Sir FICO
Posts: 29
Joined: Sat Nov 07, 2015 11:34 pm

Help a newbie be smoke free

Fri Nov 18, 2016 5:20 pm

I’ve wired up a DHT22 to my RPi and I’m reading the temp and humidity OK. My next trick is to put the DHT22 on a breadboard for further tinkering.

My Breadboard has its own power supply and I was going to use this to power the DHT22. But then I though, not so fast, I will be wiring the VIn and Ground on the DHT22 from the breadboard power supply, but the data line goes to a RPi pin. A resistor goes between the Vin and the data line.

Of course I’m an electronic ignoramus and I’m wondering if the power supply from the breadboard and the power for the data pin, being from the RPi. would cause something to smoke and go pop. I don't want my to roast my RPi so I’m looking for anyone more clued up to advise me if this is a daft thing to do. I’m looking to be smoke free :-)

Thanks

hippy
Posts: 5760
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Help a newbie be smoke free

Fri Nov 18, 2016 5:26 pm

What is the breadboard voltage which you will be applying to the DHT22 ?

Sir FICO
Posts: 29
Joined: Sat Nov 07, 2015 11:34 pm

Re: Help a newbie be smoke free

Fri Nov 18, 2016 5:38 pm

Hi Hippy, the breadboard power supply can be either 3.3 or 5 volts depending on a jumper setting. I was thinking of using 5v as that is the voltage I used to when wiring directly to the RPi.

hippy
Posts: 5760
Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: Help a newbie be smoke free

Fri Nov 18, 2016 5:48 pm

Use 3V3 and you shouldn't have any problems. You could probably take the 3V3 from the Pi GPIO connector to your breadboard and have even fewer concerns. Remember to connect breadboard 0V to Pi 0V.

Sir FICO
Posts: 29
Joined: Sat Nov 07, 2015 11:34 pm

Re: Help a newbie be smoke free

Fri Nov 18, 2016 6:35 pm

Yes, now I think about it a bit more, though my electronics expertise is extremely lacking, I can see that sharing the ground on the RPi to the ground on the breadboard power supply should enable two power supply positive voltages to be available on one circuit. I think so...... mm. I'm thinking I would stick to either the 3.3 or the 5volts for both. But I will test this on my Zero, less to loose if something gets fried.

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