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P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 12:51 pm

On GPIO Pins,
P1-01, does it provide 3.3volts or we input 3.3volts ?

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mahjongg
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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 12:56 pm

any of the the GPIO's can be programmed to behave like an output to say in your words to "provide 3.3V", (or 0V depending on whether you output a 1" or a "0") OR it can be an input that can accept a voltage, generally spoken a voltage below a low threshold will be seen as a "0" and above another higher threshold it will be seen as a "1" (in the "forbidden zone" between the two thresholds what the PI sees is undefined).

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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 12:59 pm

mahjongg wrote:any of the the GPIO's can be programmed to behave like an output to say in your words to "provide 3.3V", (or 0V depending on whether you output a 1" or a "0") OR it can be an input that can accept a voltage, generally spoken a voltage below a low threshold will be seen as a "0" and above another higher threshold it will be seen as a "1" (in the "forbidden zone" between the two thresholds what the PI sees is undefined).

Hello, Thank you for your response,
In this tutorial,
http://www.cl.cam.ac.uk/projects/raspbe ... mperature/

They say that you are supposed to connect Pin 3 of the Sensor to the 3V3 of GPIO , So I connected the Pin 3 of my Temperature Sensor to the Pin 1 of GPIO.
Does this GPIO pin1 will provide 3.3 Volts to my Temperature Sensor ?

Where am I suppose to apply 0 or 1 to make it act like an Input or Output ?

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jojopi
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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 1:08 pm

P1-01 is the 3V3 output from the regulator RG2. You can use it to power an external circuit, as long as it needs no more than about 50mA.

Generally speaking, you cannot supply 3V3 into P1-01, because the board requires 5V as well. (But it has been reported that, if you do not need any external USB devices, you can tie the 5V and 3V3 rails together and feed in 3V3.)

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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 1:23 pm

Pin 1 on the RPi header is a full time 3V3 power source. It not a programmable GPIO. This is connected to the power pin on the sensor.

The DATA pin of the sensor is connected to a GPIO4. That GPIO pin is configured by the program shown in your link.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

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mahjongg
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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Oct 26, 2013 7:15 pm

(But it has been reported that, if you do not need any external USB devices, you can tie the 5V and 3V3 rails together and feed in 3V3.)
:o :o :o Scary! you are describing a very good way to "let the smoke out of your PI", that is to utterly destroy it!

Never connect the 3V3 and 5V pins of the GPIO header together, it will destroy your PI if you then put 5V on your PI.

And no, the PI itself (the SoC) does use 5V! Its used by its internal switching regulator that makes a variable internal core voltage. Also the 3V3 regulator doesn't like it when it gets 3V3 on its output, with nothing at its 5V input, it might get damaged that way, so don't simply put 3V3 on the 3V3 input, and nothing on the 5V input.

Just perhaps the 5V input of the SoC will work with 3V3, but its very scary stuff to connect 5V and 3V3 together, so be extremely careful when you try! its not something I would recommend an unexperienced user to try.

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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Sat Nov 02, 2013 11:23 pm

On this post I think we are dealing with
To many IF or BUTS and nothing
Permanent, Lets use the Pi what
It was design for, Learning programming
And electronics It will be far safer to input
the correct power supply. Build a few electronic
circuits then design the programme for them
Then if they don't work ,you will have a better
Idea how to fix it More rewarding to see your
Own designs working
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Mon Feb 29, 2016 7:37 am

mahjongg wrote:Never connect the 3V3 and 5V pins of the GPIO header together, it will destroy your PI if you then put 5V on your PI.
So let's say that I was just an utter NOOB and I did just that. I connected 5V to the 3V3 pin and now my Raspberry Pi 2 won't turn on. No LED's, nothing. All that happens is the IC labelled U3 gets really hot. Does the Pi need this component to work? And if so, how can I go about replacing it? I would hate to have to do that. It's so dang tiny.

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rurwin
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Re: P1-01, does it provide 3.3volts or we input 3.3volts

Mon Feb 29, 2016 7:44 am

You need to find somewhere that has a supply of magic smoke. Any company that manufactures electronics should keep a stock and many of them have SMD rework stations with magnifying glasses and other kit for replacing defective parts. If you ask very, very nicely they may be able to help you especially if you find their rework engineer in the local pub and make it worth their while to give up a lunch-hour.

There's also a good chance that U3 is not the only component you destroyed and you need to decide when you give up and pay another £35 for a new Pi.

In my experience (this was in the days of RPi 1 though) the Pi will not run on less than 4.6V, so I don't believe it could ever run with only 3.3V

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