When the camera starts recording, send "HIGH" pulse to a GPIO pin for sunshade retraction?

[loykastj]

I am planning on some sort of servo motor powered sun shade for my Allsky camera to help prevent UV wear on the acrylic in 110 F, hot/sunny days here in Oklahoma.

Would it be possible to have a GPIO pin send a "HIGH" signal when the Allsky software starts to record when the sun is at the preset degrees below the horizon.
The HIGH signal can then be picked up by an Arduino that would interpret that as a button push, which would then have the servo motor rotate 180 degrees to open the sun shade.

[Alex-developer]

Could you not do this now? Something along the lines of

• Get your lat/lon and sunangle from the config files, or given these will change in future releases just hard code them in your own script
• Run the sunwait command to determine if its day or night
• Open or close the shade as appropriate

Happy to throw some code together for you if it will help :-)

I am also curious why the pi is talking to an arduino? Could you not add a servo controller to the pi and drive it that way?

@EricClaeys If we did want to do this in allsky then an option might be to add some other points the module system is called, i.e. day/night transitions and then allow custom modules to handle functions like this? From my point of view its a small addition.

[loykastj]

It sounds easy enough.
Problem for me is I'm learning Arduino at the moment, and I'm just competent enough to use a pull up resistor to detect a HIGH signal from a Pi, then rotate a sunshade using a tiny 5V servo, and reverse the process after another HIGH is sent at the end of the night.
Or I could use an Arduino with a UV light sensor and detect daytime and rotate the cover on/off.

I just don't know enough about Raspberry Pi at this point to drive a servo based on when the camera starts imaging.

[Alex-developer]

You have done the hard bit then :-)

Pretty easy on the pi. You can probably get away with driving a 9g servo directly from the pi but i would never recommend this. I would always use an externally powered controller as there are so many unknowns when driving a servo directly, for example the load on the servo will affect the available power to the pi itself. If you want to try it directly have a look at https://tutorials-raspberrypi.com/raspberry-pi-servo-motor-control/

Its far better to use an externally powered servo controller. Its just a few more wires :-) https://magpi.raspberrypi.com/articles/control-servos-circuitpython-raspberry-pi

When I get a few spare mins I will knock up a sample python script for you to have a play with.