 2021, 12:47:49 am
content: I would like to remove a hall effect switch and install a push button switch. The hall effect switch I would like to replace is a two-wire hall effect switch. Currently I have a HAL566 installed and want to remove the sensor. This will enable me to push a button to do what I want.This hall effect switch changes how it behaves in the presence of the magnetic field. The sensor changes the current consumption from below 5mA to about 15mA when the magnetic field is applied and taken away.I have attached the datasheet but am no electrical engineer and am unsure how to recreate this circuit with a push button switch.Can someone help me or teach me how to create a circuit to change the current so precisely with a push button.The hall effect switch is more complex internally and I don't fully understand it.

author: Manul
author_rank: Super Contributor
timestamp: November 13, 2021, 01:53:37 am
content: Quote from: money2bills on November 13, 2021, 12:47:49 amYou don't really need to understand the internal hall switch circuit (although nothing is stopping you from educating yourself). Very likely you also don't need to recreate precise currents. Remember, you just need to trigger the circuit which is triggered by the hall switch. The circuit likely has a single threshold level, lets say 10mA (maybe with slight hysteresis), so current should be either above or bellow to register switch states. 0 - 15mA or 0 - 20mA will likely trigger it. So a switch and a series resistor should do it. Measure voltage when hall switch is removed and calculate resistor to get aproximatelly 15 - 20mA. To get value, divide voltage by current (ohms law). For example, if voltage is 5V you need 250 Ohms resistor to get 20mA (5V / 0.02A). Add this resistor in series with a your button switch and connect in place of hall effect switch. Should work. Although if you use a simple tactile switch and you want to invert action (not sure you want invert or no), you need to make an inverter circuit (so when switch is pressed current is low, released - current high). You can use a transistor for that.Edit: There should also be a current sense resistor in the circuit, so the current will not be exact if you calculate resistor value like decribed above, but the point is that it likely don't need to be precise anyway, just enough to cross the threshold (with some margin). To have more accurate calculation and to know the exact threshold level you would need to look into the circuit. It is also ok to just experiment.If the circuit by any chance have another, low current threshold level used to detect a missing hall sensor or broken wire, then you just need to add one parallel resistor to set constant current level which is not zero (for example 5mA).

author: money2bills
author_rank: Newbie
timestamp: November 13, 2021, 03:32:05 am
content: Manul, first off thank you. I really appreciate the explanation you gave.I will start experimenting and trying to make this circuit. I measured the voltage with the hall effect switch removed and it is 9 volts. You are correct, in order to switch the circuit it just requires over 12mA from what I can find. So for my purposes 15mA should trigger the circuit. When the hall effect switch was installed I measured 0.8 volts at the hall effect switch. I am not sure how to measure the current sense resistor.Very good point about adding a resistor in parallel to send a constant current level just above zero and avoid the circuit from thinking the wire is broken.Thanks again!