Show HN: I turned my iPhone and a $20 smart plug into an f-stop timer

arnarbi | 4 hours ago

Very cool. Is it controlling the plugs via direct Bluetooth connection? Or zigbee via a hub, or wifi (direct or via service)?

I always assumed, probably incorrectly, that there would be too much jitter in the actual timing so I had built a few prototypes of e.g. an esp8266 controlled relay, where you would give the MCU a duration rather than separate on/off commands. But I guess that was wildly over-optimizing. In your case, how stable is the delay from the app sending a command until the switch operates?

I'd add voice mode for color printing in total darkness.

jrflo | 3 hours ago

I was curious about timing accuracy too, has any testing been done on this? Is it accurate to 1s, 0.1s, 0.01s? How dependent is it on the smart switch hardware?

muhehe | 2 hours ago

I played with development photos in a darkroom a long time ago. I don't think one second actually makes much difference.

guax | 49 minutes ago

Depends on how powerful of a light you’re using. 1 second on a 7 second exposure is too much. One second on a 20, not.

alnwlsn | 48 minutes ago

I'd probably put the typical smart switch hardware/software stack at around 0.25 seconds. Maybe you can but I don't think I'd try to rely on anything much faster than that.

If you did, I would go in the custom firmware for the smart switch direction. A lot of them are just an ESP32 inside, and you could probably get to 0.001 seconds that way (but you are switching AC which cycles on the order of 0.02 seconds, so whatever)

sailingcode | 2 hours ago

Good idea. I wonder if the iPhone's camera would be able to measure the projected negative and guide exposure time?

mmmlinux | an hour ago

25$ to unlock all the features...

pimlottc | an hour ago

I get that red-on-black color scheme is a nod to the red lighting of a dark room, but the contrast is so low I can hardly read the example screenshots.

baoooooooooooo | 51 minutes ago

Isn't it more than a nod, and actually a hard requirement to be considered for use in an active darkroom?

It hadn't occurred to me that now with OLEDs you can actually safely limit exposure to wavelengths that would be damaging to the development process - I'd imagine that is what the author is shooting for here

guax | 50 minutes ago

It’s not a nod. It’s required to not ruin the paper during use. A specific yellow would also work but phone screens often output more than just the desired color. Red is the safest.

pimlottc | 37 minutes ago

That's fine, just make the versions on the website readable for people who aren't in a darkroom.

Sarkie | an hour ago

I had no idea what an enlarger was.