Yes it’s possible to run them without resistors if you put them all in series and use a current limited power supply. That’s how some LED lighting products do it, just not common LED strips.

Common LED strips are designed for convenience over efficiency. You feed them 12V and you can cut them to any shorter length without worry. You can’t do that as easily with series configurations.

and a constant current supply will suffice for several strips of series LEDs in parallel.

Yes and no. I’ve seen lots of series-parallel products fail with blown LEDs.

For parallel LEDs to work you need three things:

1. Very well matched LEDs.
2. Shared heatsinking, so one LED getting hot shares some of its heat with its neighbours.
3. Reasonable driving level. The more power you put into the LEDs the worse it gets.

These 3 things cost money so they often get skimped.

The LEDs will end up in an autonomous greenhouse where power efficiency is important.

Removing the resistors of a white 12V LED strip will (at best, in theory) increase your efficiency by 25%.

Choosing to use more LEDs and driving them at lower power levels might increase your efficiency even more than this. In 2024 you should be able to get well over 100 lumens per watt, but many LED strips overdrive the LEDs, dramatically lowering their efficiency. LED light output versus power input curves are very nonlinear, you get decreasing returns of light the more power you put in.

autonomous greenhouse

What are you growing? Sounds suspicious. Please don’t do anything illegal.

If your greenhouse is anything larger than a small test then please instead proper fire detection and suppression systems. Don’t get people hurt.

You could probably increase the 82K and 10K resistors to be much bigger (by a factor of 10x or maybe even 100x). Lookup the input impedance for the ADC of your model of ATmega, as long as it’s >10x the size of your resistors then your circuit will probably be accurate enough.

A couple more things to keep in mind:

• a fresh alkaline 9V battery is actually 9.6V or more, not 9V.
• 9V battery voltages droop noticeably when under load because of their high internal resistance. Make sure to measure under the same conditions.

I can’t help but think of the opposite problem. Imagine if a site completely made of bots manages to invite one human and encourages them to invite more humans (via doorstep handshakes or otherwise). Results would be interesting.

This has some similarities to the invite-tree method that lobste.rs uses. You have to convince another, existing user that you’re human to join. If a bot invites lots of other bots it’s easy to tree-ban them all, if a human is repeatedly fallible you can remove their invite privileges, but you still get bots in when they trick humans (lobsters isn’t handshakes-at-doorstep level by any margin).

I convinced another user to invite me over IRC. That’s probably the worst medium for convincing someone that you’re human, but hey, humanity through obscurity :)