external power supply for relay

[sylvain15]

hello everyone,

i've got a problem with raspberry , gpio and a relay.

i choose an external power supply 5v for a little relay board. Relay will be command by gpio 23.

The relay didnt commute when i asked it when it is powered by external power supply but works when it is powered by 5v raspberry gpio.

I test with a voltmeter and 5v is correctly the delivered by external power supply and relay's red del is brightful.
I tried another power supply without good result.

ive got the same matter with a wireless 433 PT2262 board which work with raspberry 5v and not with external power supply.

is there any configuration to modify to allow gpio pin working without using the 5v, or the ground of the rpi ?

thanks for your advice,

Sylvain

PS: iove got the same configuration (other rpi but same relay) at home and it works perfectly... i really dont unterstand why its not working here ! i'm stuck :-S

[Gert van Loo]

Did you connect the ground of the external supply to the ground of the Pi?

[sylvain15]

no. there is only the gpio plug on the raspberry nothing else.

i should plug power supply ground to rpi ground ?

[drgeoff]

no. there is only the gpio plug on the raspberry nothing else.

i should plug power supply ground to rpi ground ?

Yes you must join the grounds (negatives) of the RPi PSU and the external PSU.

[FLYFISH TECHNOLOGIES]

Hi,

i should plug power supply ground to rpi ground ?

By default.

Even the simplest battery has two terminals. If you'd like to get some power from it, you must connect both terminals.
This principle is applicable to all kind of electrical circuits - when you add a power supply, you must connect its both terminals somehow/somewhere. Connecting grounds together is to be the first item on your list of possibilities...


Best wishes, Ivan Zilic.

[sylvain15]

yes it works !

thants a lot