Smart bookcase with plant monitor + LED (pt. 2)


I made a post 2 months ago asking about the type of board to use and summarising the functions I want to do for a school project. If you want to check it out here is the link: Smart bookcase with plant monitor + LED

I’ve made some good progress since then. After choosing the Firebeetle ESP32-E because of its appropriateness to my project, I have successfully learnt how to control the LED lights from the Blynk app. Here is also an updated circuit diagram:

I now have two separate questions.

Q. 1
As I am going to be putting these electronics within a bookcase, I just want to know about how well power travels over a distance.

For example, I am planning a 90cm tall bookcase and the easiest way to hide the microcontroller unit is at the very bottom. I am also planning to have 3 LED strips with one being at the very top. This would mean that power would have to travel from the base to the top (around 90cm). For testing I have been using prototyping wires, these to be exact:

Unfortunately the jumper wires are a bit short so I need a better solution. What wires can I use for longer lengths and will I have any problems with this distance in terms of powering the LEDs?

Q. 2
Within the bookcase I also have 2 moisture sensors which use I2C communication with the microcontroller. The moisure sensors I am using are the Adafruit STEMMA Soil Sensor:

I think that by default the sensors have the same address value so I can’t use both at the same time without a change. Do I need to solder the AD0 jumper on one of these to change its address by one (Pinouts | Adafruit STEMMA Soil Sensor - I2C Capacitive Moisture Sensor | Adafruit Learning System)? I think that’s right but just want to make sure before I do any soldering.

Thanks for your help,


Hi Isabel,

Awesome project, I’m keen to see it finished :smiley:

DC power transmits fairly well, at 90 cm you shouldn’t have any worries. I’ll attach some links below on how you could figure out some numbers.
Instead of the power, you might actually run into some issues getting the data signal up there!
Using a logic level converter you can bring the data voltage from 3.3V from the ESP32 to 5V which should help with transmission (you should be good at 90cm though!)

If you have a Bunnings or electrical good store around I’d say the most accessible option would be some mains power cable, where you have the GND, Data and Voltage pins from the LED strip already in the right order.

Yeah, you’ll have to solder the A0 jumper, once you have the new address will be 0x37.

Calculating the voltage drop across a transmission line

Using this calculator you can plug in some approximate values:

The power cables will have a parasitic resistance, then overestimating the current (1A for 0.5m of LED strip) flowing through the wire will let you calculate the voltage drop and hence the power lost!

Keen to see more!

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