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Hi, Mike. Assuming there have been no other physical changes, the only other "quick fix" I can think of is degaussing the mounting bracket or whatever is being used to keep the sensor in place. Sometimes that will cause this problem, and it can be accentuated by the positioning of the mounting bracket relative to the sensor.
You could always try plastic, too. Good luck, and sorry for your troubles. Chris
Built a tachometer transducer using a Hall Effect sensor. Has worked well many years but now is failing. Have discovered that the Hall Effect sensor tends to "stick" on, even when no magnetic field around, as long as power is on.
On the assumption it's not the hysteresis circuit inside the device, I tried degaussing the sensor. No success so far. Anyone ever heard of this happening before and anyone got a fix? Could make a new transducer with a new part, but the whole thing is potted in epoxy. If there's an easy fix, would like to try that first.
Thanks,
Mike Palmer < Excellence in Ergonomics
Yup, i have seen it happen., replace the component.
On 29 Jan 2005 05:10:43 GMT, snipped-for-privacy@aol.comnet.org (MikeremlaP) wroth:
There is no easy fix. Hall sensors are a cross between electronic ICs and microminiature mechanical devices. The whole thing is very sensitive to heat and physical stress on the package. I suspect that the sensor has degraded and is now effectively "dead".
Potting compounds, especially simple epoxys meant for adhesive purposes, can generate enormous strain on IC packages especially when combined with heat cycles.
When (not if) you rebuild the assembly, take care to either use potting compounds meant expressly for sensitive electronics or use a flexible buffer coat over the hall sensor before potting the entire assembly.
Jim
Sounds like a bad Sensor. However last "Sample Changer " I serviced , was "acting up" intermittantly, and was restored to service after I wiped away some metallic dust on the Hall-Effect Sensor. Hall-effect Sensor, instead of an Opto-electronic Sensor to avoid dust problems !! Just made the problem worse !! hmm!
Yukio YANO
You may want to double check the type of sensor you have. Some are made to latch on, and be turned off with the other poll of a magnet.
Also, you may check to be sure that you do not have excessive current through the device. Sometimes, this can cause a device to latch up.
You may also check to be sure that the strength of the magnet is not to powerful to damage the sensor. Some mfg. do not like to see excessive magnetic fields.
The third thing may try to place a 0.1 uF cap across the power leads as close to the sensor as possible. Sometimes, a sensor will misbehave without this.
Whiskerstherat
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