Ask Electronics

3315 readers

1 users here now

For questions about component-level electronic circuits, tools and equipment.

Rules

1: Be nice.

2: Be on-topic (eg: Electronic, not electrical).

3: No commercial stuff, buying, selling or valuations.

4: Be safe.

founded 1 year ago

MODERATORS

[email protected]

Simple light-sensitive light switch? (feddit.org)

submitted 3 months ago by [email protected] to c/[email protected]

11 comments fedilink hide all child comments

I'm trying to build a very simple, stupid light switch for my grow light. Essentially, I want to turn on the light, if it gets too dark outside, so that my plants can survive the northern winter.

Since I'm a software guy, my first thought was an ESP32, but that seems excessive.

My current approach would be something like this: https://www.ebay.com/itm/313561010352 In conjunction with a relay, both powered by a USB-PSU.

If the light level is low enough, the logic DO pin should send a signal and that should be enough to trigger a small relay, so that the relay then closes the circuit to switch on the lights.

Is that idea completely stupid? With electronics, I'm usually missing something very obvious.

The lights themselves are already just usb powered and only draw 5W, so that shouldn't be problem.

What I'm concerned with is the actual switching. Is the logic signal "strong" enough to activate a relay? Would simple transistor maybe sufficient?

you are viewing a single comment's thread
view the rest of the comments

[–] litchralee 2 points 3 months ago

If you're looking to do this project without a microcontroller -- it's an exercise that every SW engineer should consider doing at least once -- then the venerable 555 timer may be of aid here:

https://elonics.org/light-sensor-circuit-using-ldr-555-timer-adjustable/