Chief Delphi - Hall Effect Sensors

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Chief Delphi (http://www.chiefdelphi.com/forums/index.php)

- Technical Discussion (http://www.chiefdelphi.com/forums/forumdisplay.php?f=22)

- - Hall Effect Sensors (http://www.chiefdelphi.com/forums/showthread.php?t=111375)

electroken

01-02-2013 18:15

Re: Hall Effect Sensors

Quote:

Originally Posted by BitTwiddler (Post 1225995)

Nice find! A few questions.
1. Where did you purchase them?
2. Did you wire them with the bypass and lowpass capacitors?
3. Do you have any data on how it performs on chain sprocket teeth?

1. Digi-Key (hurry... only 22,000 left!)
2. The capacitor hiding in the epoxy is a 0.1uF 50V ceramic across power and ground.
3. We haven't tried reading sprocket teeth, but I would expect them to work well with steel sprockets and a small air gap.

electroken

01-02-2013 18:17

Re: Hall Effect Sensors

Quote:

Originally Posted by Ether (Post 1225921)

How are you decoding the signal?

That's a good question. I told the student writing the code what to expect for a signal, and he said "Yeah, I got this".

Ether

01-02-2013 18:32

Re: Hall Effect Sensors

Quote:

Originally Posted by electroken (Post 1226084)

That's a good question. I told the student writing the code what to expect for a signal, and he said "Yeah, I got this".

The decoding method makes a big difference in the quality of the signal, especially at high speeds (depending in the method used).

Could you ask him to join the discussion here?

MrForbes

01-02-2013 22:49

Re: Hall Effect Sensors

Quote:

Originally Posted by BitTwiddler (Post 1226074)

I think Jim was yanking my chain (also non-ferrous) for not being more specific.

It was a serious question, Dave, because the sprocket is aluminum and I thought they only worked on ferrous teeth.

carneeki

02-02-2013 04:23

Re: Hall Effect Sensors

Quote:

Originally Posted by Katna.Grace (Post 1225732)

When mounting them, make sure that the sensor itself can't move, so that it can't be sheared off by whatever it's measuring or drift away from the magnet.

Hi Katherine,

We (FRC #4774) are going to use the same sensor boards! Thanks for making them open for others :D

We (FRC #3132) *1 forgot to include the value of T1 on the schematic. It is a 2N2222 NPN transistor, a TO92 package. Part of me is wondering if we can make all components sit flat so the board could be laminated in a future revision?

BR,

Adam

*1 (Yes, I am a mentor for two teams) :)

Oldbikerider

02-02-2013 18:13

Re: Hall Effect Sensors

Quote:

Originally Posted by carneeki (Post 1226288)

We (FRC #4774) are going to use the same sensor boards! Thanks for making them open for others :D

Hi Adam, we've just ordered magnets from a company in Sydney: http://www.magnet.com.au/neodymium_r...ts#discs_small

If I'd known that you were going to use the same sensors I'd have ordered enough for 4774 as well. We may have extras, so let us know if you need some.

Of course, as you know, DealExtreme also ship neo magnets to Australia.

fovea1959

14-02-2013 13:37

Re: Hall Effect Sensors

Team 2729 also is selling some boards they designed and made that are quite nice and that wire right up to the sidecar with a PWM cable; proceeds fund their team. See http://www.chiefdelphi.com/forums/sh...2&postcount=14.

We glue a small diametrically magnetized ring magnet (K&J Magnetics R424DIA) on the back shaft of a BaneBots motor to drive it, 'tis robust. See http://www.chiefdelphi.com/forums/sh...d.php?t=112294

philso

14-02-2013 14:10

Re: Hall Effect Sensors

Quote:

Originally Posted by electroken (Post 1225905)

A useful gear tooth sensor that wires directly into a digital input is the Allegro Microsystems ATS667LSG. We like to use them when we need speed information but not direction information and we don't need the highest resolution. We also like that they're $6.

In the photo below an ATS667LSG is mounted to a carrier board and installed in the side of a Cim-u-lator gearbox, with its face about 0.03" from the output gear. It gives us a nice, clean 27 pulses per output shaft revolution. The sensor on top of the right motor is just posing for the photo.

Electrotoken, am I right in thinking that the magnets in the hall effect sensor in the ATS667LSG detects the disturbances in the fields from the magnets mounted in the sensor package as the steel gears in the gearbox rotates through the field? Did you just connect it into one of the digital inputs on the Digital Sidecar? The datasheet does not seem to show any sort of calibration. Did you just stick it on, connect the wires and run?

electroken

14-02-2013 15:03

Re: Hall Effect Sensors

Quote:

Originally Posted by philso (Post 1233342)

Your thinking is correct in that the magnet is buried in the sensor. I don't know if the 0.1uF cap I have between power and ground at the sensor end is strictly required, but it makes me feel better.

It really is as simple as wiring into the digital sidecar and counting pulses. We used two of these last year and will be using three this year.

jwakeman

19-02-2013 14:33

Re: Hall Effect Sensors

Quote:

Originally Posted by Gregor (Post 1216883)

We used the hall effect sensor in your second link last year, combined with a 22 tooth steel sprocket on our shooter, with no issues.

Do you know if you were able to sense direction with this sensor?

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