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Topic: ABS sensor tester! (Read 565 times) |
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harry.m1byt
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ABS sensor tester!
« on: Jan 11th, 2007, 7:57pm » |
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In the email forum, there has been some discussion of how to test the sensors cheaply. I have not done any research or done any testing on the wheel sensors, but offer the following based upon the information gleaned during the discussion....
The actual sensor seems to be just a coil with a magnet through the centre. As the road wheel turns a cog like wheel rotates in close proximity to the sensor, cutting the magnetic field and thus producing a small pulse of voltage, one pulse for each cog tooth which passes the sensor.
Measuring the resistance of the col is an easy first step in checking the continuity of the coil, but it does not fully prove that the head is working as it should. The resistance should be 1750 Ohms.
To prove the sensor is actually producing the pulses as the wheel turns - really needs the use of an oscilloscope, but these can be expensive and unweildy to use. Alternative ideas for a simple tester have suggested small low voltage bulbs or LED's, but the voltage/current generated seems not to be adequate for these. I therefore offer the following circuit for experimentation...
--o----------o------------------ +12v
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.-. |\| b
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a| | | >- ---
'-' - - |+ / |
| | |/| |V |-> c
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| e | |
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| | | | d
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----o----------o-------o--------- Ground
a= 10 turn 10k preset pot
b= op-amp (not critical but an LM324 should work)
c= LED
d=1k resistor
e = input from one pin of sensor (connect second pin to ground)
I suggest the use of a short bit of the inboard loom with plug from a scrap car is used to connect to the sensor. Idea is to adjust the 10 turn pot to a point where the LED just lights up with a short pulse, as the wheel is slowly turned.
As suggested, the circuit is offered for your experimentaton. I offer no guarantees that i will work. It is just a simple op-amp camparator circuit, If the sensors output voltage rises above a point set by the pot, the LED is turned on.
My apolgies for the poor ASCII drawing, made worse by the proportional font.
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Tompion
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Re: ABS sensor tester!
« Reply #1 on: Jan 12th, 2007, 12:10am » |
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on Jan 11th, 2007, 7:57pm, harry.m1byt wrote:
Measuring the resistance of the col is an easy first step in checking the continuity of the coil, but it does not fully prove that the head is working as it should. The resistance should be 1750 Ohms.
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Hi Harry is that a typo, mine measure about 1050 Ohms,
Uwe on the list wrote 1070 for his.
Dave H
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harry.m1byt
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Re: ABS sensor tester!
« Reply #2 on: Jan 12th, 2007, 3:56pm » |
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on Jan 12th, 2007, 12:10am, Tompion wrote:
Hi Harry is that a typo, mine measure about 1050 Ohms,
Uwe on the list wrote 1070 for his.
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I was working from memory, so quite probably you are correct - I'll ammend it once I have checked further.
1070 or 1050 is within the range of error of measurement and to be expected.
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Octavian_P
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Posts: 1126
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Re: ABS sensor tester!
« Reply #3 on: Jan 27th, 2007, 2:53pm » |
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Here i made this, maybe it will ease off the eyes a bit, I'm not sure about the pinout of the op-am because the program i have used doesn't contain in the library the standard LM circuit
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harry.m1byt
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Re: ABS sensor tester!
« Reply #4 on: Jan 27th, 2007, 3:52pm » |
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Thanks Octavian, nice drawing 
As nothing is critical, you could use any number of single ended supply op amps. The 324 was just one I have used before. It contains four such op amps in the package, only one of which is needed.
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