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darrylb123 / usbrelay

Control usb relay - based on hidapi
GNU General Public License v2.0
316 stars 98 forks source link

change initial state? #23

Closed pauledd closed 6 years ago

pauledd commented 6 years ago

Hi

I am not very familiar with the internals of the relay hardware but I am just curious about if it would be possible to modify the relay somehow so that all relays switch to ON on power-up (as default state) even without USB connected, just 12V powering. Is that somehow possible?

darrylb123 commented 6 years ago

The relay contacts are double throw. They have a common with a normally open and normally closed. So you would connect to the common and normally closed to achieve what you want.

On Mon., 23 Jul. 2018, 6:57 pm pauledd, notifications@github.com wrote:

Hi

I am not very familiar with the internals of the relay hardware but I am just curious about if it would be possible to modify the relay somehow so that all relays switch to ON on power-up (as default state) even without USB connected, just 12V powering. Is that somehow possible?

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pauledd commented 6 years ago

That wont work for my purpose... I want to power my Raspberry Pi through the relay, and turn it off as the Raspberry Pi issues a shutdown command. Then to power it on again I want to tip a pushbutton that powers up the relay (just like starting a car) that closes the power switch and stays closed so that the Raspberry Pi can boot up again. So I need the relay to be open if not powered, and closed if powered up (without issuing a usb close command).

20180723_115751

I currently have a startup script that closes the relay on boot, but I have to keep-pressed the switch until the bootscript gets executed (20-30secs...) but I could live with that :)

I originally had the pushbutton and a non-USB relay with low-active characteristics that did the job...

darrylb123 commented 6 years ago

Perhaps an additional timer relay that powers the pi until it can take control.

On Mon., 23 Jul. 2018, 8:07 pm pauledd, notifications@github.com wrote:

That wont work for my purpose... I want to power my Raspberry Pi through the relay, and turn it off as the Raspberry Pi issues a shutdown command. Then to power it on again I want to tip a pushbutton that powers up the relay (just like starting a car) that closes the power switch and stays closed so that the Raspberry Pi can boot up again. So I need the relay to be open if not powered, and closed if powered up (without issuing a usb close command).

[image: 20180723_115751] https://user-images.githubusercontent.com/12088907/43070414-110678a0-8e70-11e8-88ee-dc27cc990bd7.jpg

I currently have a startup script that closes the relay on boot, but I have to keep-pressed the switch until the bootscript gets executed (20-30secs...) but I could live with that :)

I originally had the pushbutton and a non-USB relay with low-active characteristics that did the job... B

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