IOT the USB Grow Lights

Details

I ordered a set of inexpensive ($20) grow lights in early 2020 for some supplemental lighting for a few succulents. The lights worked for intended purpose but had some annoying features like always on or flashing bright blue LEDs and the on/off timer needed to be reactivated every time power was interrupted. Reactivation had to occur at the time when you wanted the lights to turn on.

In early 2022 the controls stopped working the lights. A quick inspection didn't identify anything obviously wrong with the unit so a similar replacement was ordered. The lights sat on the work bench inching closer to an eternity in one of my junk bins but were spared by this project.

Replacing the damaged control board and eliminating the annoying features is the objective of this project. The replacement lights had a similar control board but the physical case was redesigned. I designed the a replacement PCB to fit either enclosure. I ordered a few more different varieties of these USB powered grow lights. Unfortunately seems like the new control box with RGB indicator lights are much smaller and will not work my redesigned board. (At least not without 3d printing a replacement case too.)

The replacement PCB uses and ESP8266 module which just fits inside the case. The factory boards had option to control 6 different channels of outputs so this was replicated. The 5V input power has a linear regulator for 3.3V power for the ESP with some protection features added for good measure.

For the software side of things, ESPHome is perfectly suited to IOT these grow lights. Proof of concept ESPHome configuration allows all of the button inputs to accessed in home assistant and PWM output of each LED channel controlled. My test unit has been running the original set of lights for 2 weeks now controlled by an automation routine in home assistant.

Project Logs

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Rev 2 Built
mulcmu • 07/30/2022 at 02:08 • 0 comments

I built up 4 of the Rev 2 boards. I've been using up a 5 year old tube of solder paste by adding some fresh flux and mixing it up on the stencil before spreading. This round turned out a bit thin and spread out a bit too much on some of the pads. A bunch of tombstones and misaligned SOT-23 after reflow.
The voltage supervisors was still causing some issues. The 3.3V regulators on 2 of the boards were in the 3.25 range and that wasn't enough to satisfy the supervisor so the ESP was held in reset. I ended up removing them and boards worked fine, for future builds getting a 3.2V or 3.15V threshold supervisor.
An unpopulated Rev 1 PCB was used to make a generic bed of nails adapter for a programing fixture. It worked well enough for programming a few by hand.
The replacement grow light was upgraded with a Rev 2 board. The PCB fit in the alternate style case with one modification to clip a plastic standoff interfering with the ESP shield. The Rev 2 boards used a 2A poly fuse and this light was built using a 2A barrel jack with corresponding pigtail to connect with the control box.
Lack of LED on the board makes troubleshooting difficult and the user feedback seems to be missing. The only unused pin is the TX line which could be utilized for some feedback, just not one that is always on and light up a dark room bright.
Rev 1 Testing
mulcmu • 07/02/2022 at 01:02 • 0 comments

The Rev 1 PCB with the voltage supervisor and pull up resistor changes from rev 2 tested fine using a small perf-board LED setup with USB power. ESPHome configuration was created and installed. The ESP8266 would connect to wifi only on the first attempt. Subsequent reboots of the ESP8266 would try to establish connection with router but would never succeed until router was rebooted. This was annoying and seems to be an issue with the DHCP configuration. Setting the ESPHome board to a static IP address seems to be an adequate work around.

The breakout board was removed and the real lights were installed. They would work for a while sporadically and then turn off. Troubleshooting identified the 500mA poly-fuse was tripping. I tested one of the light bulbs and it used 900mA at 5V. Testing the stock controller showed that the duty cycle was limited to about 15%. The poly fuse was replaced with a pin header to short the pads. Test board was connected to bench power supply and the duty cycle was adjusted to get current draw of about 700mA between both lights. An old 5V 700mA phone charger was cannibalized to finish the assembly for more software development.

Test software posted on github.
Rev 2 PCB
mulcmu • 06/28/2022 at 20:52 • 0 comments

Rev 2 of the PCB fixes reset issue.
Posted in Github repository.
Rev 1 PCB
mulcmu • 06/24/2022 at 14:44 • 0 comments

Revision 1 PCB was designed to fit inside the existing control enclosure for the lights. The ESP-WROOM would fit in the enclosure but needed some offset cuts in the PCB. A similar set of lights had the same controls but the plastic molding was different to retain the board in place. The PCB should fit either of these two style cases.

Ordered 5 prototype PCB from jlcpcb and stencil from oshstencil. The assembly went okay despite the solder paste going on a bit messy.

Initial testing went okay. The board kept resetting due to lack of pull-up on the reset line. The voltage supervisor was removed during the troubleshooting. Rev 2 in progress to add the pull-up resistor. Might change the supervisor to 3.3V too.

Arduino test code loaded on okay to test the lights and buttons. Took a good bit of searching to find the INPUT_PULLDOWN_16 to enable the pulldown on GPIO16.

Next step to get rev 2 PCB on order and start working on ESPHome configuration to properly IOT it into home assistant.