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Looking for sensor suggestions

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As to the height you may want to consider the use of a string pot, yo yo pot or draw wire sensor (they have a dozen names :) ). What I am getting at can be seen here. They are marketed by several companies. Looking at your initial pictures they may fit into the scheme of things as to an accurate indication of the height of the dropping mechanism above the dash pot. A relatively small one with an analog output would likely work well for your application.

As to the release something you need to note is the signal you use for a start. Since this operation happens pretty quick the start and stop signals need to be pretty accurate. For example if a relay controls the magnet just looking at or using the relay contacts to drive something to get your signal may lie to you. Relay contact open times need considered when dealing with milliseconds. I believe using a hall effect device is the best way to go about it as it should provide the most accurate start time.

Ron
 
Ya i was wondering the discrepancy between when the "signal" for the release happens and the magnetic actually dropping the object. The only problem about using a sensor for the start time is, the object will be dropping from different heights.

Do you think if i mounted the sensor on the magnetic it self would generate a lot of noise? I was thinking what if mount the sensor on the magnetic then use a comparator circuit to detect when the magnetic is engaged/disengaged.

I'll look into the draw wire sensor thanks for the info ! :D

Thanks for the responses as always!
 
I thought about this a little yesterday. I have a small AC electro magnet that was left over from a prototype project of years ago. I placed a small hall sensor close to it and it activated the sensor. I noticed that when power was removed my steel dowel did hang on to the magnet, I don't know how long. However, it did seem to release the instant the LED on my hall effect went out.

I wanted to experiment a little more but yesterday we had an unexpected death on my little street so we gave the family time and everything got screwed up as to my plans. Maybe after work today I can post a few pictures of what I am getting at with all this.

Ron
 
Ah no worries take your time. I'm looking into a combination of the ideas that have been presented so far.

I have quick question, try not to side track the thread so far. wondering if any one knows or can suggest a place to inquire to purchase an array of IR sensor say, like 20-25 sensor in a single strip with a space of .5 cm in between each sensor. Basically a manufacture that produce "array sensors".

Thanks!
 
OK, thanks for the PM and memory wake up. :)

Based on the experiment I previously posted I concluded that the rod does not begin to drop when power is instantly removed from the electro magnet. That led me to believe that using a hall sensor to detect when the field collapses is likely the best way to go as a start command for timing. I also experimented with an accelerometer for the stop using a magnetic base on the accelerometer and that seemed to work.

As to the hall effect sensor I used some I had lying around from Allegro that years ago I got through Allied Electronics. The one I used is no longer in production and I don't believe Allied still carries Allegro. A Honeywell version should work. Something like these from Allegro. At a few bucks each buy a few and experiment.

As to height measurement I would suggest using a string pot as I suggested earlier. Since it has been awhile I don't know where I put that magnet down. I know it is around here somewhere. :)

I could do some pictures if you think it would help.

Ron
 
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