GPIO pin will not hold its output value - Raspberry Pi Forums

i've been raspberry pi user while now, first experience gpio. trying use in simple application command relay board (simple 1:1 gpio-pin-to-relay relationship).

problem gpio pin 27 (bcm mapping) not hold commanded output value.

using python rpi.gpio library, set pin output mode, , command gpio.high. probing pin directly (no relay board attached), see transition high output, hold 20-30 seconds, , transition low. happens when commanding pin via command line using:

code: select all

cd /sys/class/gpio echo 27 > export cd gpio27 echo out > direction echo 1 > value

have 2 rpi's, , tried swapping sd card other board (in suspicion hardware issue), , have same behaviour. i've searched forum , google , found nothing similar problem. or suggestions can offer on here appreciated. irrigation controller project, , every day go without solution this, 1 more more day girlfriend has spend 1.5 hours manually watering our vegetables...

all!

hello, how probe output ?
sure no other programs running working gpio in background ?
, give more details on relais board ? photo, schema, description.

, last not least: p1-13-pin has changed assignment between r1 , r2 of pi. if own device, there no gpio27 on pin p1-13, gpio21.

regards
gerhard

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