Need some help with circuit for shuting down the Ordoid

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Need some help with circuit for shuting down the Ordoid

Unread postby alexandros301 » Tue Jan 24, 2017 2:31 am

I'm building a synthesizer with an Odroid-U3 and a Teensy 3.6. I want to be able to shut it down properly (running the "poweroff" command) by using a switch. My idea is to use a stereo on/on switch. On one channel, the middle pin receives the voltage, the pin connecting to the middle pin when the switch is on one position (lets call it the "on" position) connects to the power input of the system, and the other pin (which connects to the middle pin of the switch when it's in the other position - lets call it the "off" position) connects to the common of a relay. The normally open output of the relay also connects to the power input of the whole system.
When I put the switch to the first position, the whole system is being powered up and the relay closes the normally open output. What I want to do is to be able to put the switch in the other position (the one I call the "off" position) and notify the Teensy (by using the other channel of the switch), which will send a signal to the Odroid to power off.

My problem is that when I put the switch in the "off" position the power is being cut off for a very short time, and then it comes back on. The Odroid shuts down forcefully and the "PWR" red LED stays on (perhaps it goes off for a very short time, but I can't see that). Is there some way to avoid this momentary power cutoff? Maybe I need to use a capacitor? Any ideas?

I have attached a crude schematic of the idea (the Teensy connections have been omited for simplicity). Tried to upload it as an image URL from my Google drive, but it doesn't appear...
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power_ctl.pdf
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Re: Need some help with circuit for shuting down the Ordoid

Unread postby odroid » Fri Jan 27, 2017 5:15 am

Even if the red LED is still on, the U3 consumes less than 1~2mA in the power-off state.
So the relay circuit could be removed if you don't care about the red LED light.
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Re: Need some help with circuit for shuting down the Ordoid

Unread postby alexandros301 » Fri Jan 27, 2017 7:33 pm

odroid wrote:Even if the red LED is still on, the U3 consumes less than 1~2mA in the power-off state.
So the relay circuit could be removed if you don't care about the red LED light.

What I need to do is keep the Odroid on when changing the position of the switch. I'm using the relay so cut off the power only when the Odroid has powered off itself. To know when this has happened, I'm using a signal sent to an LED from a sound card that is connected to the Odroid. When I run "poweroff" and the Odroid shuts down, this LED turns off. I'm sending this signal to a Teensy, and when it goes low, the Teensy will open the relay and the power will be cut off.

All this is in theory though, haven't managed to achieve it yet.
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languages_spoken: english
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