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# SAC Spinner Electrical Repair - Advice Needed

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On 1/27/2020 at 2:31 PM, ChildOfCv said:

So, now that I've read the paper better, it appears that if the magnetic flux puts an N charge on one leg and an S charge on the other leg, it will work.  If the magnet puts the N/S charge to the sides of the reed switch, or vertically, then no dice.  I'll accept that.

The metals are ferrous, but are not magnets themselves. This means that bringing the magnet near induces a magnetic attraction between the two halves of the switch, and so they clamp together and conduct. You guys are overthinking it... just think "magnet near - closed. Magnet far - open."

At the voltage and current levels inside the SAC, there are not going to be very many restrictions on the device, as long as it's single pole.

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14 minutes ago, Tursi said:

The metals are ferrous, but are not magnets themselves. This means that bringing the magnet near induces a magnetic attraction between the two halves of the switch, and so they clamp together and conduct. You guys are overthinking it... just think "magnet near - closed. Magnet far - open."

Nah, that's the thinking that led me down the eevil path to begin with.  The contacts have a long rectangular cross section, not a circular one.  They can be pulled in one axis, but not in the 90 degree rotated axis without breaking.  The magic that pulls them toward each other when the magnet gets close is that the magnet itself polarizes both contacts in opposite poles, so they are attracted to each other, not necessarily to the magnet.  Alternatively, you only need to polarize one contact, but with a much stronger magnetic field, as seen in the two graphs of closeness vs closed/open when parallel.  If the magnet is perpendicular and centered on the contacts, no amount of closeness will close the contacts.  You must move the magnet towards one leg or the other in order to induce magnetic polarity into one side only.

So in summary, if the magnetic poles are parallel to the contacts, be centered over the contacts.  If they're perpendicular, be off to one side or the other.

It's true that they aren't supposed to be permanent magnets themselves--that would hold their contacts together--but when the magnet comes close, it temporarily magnetizes one or both contacts.  It's possible that the perma-closed switch is that way because it's now a permanent magnet, and degaussing it would fix it.  But that's just speculation on my part.

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Glad your figuring it out Ikranaka

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The Spinner was created in it's present form because of the expense of using an optical based solution.
Also when they designed the SAC Controller they wanted to avoid using batteries for the power supply like the other two controllers.

Paul Jaquays gave a speech with a Q&A stating that he was opposed to the controllers but at least the inventor got to do this...
While sliding his hand across the controller.

Personally I will say that the ADAM was one of the first home computers to have a working mouse.
It may be upside down but that is all a trackball is.
Not only that the SAC Controller 1 spinner is either Horizontal or Vertical while SAC Controller 2 is the opposite.

Paul Jaquays loves to put down the design but in one controller you get true 8 directional movement 16 buttons and a paddle.
Something unheard of at the time.

ADAM is a marvel of engineering and it is a crying shame that it gets so much smack.
The Commodore 64 without it's SID chip is junk and that garbage that came out of Atari could not compare.

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On 1/26/2020 at 12:12 PM, ChildOfCv said:

Switching current doesn't need to be high.  Most likely, any of them will work there.  Same for voltage.  Operating range (AT) is probably the most critical.  Unfortunately, I don't know what the AT rating of the spinner magnets is, but fortunately they're cheap.  Just look for SPST.

A couple of starting suggestions:

Also, make sure to orient them so that the contacts are in the same plane as the magnets when you bend the legs.  If the magnet comes up "beside" the contacts because the switch is laying on its side, it won't activate.

Well I finally ordered and received some replacement reed switches, I went with your suggestions above but ordered two of each available AT range, i.e. 10-15, 15-20 and 20-25.  After some testing and measurement of the new switches against good originals I'd estimate that the originals have an AT rating of around 15.  So, likely that both the 10-15 and 15-20 AT range switches would work in SACs.  I ended up installing the most sensitive ones, i.e. the 10-15 AT range figuring that if these didn't work well then I'd try the next range.  However, after lots of testing and comparison again a working spinner with original reed switches the one with the replacement (10-15 AT) reed switches performed exactly the same.  So looks like that's a good AT range to go with.

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Cool.  I updated the schematic for the SAC with that info.

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8 hours ago, ChildOfCv said:

Cool.  I updated the schematic for the SAC with that info.

Great - is the update available for download?

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