nijunge
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Relay board is powering my RP

Thu Aug 04, 2022 5:40 am

Hi First a little bacground

Im building a ventilation system and other controlables for a summerhouse, Im an Engineer but fairly new to Rasperry Pi (RP) and not a electrical Engineer ;-).

Im using a 16 relay board (yes the one everyone love to hate on the net I now see) And I got it to work as I want to mostly. I power the whole thing on a off grid solar system with battery backup.

Here is the question on the relay board it recures 5V from the RP but it seems on top of this this 5v connection works both ways so it will actually power the RP via the relay. that means in practise that I need to power board and RP up simultainsly or else it is not stable. (crashes)

I thought about putting a diode in between would that make sense ?

BR Niels

ame
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Re: Relay board is powering my RP

Thu Aug 04, 2022 8:58 am

Post a schematic, or a wiring diagram.
Hmm. What can I put here?

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mahjongg
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Re: Relay board is powering my RP

Thu Aug 04, 2022 10:47 am

start by reading this first: viewtopic.php?f=91&t=83372&p=1225448#p1225448

Make sure that under no condition 5V ends up on a GPIO pin, or you may destroy your PI :!:
Most relay boards are designed to work with an arduino, which has 5V GPIO's, not 3V3 GPIO's.

pcmanbob
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Re: Relay board is powering my RP

Thu Aug 04, 2022 1:41 pm

So what voltage is you 16 way relay board ?

If its 12V then it will have an on board voltage regulator to provide 5V to the control circuit , opto isolators and coil driver control, this is normally only rated at 1A so there will not be sufficient spare current to power the pi from it.

If its 5V powered and you are using an external power supply to power the relay board then it may be possible to power the pi from the same power supply , but its not recommended because if you are switching relay on and off you will voltage fluctuations on the 5V rail which could cause your pi to crash or reboot randomly.

What you should not do is connect both this external 5V and the pi 5V together this cause unexpected currents to flow from one device /power supply to another which could result in damage..

You should only ever connect ground from different power supplies together, to facilitate circuit operation.

If you intend to to use this relay board over a long period you might want to add a pair of ULN2803A chips between the pi gpio and the relay board IN pins to protect the gpio from the 5V on the circuits.
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nijunge
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Joined: Thu Aug 04, 2022 5:30 am

Re: Relay board is powering my RP

Thu Aug 04, 2022 6:38 pm

Thanks for your replys I will make diagram ASAP and post it with details

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