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TKS

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I have a Inductive sensor wich depending on speed changes the resistance is this right?

Wich simple, small circuit do i need to make the alternating singnal go digital? sow the microcontroller can measure the pulses?

I tried to make it work with a transistor but looks like when putting 0,4 volts on the gate there are 0,5 on the pic.

When i adjust the 2nd adjustable resistor wich is in series with the sensor.
Then the voltage on the input pin increases

Sow my situation is: How to make
an smitt trigger input, or how to convert some analog signals to digital ones?? am i done when i use the ST (smitt trigger) inputs my pic cpu has???

What i have tried is to Put the sensor in series with a pot.
I calculated that the value from the pot should be 7500ohms, because my sensor gives 1000ohm in rest, 1100 when slowturning anyway its difficult to measure.


Regards,

Tks
 
Please post a schematic. I can't tell what is going on from your description.
 
TKS said:
I have a Inductive sensor wich depending on speed changes the resistance is this right?

I wouldn't have thought so?. Inductive sensors are usually just a coil that detects a magnet passing by it, just like a dynamo or alternator. So the output is a sinewave, the frequency of which varies with the speed of rotation.

Wich simple, small circuit do i need to make the alternating singnal go digital? sow the microcontroller can measure the pulses?

I tried to make it work with a transistor but looks like when putting 0,4 volts on the gate there are 0,5 on the pic.

When i adjust the 2nd adjustable resistor wich is in series with the sensor.
Then the voltage on the input pin increases

Sow my situation is: How to make
an smitt trigger input, or how to convert some analog signals to digital ones?? am i done when i use the ST (smitt trigger) inputs my pic cpu has???

What i have tried is to Put the sensor in series with a pot.
I calculated that the value from the pot should be 7500ohms, because my sensor gives 1000ohm in rest, 1100 when slowturning anyway its difficult to measure.

That sounds completely wrong!. First you need to determine if your sensor has internal electronics, does it have power to it?. If so, you then need to use a scope on the output to see what the signal is like - if it's a decent size sinewave then a simple schmitt trigger is all you need. Or you could even just feed it through a resistor to the base of an unbiased transistor?.
 
mhh

Hi Nigel!,

thanxs for your reply!

The type of sensor i got is offcourse automotive and its a ABS sensor.
It works inductive i guess, have 2 spare ones, sow will try one,

but what i remember indeed it had allot of thine wire rounded up round an piece of metal.

Sow if i untherstand it, i only need to take voltage from it right??
How to hook it up??

The axle's in de car have a ring with many teeth.

Will try to make again my scope remember??
And look a bit at the voltage, hope its fast enough..

What is a unbiased transistor??
is it a transistor wich only conducts after the 0,6volts and is closed before the 0,6 limit (or another value)??

Regards,

Tks
 
Re: mhh

TKS said:
What is a unbiased transistor??
is it a transistor wich only conducts after the 0,6volts and is closed before the 0,6 limit (or another value)??

Just a transistor with a resistor from base to emitter, but NO resistor to +ve. It's switched ON by the incoming signal on positive peaks.
 
Ok,

Do i still need to connect the input pin to GND with 10K resistor?
even if i use the ST inputs??

1K is that enough to connect the base to the Emitter?

Sow if i have the 2 wires from the coil,

i put 2 diodes on it? or what do i do with that part?

Then the voltage coming out of it will be DC, then i put a 1K From the base to the emitter(???? not collector???) , and from the emitter to the input pin??

I cant untherstand wy to the emitter and not to the collector?

BC547 is that the one i need???(NPN)

Maybe i will just try hooking it up directly, the currents will be made smaller by an resistance...


Could it work??

I have to put an resistor because i imagine on high turning speeds the voltage could rise high right??

Tks
 
Re: Ok,

TKS said:
Do i still need to connect the input pin to GND with 10K resistor?
even if i use the ST inputs??

1K is that enough to connect the base to the Emitter?

Sow if i have the 2 wires from the coil,

i put 2 diodes on it? or what do i do with that part?

Then the voltage coming out of it will be DC, then i put a 1K From the base to the emitter(???? not collector???) , and from the emitter to the input pin??

I cant untherstand wy to the emitter and not to the collector?

BC547 is that the one i need???(NPN)

Maybe i will just try hooking it up directly, the currents will be made smaller by an resistance...


Could it work??

I have to put an resistor because i imagine on high turning speeds the voltage could rise high right??

Tks

1) Is the sensor JUST a coil, no electronics.

2) What is the output level of the coil?.

3) You may be able to connect the coil through a simple series resistor directly to a PIC pin, nothing else required!.
 
Ok,

Will determine first you question before asking more,

anyway, here is a circuit i drawnup to test if i untherstanded you,
 

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Nigel

I have measured with my multimeter.

I cant measure any DC voltage on the sensor.
The sensor don't has electronics inside, only a coil with a magnet.
(have pics if you want).

The 2 wires i have are the 2 from the coil.

If i turn the wheel as fast as i can, i can measure 0,2 vac probaly while driveing even more.

The good news is that if i turn it slow i also measure voltage but offcourse allot less!

What to do?

Shall i just make the Transistor setup? looks like its the best option right?
Is the vac signal a problem?

What about the ST input?? (smitt trigger)?? is it needed in both setups?
its recommened right??
 
Re: Nigel

TKS said:
I have measured with my multimeter.

I cant measure any DC voltage on the sensor.
The sensor don't has electronics inside, only a coil with a magnet.
(have pics if you want).

You won't be able to measure it with a meter, on either AC or DC, you need a scope!.

The 2 wires i have are the 2 from the coil.

If i turn the wheel as fast as i can, i can measure 0,2 vac probaly while driveing even more.

The good news is that if i turn it slow i also measure voltage but offcourse allot less!

What to do?

Shall i just make the Transistor setup? looks like its the best option right?
Is the vac signal a problem?

The AC is the whole point, you're trying to measure it's frequency.

I would still suggest scoping the signal, to find out how big it is, then you will know if you have to amplify or not!.

What about the ST input?? (smitt trigger)?? is it needed in both setups?
its recommened right??

It's probably a good idea to use a schmitt input, particularly as they are available.
 
The problem is nigel

that i don't have a scope,

do you think that the ADC of a pic can measure the signal???

and how would be the test bench???

i mean one wire from the sensor to ground and the other to the pic ANALOG input???

or should i try it with a analog meter? the one i have isn't very good
sow probaly also isn't fast??
 
With an inductive trigger sensor for the cars engine, I use a LM1815 to read it. I don't think this helps you though, without knowing more about your ABS sensor.

It's odd that this is a straight inductive sensor. Usually ABS wheel sensors give a square wave signal.
 
well...

mhh...

This is the picture..

the upper bar you see is in the coil and its a permanent magnet, i think that the pulse coming from the coil is to short to be noticed by the multimeter.

the abs ring has allot of teeth and there are also very small sow think that is the problem for the multimeter.

Tks
 

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Nigel in you sheme i need some values,

i know that they will depend on the coil output,

but i have to try something right???

alos where do i need to put some pots to be able to adjust everything??

i mean to say to search for the setting??

In your T2 scheme i would like to take for R2 = 1K R4 10K and R3 4,2K

the NPN will be an BC547c do you think it should work????

also if the voltage is lower then 0,6 what to do??

Tks
 
TKS said:
Nigel in you sheme i need some values,

i know that they will depend on the coil output,

but i have to try something right???

alos where do i need to put some pots to be able to adjust everything??

i mean to say to search for the setting??

In your T2 scheme i would like to take for R2 = 1K R4 10K and R3 4,2K

the NPN will be an BC547c do you think it should work????

They sound reasonable values to try, you might increase R2 to 10K, there's no need for it to be so low. A BC547 is fine.

also if the voltage is lower then 0,6 what to do??

Amplify the signal first!.
 
Yeah

i could smell that solution, but i ask it to know how i could do it??

Tks

I have tried to connect a led to the sensor but it doesn't light up..

(not visible for the eye at least...:D:D)

Tks
 
Re: Yeah

TKS said:
i could smell that solution, but i ask it to know how i could do it??

[/quote[

With an amplifier - sorry, but it's true! - either use an opamp or a discrete amplifier. But again, you need to know what's coming out of the sensor, you can't get anywhere completely blind!.

I have tried to connect a led to the sensor but it doesn't light up..

(not visible for the eye at least...:D:D)

I wouldn't have expected it to.
 
ok nigel,

i will go out and buy an osciloscope or have you got anny better idea???

i could just buy another sensor right? but the oscilioscope will be more usefull right??

Tks
 
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