GPIO Pins all HIGH at boot up

zohsix
New Member

Posts: 8
Raspberry Pi: Yes
Other Device: Arduino

GPIO Pins all HIGH at boot up Mar 6, 2021 7:10:50 GMT -8

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Post by zohsix on Mar 6, 2021 7:10:50 GMT -8

Hello,
I am using the PI2Grover connected to a Grove Relay, set to Normally Open, to one of the digital connectors on the PI2Grover. As soon as I boot up, the relay is CLOSED (GPIO Pin is automatically set to HIGH by the boot process). The problem is that the relay powers a water pump and I don't want the pump running until the program tells it to run, not at boot up.

Is there anyway at boot up that I can set the GPIO output to LOW so that the pump won't run until a program sets the GPIO pin to HIGH?
Regards,
Dan

SDL
Global Moderator

Posts: 5,655
Raspberry Pi: Yes
Other Device: PC, arduino, beagleBone

GPIO Pins all HIGH at boot up Mar 7, 2021 13:31:25 GMT -8

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Post by SDL on Mar 7, 2021 13:31:25 GMT -8

No, by the very nature of the GPIO 3.3V tp 5.0V voltage translation, GPIO lines (which by definition are floating on power up - that can go either way) will wake up as a 1, until initialized and set to 0.

You could put a pulldown resistor to ground(a 1000 Ohm resistor) on the output and that would take it it 0, until it is driven high.

BP

zohsix New Member Posts: 8 Raspberry Pi: Yes Other Device: Arduino	GPIO Pins all HIGH at boot up Mar 9, 2021 2:42:38 GMT -8 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by zohsix on Mar 9, 2021 2:42:38 GMT -8 Thank you, I can try that. The relays I had available are the normally open variety. Could I replace those relays with a normally closed relay? Regards, Dan

SDL Global Moderator Posts: 5,655 Raspberry Pi: Yes Other Device: PC, arduino, beagleBone	GPIO Pins all HIGH at boot up Mar 9, 2021 5:53:17 GMT -8 Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by SDL on Mar 9, 2021 5:53:17 GMT -8 Changing to normally closed would work (If input = 1 keeps the relay open - check). BP

zohsix New Member Posts: 8 Raspberry Pi: Yes Other Device: Arduino	GPIO Pins all HIGH at boot up Mar 13, 2021 10:02:16 GMT -8 SDL likes this Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by zohsix on Mar 13, 2021 10:02:16 GMT -8 Changed the relay to a normally closed and it works perfectly. Regards, Dan

Post by zohsix on Mar 6, 2021 7:10:50 GMT -8

Post by SDL on Mar 7, 2021 13:31:25 GMT -8

Post by zohsix on Mar 9, 2021 2:42:38 GMT -8

Post by SDL on Mar 9, 2021 5:53:17 GMT -8

Post by zohsix on Mar 13, 2021 10:02:16 GMT -8

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