go_away

Author Topic: Magnetic Polarity Indicator  (Read 3012 times)

0 Members and 1 Guest are viewing this topic.

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Magnetic Polarity Indicator
« on: April 19, 2010, 03:03:50 AM »
Bring to your attention a curious device invented by me - an indicator of polarity of the magnet. That inspired me to create it: the construction of my robot with brushless motor from the drive 5,25'' as well as the desire to practice to get acquainted with modern operational amplifiers (current does not require a bipolar power supply, which is very convenient).

Works this device this: when power is on (battery 6F22 9 V) green light. If near the Hall sensor no magnet, the blue and red LEDs do not light.

When approaching the north pole of a magnet to the sensor lights up blue LED

and southern - red.

If you rotate the rotor brushless motor near the sensor, then the blue and red lights alternate, corresponding to passing by the poles of a magnet - it is convenient for determining the number of poles.
Circuit and photo of the PCB - http://www.hexy.name/blog/2010/04/19/magnetic-polarity-indicator/

Offline corrado33

  • Supreme Robot
  • *****
  • Posts: 611
  • Helpful? 11
Re: Magnetic Polarity Indicator
« Reply #1 on: April 19, 2010, 07:16:03 AM »
Hm... that's pretty cool!  Good job!  And welcome to SoR.

Offline z.s.tar.gz

  • Supreme Robot
  • *****
  • Posts: 540
  • Helpful? 5
  • Linux Guru
Re: Magnetic Polarity Indicator
« Reply #2 on: April 19, 2010, 12:26:48 PM »
Very nice. I've always used compasses to check but now I may have to build a little version of my own. (Probably with a 7-segment that says "N" or "S")
Save yourself the typing. Just call me Zach.

Offline chelmi

  • Supreme Robot
  • *****
  • Posts: 496
  • Helpful? 15
Re: Magnetic Polarity Indicator
« Reply #3 on: April 19, 2010, 12:37:52 PM »
Nice!

Could this be used to measure RPM (rotation per minute)?

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Magnetic Polarity Indicator
« Reply #4 on: April 19, 2010, 08:17:16 PM »
Hi,


A small magnet with the North pole painted never runs out of batteries in an ackward moment. ;)
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #5 on: April 20, 2010, 01:19:26 AM »
Could this be used to measure RPM (rotation per minute)?
This requires a pulse counter and a timer (eg, drive 3.5''Hall sensor is used to determine the frequency of rotation - there motor control is carried out not by the sensors, and on backEMF)

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #6 on: April 20, 2010, 01:21:23 AM »
A small magnet with the North pole painted never runs out of batteries in an ackward moment. ;)
English is not my native language, I do not understand your question.
P.S. This is a ferrite magnet, a weak

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #7 on: April 20, 2010, 01:22:48 AM »
However, such devices are sold for $ 39.99  ???
http://www.emovendo.net/magnet/magnet-pole-identifier.html

Offline z.s.tar.gz

  • Supreme Robot
  • *****
  • Posts: 540
  • Helpful? 5
  • Linux Guru
Re: Magnetic Polarity Indicator
« Reply #8 on: April 20, 2010, 05:18:53 AM »
He is saying that painting the north pole red is a much simpler solution that does not require an external circuit.
Save yourself the typing. Just call me Zach.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Magnetic Polarity Indicator
« Reply #9 on: April 20, 2010, 05:32:28 AM »
Hi,

painting the north pole red
How retro... I prefer blue ;D

Actually, some of my "feeler magnets" just have a Sharpie mark, but yes, I find it a bit over-engineered for the purpose.
Some years ago, a guy used a similar circuit for a relative field strength meter to compare magnets, which is a more worthy cause IMO, but I think the OP got his inspiration from the long and very detailed discussion about it, which can be found on some R/C board (don't recall which though).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Magnetic Polarity Indicator
« Reply #10 on: April 20, 2010, 05:51:06 AM »
Hi,

However, such devices are sold for $ 39.99  ???
http://www.emovendo.net/magnet/magnet-pole-identifier.html

At least that one is easy to store in a pocket, but I still don't see any use for it.
We shouldn't produce anything just because we're able to. For an average user shelling out 40 bucks, he'll probably just use it a few times during his life, when the first week(s) of gadget admiration is over.
And when working with magnets, most of the time, you don't care which is N and S, as long as they attract and repel as needed and for that, just use the magnets to tell you that.
Field strength is quite another matter though and you might consider changing your circuit into that.


I don't understand your line "P.S. This is a ferrite magnet, a weak" and even though English isn't my native language either, I don't think that's the reason.

What is a ferrite magnet and what has it to do with my statement?
(And this was my very first question to you, given away by the fact that it's followed by a question mark).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #11 on: April 20, 2010, 07:45:44 AM »

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #12 on: April 20, 2010, 07:48:36 AM »
OP got his inspiration from the long and very detailed discussion about it
No, for this simple circuit i don't need in detailed discussion :)
I thought of  this circuit myself

Offline z.s.tar.gz

  • Supreme Robot
  • *****
  • Posts: 540
  • Helpful? 5
  • Linux Guru
Re: Magnetic Polarity Indicator
« Reply #13 on: April 21, 2010, 11:07:26 AM »
How retro... I prefer blue ;D

I seriously read "red" paint there. I guess I subconsciously associate north with red =P
Save yourself the typing. Just call me Zach.

Offline HexyTopic starter

  • Jr. Member
  • **
  • Posts: 7
  • Helpful? 0
Re: Magnetic Polarity Indicator
« Reply #14 on: April 21, 2010, 12:09:10 PM »

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Magnetic Polarity Indicator
« Reply #15 on: April 23, 2010, 07:24:57 AM »
Hi,

I seriously read "red" paint there. I guess I subconsciously associate north with red =P

Hehe, I know, and here's why:
The poles of our globe is both white, so to differentiate, they called in a psychic who got a mental image of a guy who used to park his car at the north pole:

Hence the red north pole.
(It might have gone down slightly different, but to my defence, I wasn't present  :D)


The South pole is usually white originally, but you may see several other colors.
Traditionally the Horse Shoe magnet was all red (perhaps as a warning or attention getter?) with the polarisation marked in letters (if at all), and then the larger variants got the paint stripped by metal attracted, so soon became blank metal on both the poles and over time, they got around to be produced that way - sometimes with a stamped N and S at the poles.
Later on they have been painted silver or white, when not kept bare metal, probably out of conformalism.
Pot magnets are usually all red, if painted at all.

When I was a kid, the South poles of the magnets I saw was initially black, but later on white came to dominate the South poles.
The use of blue for South poles is probably out of the misconception of color contrast, which likely stems from Goethe's teachings on colors (which was flawed in some places) - blue is comprehended as cold and far away, while red is warm and near according to Goethe.
The actual contrast to red is green and you will see some south poles painted green, but people with some types of color blindness will not be able to tell them apart (and neither will normally sighted people if the lights are down low) - high contrast is the best way of telling them apart, even in low light where the color receptors of the eye don't work (b/w or contrast vision).

And according to a very clever *facepalm* person on Wiki Answers, magnets are all blue:
"On a bar magnet, the south pole is usually colored blue and the north pole is colored south."

Apart from all this trivia, it seem my point were missed. You just need an indication of which end of the magnet is North (or South for that matter), whatever color doesn't matter one tiny bit, as it doesn't take a rocket scientist to figure out the polarity of the unmarked end (well at least if given 3 guesses ;))


As a side note:
I've seen a small handle/holder where a magnet was placed in a sort of gimbal at one end of the handle, to show the precise direction of even fairly week mag fields - might be fun trying to make a similar device - a 3D mag field detector using no power at all.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline z.s.tar.gz

  • Supreme Robot
  • *****
  • Posts: 540
  • Helpful? 5
  • Linux Guru
Re: Magnetic Polarity Indicator
« Reply #16 on: April 23, 2010, 11:27:47 AM »
I've seen a small handle/holder where a magnet was placed in a sort of gimbal at one end of the handle, to show the precise direction of even fairly week mag fields - might be fun trying to make a similar device - a 3D mag field detector using no power at all.

But as Tim "The tool man" Taylor has taught us, more power is more better. Therefor, because that uses no power, it is no better.
Save yourself the typing. Just call me Zach.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Magnetic Polarity Indicator
« Reply #17 on: April 23, 2010, 09:45:39 PM »
Hi,

But as Tim "The tool man" Taylor has taught us, more power is more better. Therefor, because that uses no power, it is no better.
Yeah, I see, we gotta get rid of all the fossile fuels before their expiration date, and Tim is a damn fine character actor that should have had a bunch of Oscars on his mantlepiece, I know, I know  ::)


Does anybody ever watch that show... Or the flicks he's "starring" in?

Well, I have to admit that The Wild Hogs had its moments of floor rolling laughter, but apart from that one, score one for cultural differences, since I just don't get it - the guy is a mess, he only plays Tim, no matter what he's supposed to play and the humor of the show consist mainly of belching, farthing and making primal noises, while being deeply contrascending towards the curvy gender.

It's not really a question about power here, it's about running out of it in an ackward (неуклюжий if Google got it right) moment.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


Get Your Ad Here

data_list