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What kind of sensor is this ? and how can I use ?

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xmen_xwk

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I found this sensor from old collection(not mine). As far as I remember it is used for RPM count. But what kind of censor is this ? capacitive proximity sensor or inductive ? And how this work, I mean how can I use it for RPM count with an ardiuno ? It has 2 wire connection from backside.

Thank you

imag.jpg
 

deepsetan

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I found this sensor from old collection(not mine). As far as I remember it is used for RPM count. But what kind of censor is this ? capacitive proximity sensor or inductive ? And how this work, I mean how can I use it for RPM count with an ardiuno ? It has 2 wire connection from backside.

Thank you

View attachment 116613

Hi,

From your description, it could be inductive sensor. Inductive sensor with analog output works in similar way as standard 3 wire DC Inductive Sensors. When a metal target comes in vicinity of the sensor , energy is drawn from the oscillator. This energy loss is in proportional with the distance between sensor and the target ;
which is converted in analog signal. The analog signal is made linear and then amplified to give 0-10 V output.
 

xmen_xwk

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There is slight problem with that, the wheel is complete metal with metal teeth. Wont there be a problem if its inductive sensor ?
 

chuckey

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You do not say what colour the wires are. If they are the same colour, then it probablely has a coil inside it. If they are different then the device is polarised, i.e. it can only be connected one way round. If it non polarised then it needs to be followed by a high gain amplifier and would be designed to work by generating a voltage every time a tooth of a cog passed it by (at a small spacing < 1mm?). If it is polarised then it could contain anything including amplifiers schmidt triggers etc.
Frank
 

xmen_xwk

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There is no wire just a female socket.

image2.jpg
 

deepsetan

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Hi,

Actually, inductive sensor sense the presence of metal object (ferrous metal) and non-ferrous metal without touching them. From the link that you attached, I can say that the inductive sensor will detect the metal teeth of the sporcket. The diagram in the link could be a speed sensor. Maybe some of the sensor in this website will help you to understand how inductive sensor work www.festo.com/net/SupportForum/yaf_postst575_Inductive-proximity-sensor-for-speed-sensor.aspx
 
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xmen_xwk

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but will it work with something like that ? and how should I use it ?
 

deepsetan

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but will it work with something like that ? and how should I use it ?

Hi,

For sure it will. There are lot of inductive sensor is used as speed sensor. The speed sensor is exactly the same as the diagram in the link you attached. What do you mean by "how should I use it"?
 

xmen_xwk

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I mean, how do I know how much voltage it require ? Can I use 5V as it will be easier read from arduino. And how do I wire this sensor, there has to be common ground ?

Thank you :)
 

deepsetan

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I mean, how do I know how much voltage it require ? Can I use 5V as it will be easier read from arduino. And how do I wire this sensor, there has to be common ground ?

Thank you :)

Hi,

Generally passive magnetic type inductive speed pickups are used with some signal conditioning (usually comparator type op-amp) and wired to
a digital input as the information you want is the time lapse between pickup pulses which is RPM. The voltage is depends on the sensor. If the voltage is exceed 5V, for sure you can use a relay to make it work. If you can find the datasheet of this component, it will help you to design your circuit.
 

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Hi,

Generally passive magnetic type inductive speed pickups are used with some signal conditioning (usually comparator type op-amp) and wired to
a digital input as the information you want is the time lapse between pickup pulses which is RPM. The voltage is depends on the sensor. If the voltage is exceed 5V, for sure you can use a relay to make it work. If you can find the datasheet of this component, it will help you to design your circuit.

Im trying to use it with LM393P and arduino interrupts, but it failed.

Found this on google.
Untitled.png

I also tested the resistance of sensor, its 3.57K ohm from 2 points. What am I missing ?
 

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Try connecting a capacitor to the output of this circuit and set you DVM to AC volts and try to measure the AC output of the opamp. A toothed wheel must be spun close to the active end of the sensor.
In general you need a fixed magnetic field somewhere, so get a mapping compass and see if you can get a REPULSION somewhere at the active end, if you can only find attraction then there is no magnetic field and an external one must be applied. Waving a magnet around the active end might give you some output.
Frank
 

xmen_xwk

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Currently Im not using on any wheel tooth. I just put metal object back and forth and see if there is any reading in arduino.
 

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It's a reluctance sensor. Inside it is a coil (that's the resistance you can measure) with an iron core that protudes through the end of the casing. As a ferrous object passes close to the end of the core it disturbs the magnetic field inside it and induce a voltage in the coil. It's that voltage you measure. The voltage is proportional to the change in magnetic field, not it's absolute amount so it will not detect the presence of an object, only it's movement and the faster the movement, within limits, the more voltage it will produce. Simply moving an object nearby by hand may not induce enough voltage to be noticed. Typically these things are mounted next to a toothed wheel (or edge of a gear wheel) with a gap of around 1mm and may have hundreds of teeth per second passing by. Even then the signal is usually amplified many times before being usable at logic levels.

A typical application is in ABS systems in cars. There will be one of these behind each of the front wheels (sometimes also back wheels) and a toothed wheel on the axle will rotate with the wheel. There are usually around 25 to 50 teeth around the circumference of the axle so one revolution of the wheel produces that many pulses. The frequency from sensors is compared to ensure the wheels are rotating at the same speed, under skid condition the speeds will be different and a signal is sent to the braking control to counteract the skid.

Brian.
 

xmen_xwk

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Okay, I will test it on wheel teeth. Or maybe use a dc fan to test at home.

Thank you :)
 

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Also note that the LM393 has an open-collector output, you need a pull-up resistor to the Arduino positive supply before it will produce any output.

Brian.
 

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Just another thought. as you need a static magnetic field which you rotating object modifies, you could use the transducer its self. Just arrange for a small fixed DC current to flow through the coil. I would limit the current to less then 5mA. So feed the transducer from a DC source via a current limiting resistor and then try to measure its output.
Frank
 

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I added a 10K pullup resistor to LM393P output. But the program is now stuck, because the interrupt method keep getting called, not loop(). However, now when I stick metal blade to sensor front pin, loop() gets called once(which updates the LCD).

PS : I forgot to mention, the sensor front pin has some kind of magnet. No matter if current flowing or not, its magnetic.

sch.png
 

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