Re: "Am I still working okay?" asked the micro controller...

From: Spehro Pefhany (speffSNIP_at_interlogDOTyou.knowwhat)
Date: 05/19/04


Date: Wed, 19 May 2004 18:58:17 GMT

On Wed, 19 May 2004 21:12:52 +0300, the renowned Paul Keinanen
<keinanen@sci.fi> wrote:

>On Wed, 19 May 2004 14:54:55 GMT, CBFalconer <cbfalconer@yahoo.com>
>wrote:
>
>>jiang wrote:
>>>
>>>> One way to check hardware is to run another identical processor
>>>> and compare that they behave the same. If you have three or more
>>>> then you can perform voting so that the most popular answer is
>>>> the one that gets used.
>>>
>>> That is cool idea !..
>>
>>And not so simple. What takes the vote? What if it fails?
>
>Use mechanical or pneumatic voting, not electric.
>
>For instance, if you want to control a bidirectional relay, use a core
>with three separate coils, each controlled by a separate processor. If
>the current in two coils flow in opposite direction, the resultant
>magnetic field is zero. Then the third coil will determine the
>resultant force alone.
>
>Paul

On one machine I'm very familiar with there are three safety
interlocks (one electrical (not electronic), one hydraulic, and one
mechanical). Only when all 3 agree it is safe is the electronics
allowed to do what it wants.

Best regards,
Spehro Pefhany

-- 
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