Posts: 1
Joined: Sun Nov 25, 2018 10:17 pm

Power Bank operated Music Box

Sun Nov 25, 2018 11:14 pm

Dear all,
I'm working on a power bank powered music box, based around a raspberry pi zero.

It should have several buttons, an on/off switch and a volume encoder.
Screenshot from 2018-11-25 23-19-10.png
Power Supply Interface
Screenshot from 2018-11-25 23-19-10.png (15.19 KiB) Viewed 1152 times
As you can see in the first schematic, I planned to use external pull ups resistor (10k) for all inputs, but I think I will omit all of them and configure each input pin with an internal pull up. This part should be fine and I don't expect any big issues with it.

The main struggle I have is related to the power supply. As soon as the raspberry zero is halted, it should disconnect from the power bank.
An idea could be as following:
The attachment Screenshot from 2018-11-25 23-19-10.png is no longer available
The 5V line is connected to the raspberry pi zero via a double coil latch relays.
As soon as the main switch is turned on, it generates a pulse to set the relays and closes the 5V > the raspberry gets power and starts.
It reads (GPIO16 as Input)in the main switch and initiates

Code: Select all

sudo shutdown -h now
when the main switch is open for a certain amount of time. The NC7SZ08 serves as level shifter 5V to 3.3V.

GPIO12 will be configured as gpio-poweroff high
Name: gpio-poweroff
Info: Drives a GPIO high or low on poweroff (including halt)
This should slowly charge the 1uF compensator. About 10sec later the voltage is enough to activate the reset coil of the relays and disconnects the 5V line.

Unfortunately I don't have an electronic lab/equipment at home, so I can't really test it beforehand. What do you think about my approach?
Screenshot from 2018-11-25 23-27-31.png
Input Interface
Screenshot from 2018-11-25 23-27-31.png (34.39 KiB) Viewed 1152 times

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