Hello Everyone,
I found the forum while investigating how to understand electronic symbols in an electronic circuit that I am puzzled as to how they work in a physical action sense.
Items that may help in the explanation or understanding as to what is going on in my sensors.
I have a three wire Hall Effect sensor with a 5K pull up resistor in front of the NPN transistor that produces an output that I believe starts out as Vcc voltage and then goes to "ground" or zero volts.
The sensor tip has a Hall Effect mechanism in it that is affected by the "South" pole of a magnet. The "Digital output" switches on when the South pole of the magnet is in front of the HE sensor tip and switches off when it moves away.
The HE mechanism I believe is acting as a switch to provide a “saturation voltage low” (I sink = 20 mA) with a maximum voltage of .4 volts.
I believe, but I do not understand how or why this changes the physical path of the voltage/current in the transistor circuit which then changes the output.
The transistor I believe is a three leg NPN transistor, the Base leg I believe is connected to the HE mechanism. Or the HE mechanism is connected to the Base leg of the transistor, not sure if the wording or interaction dictates the flow of voltage or current.
I have a Vcc = either 5 volts DC or 12 volts DC (Two different applications, same sensor)
Note there is always Vcc across pins A and C
My first question, can I test the change or the signal output on pin B with a DMM or do I need an oscilloscope?
I have powered the sensor with a 24 volt capable DC power supply at 5 and 12 volts and I get either Vcc or zero volts across Pins B & C depending on where the magnet is in relationship to the sensor. I believe it is doing something. Note it does the opposite on Pins A & B.
In the sensor diagram there is a 5K resistor that is in parallel to the HE item and the top side of the resistor is connected to Vcc.
This is I believe to be the Collector side of the NPN transistor.
It also has the Pin B (Vout) after the 5K resistor and before the top of the NPN device.
Is the Pin B "output" actually the voltage that is at the Point "C" also referred to as the Collector side of the three-legged transistor?
Is there a way to trace the physical action of the HE sensor/magnet action to see how it acts (either open or closed) and then how that affects the three legs (physical action) of the NPN transistor to understand how the physical path of current and or voltage moves in the circuit? Thus changing the output.
For example does the voltage some how go directly to Pin B say Vcc and then something changes and the voltage out of Pin B goes to Zero volts, how does this physically happen and how does the voltage or current flow change in the line drawing of the circuit?
Is this case where you can label all the items in the circuit and then use electronic formulas to solve for a value at each point in the circuit based on switches opening and closing?
It also does not physically explain how the HE “switch” then affects the transistor in a physical way.
Is this the “Base” leg, does it act as a physical switch some how changing the voltage or current across the collector and emitter?
To make matters more complicated, what if wanted to install a LED which would turn OFF when the South pole of the magnet was in front of the HE tip.
Where physically would it be placed in the circuit and how does the physical path of voltage or current flow then?
Would changing to a PNP transistor make any difference? Is this maybe why one of my four sensors acts differently, three are NPN, one is PNP?
The sensor provides one digital output that is normally OFF and turns ON when a magnetic field is present. The HE switch triggers from the South pole of the magnet.
Note: The output ON means low for an NPN sensor.
Some of this makes sense theoretical sense, but physically or “action” wise does not to me.
My problem is that the sensor seems to be “ON” when I want it “OFF” and vice versa.
I thought if I could physically understand how the action of the three-legged transistor worked I could better trouble shoot how I have the system setup incorrectly.
The other question would be is the actual “output” on pin B actually a voltage signal or is it also just acting like some type of a switch that turns on and off? If it is a "switch" what then does it physically "output"? Is it considered something called a "ground trigger"?
I have no problem purchasing an oscilloscope again no idea what type or capabilities that one would need to test these items.
I have currently four different sensors, three seem to act in the same manner (NPN) and one acts the opposite way (PNP?), just trying to understand how or why this happens.
I really appreciate any help, I have tried spending hours watching videos and reading articles online, the proverbial “Light bulb” in my head will not turn on. I have a new found appreciation of electronics and electrical engineers, it is truly fascinating.
Thank you
Herb
I found the forum while investigating how to understand electronic symbols in an electronic circuit that I am puzzled as to how they work in a physical action sense.
Items that may help in the explanation or understanding as to what is going on in my sensors.
I have a three wire Hall Effect sensor with a 5K pull up resistor in front of the NPN transistor that produces an output that I believe starts out as Vcc voltage and then goes to "ground" or zero volts.
The sensor tip has a Hall Effect mechanism in it that is affected by the "South" pole of a magnet. The "Digital output" switches on when the South pole of the magnet is in front of the HE sensor tip and switches off when it moves away.
The HE mechanism I believe is acting as a switch to provide a “saturation voltage low” (I sink = 20 mA) with a maximum voltage of .4 volts.
I believe, but I do not understand how or why this changes the physical path of the voltage/current in the transistor circuit which then changes the output.
The transistor I believe is a three leg NPN transistor, the Base leg I believe is connected to the HE mechanism. Or the HE mechanism is connected to the Base leg of the transistor, not sure if the wording or interaction dictates the flow of voltage or current.
I have a Vcc = either 5 volts DC or 12 volts DC (Two different applications, same sensor)
Note there is always Vcc across pins A and C
My first question, can I test the change or the signal output on pin B with a DMM or do I need an oscilloscope?
I have powered the sensor with a 24 volt capable DC power supply at 5 and 12 volts and I get either Vcc or zero volts across Pins B & C depending on where the magnet is in relationship to the sensor. I believe it is doing something. Note it does the opposite on Pins A & B.
In the sensor diagram there is a 5K resistor that is in parallel to the HE item and the top side of the resistor is connected to Vcc.
This is I believe to be the Collector side of the NPN transistor.
It also has the Pin B (Vout) after the 5K resistor and before the top of the NPN device.
Is the Pin B "output" actually the voltage that is at the Point "C" also referred to as the Collector side of the three-legged transistor?
Is there a way to trace the physical action of the HE sensor/magnet action to see how it acts (either open or closed) and then how that affects the three legs (physical action) of the NPN transistor to understand how the physical path of current and or voltage moves in the circuit? Thus changing the output.
For example does the voltage some how go directly to Pin B say Vcc and then something changes and the voltage out of Pin B goes to Zero volts, how does this physically happen and how does the voltage or current flow change in the line drawing of the circuit?
Is this case where you can label all the items in the circuit and then use electronic formulas to solve for a value at each point in the circuit based on switches opening and closing?
It also does not physically explain how the HE “switch” then affects the transistor in a physical way.
Is this the “Base” leg, does it act as a physical switch some how changing the voltage or current across the collector and emitter?
To make matters more complicated, what if wanted to install a LED which would turn OFF when the South pole of the magnet was in front of the HE tip.
Where physically would it be placed in the circuit and how does the physical path of voltage or current flow then?
Would changing to a PNP transistor make any difference? Is this maybe why one of my four sensors acts differently, three are NPN, one is PNP?
The sensor provides one digital output that is normally OFF and turns ON when a magnetic field is present. The HE switch triggers from the South pole of the magnet.
Note: The output ON means low for an NPN sensor.
Some of this makes sense theoretical sense, but physically or “action” wise does not to me.
My problem is that the sensor seems to be “ON” when I want it “OFF” and vice versa.
I thought if I could physically understand how the action of the three-legged transistor worked I could better trouble shoot how I have the system setup incorrectly.
The other question would be is the actual “output” on pin B actually a voltage signal or is it also just acting like some type of a switch that turns on and off? If it is a "switch" what then does it physically "output"? Is it considered something called a "ground trigger"?
I have no problem purchasing an oscilloscope again no idea what type or capabilities that one would need to test these items.
I have currently four different sensors, three seem to act in the same manner (NPN) and one acts the opposite way (PNP?), just trying to understand how or why this happens.
I really appreciate any help, I have tried spending hours watching videos and reading articles online, the proverbial “Light bulb” in my head will not turn on. I have a new found appreciation of electronics and electrical engineers, it is truly fascinating.
Thank you
Herb
