Phone goes to sleep with long timed exposures
When using the timer for very long exposures, the phone can go to sleep if I don't occasionally touch the screen to keep it awake. If possible it would be useful to block the sleep function when using the timer.
By design, if you want to keep the screen active you should adjust your iOS device settings. Note however that this is not necessary as if the device is asleep while the exposure time is active, it will notify the user with an alert before the timer expires.
On my iPhone I can set the phone to never go to sleep. Under brightness/display in settings.
Currently, this is by design. Apple provides no sanctioned way to keep the screen "alive" for apps like ExpoDev. It can be done by using tricks but these come at the expense of battery life and whether Apple's app review team allows them.
ExpoDev tries to be smart about this though - if the device goes to sleep or if you switch to another app while a long exposure timer is running, you will get a pop-up alert notification 30 seconds before the exposure ends that will allow you to jump back to ExpoDev. You have to allow ExpoDev to show notification alerts in your device settings (which is the default unless you change it). This works as long as the exposure is longer than 30 seconds, which should cover most device sleep timeouts.