Rob,

> Gentleman, please!
> I never thought that my initial post would cause so much ruckus
> as you Yanks say.

Don't worry about that, it was not your doing.   While mark triggered it
with his joke, the following "ruckus" is all my doing (my apologies if that
bothered you).

But jeez, what a simple "can you explain how that reasoning is faulty ?" can
result in ...

Regards,
Rudy Wieser





"RobH"  wrote in message
news:fod9dbFnapeU1@mid.individual.net...
> On 13/06/18 20:19, Dennis Lee Bieber wrote:
>> On Wed, 13 Jun 2018 19:41:02 +0100, druck  declaimed
>> the
>> following:
>>
>>> If you measure between 2 pins and get 0V it /could/ mean they are at the
>>> same potential, or it could mean there is *NO* connection between them.
>>> That's why you always measure from the common ground to the pin.
>>>
>>
>> We presume the board is not broken -- thereby all pins do have a shared
>> common ground level, and a voltmeter connected between any two pins
>> should
>> report the potential (voltage) difference between those two pins, doesn't
>> matter what the voltage relative to ground is. Basically, which ever pin
>> has the voltmeter /black/ (using standard convention for voltmeters)
>> /defines/ "ground level", and the /red/ lead will report the potential
>> difference from "ground level".
>>
>>> Ground to 5V should give 5V
>>> Ground to GPIO set high should give 3.3V
>>
>> Note: unless I misunderstood the situation gravely, the GPIO is being
>> used as an INPUT and it is the motion sensor/detector that is setting the
>> pin value. That sensor is powered by the 5V system, which is why we have
>> the concern that if it is putting 5V on the GPIO, it could be causing
>> damage to the pin circuits.
>>
>>> 5V to GPIO should give 0V because they aren't connected.
>>
>> But they are connected -- by the RPi common ground. If groundGPIO can
>> be measured and ground5V can be measured, and both are not 0V, then the
>> differential between 5VGPIO can also be measured directly -- one pin
>> becomes the effective "ground" and the other will present a voltage
>> relative to the other.
>>
>> Yes, if groundGPIO shows 0V it could mean the pin is really at ground
>> level (and the differential between it and 5V is still valid), or the pin
>> is physically isolated from the rest of the circuit in which case it will
>> never register any non-0V and you might as well toss that pin into the
>> trash.
>> .
>>>
>>> ---druck
>>
>>
>
> Gentleman, please!
> I never thought that my initial post would cause so much ruckus as you
> Yanks say.
>
> I post the link for the tutorial I followed and hoped that some of you
> would have viewed it to clear up any anomalys I may have made with my
> initial post.
>
> Again as I posted earlier, it was the crappy £5 ebay camera which was the
> fault/problem and not the sensor at all.
>

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