Additional SMD elements

Instead of using two AAA (or AA) batteries, you can modify your board to accept Li‑Po or Li‑Ion cells. Also, if you plan to connect to external circuitry that operates on 3.3V levels, it is easy to reconfigure voltage regulator (by default, Glo runs at 2.8V to extend battery life).

On the picture below you can see unpopulated areas of the PCB highlighted where the additional elements need to be soldered (you can click on any of these images for a higher resolution / printable format).

All required elements come included in your DIY kit.

Charging Circuit add-on

Let's start with charging circuit. Perhaps it's best to assemble IC1 and T1 first as they are at the center, while other elements are not in the way:

Now, let's add three 2k resistors:

On the other side of the board there are two LEDs to indicate charging status. Please make sure you are assembling correct positions under the "CHG" text, as there are two more positions for LEDs (USB to serial Tx/Rx indication) next to the headphone jack.

The left LED ("charging") is of amber colour, right one ("done") is blue. Feel free to swap them or use any other colours, but amber and blue is what will be supplied in your DIY kit.

Polarity is indicated by T-shaped pad or green mark, however be careful, the pad of the blue LED is at the cathode while the green mark on the amber LED points towards the cathode. On the photos below you can see correct orientation. The polarity is also possible to figure out by looking at LEDs from the top, if you click & zoom into these photos you will see how cathode is connected to metal base on which the light-emitting crystal is placed, while anode is connected to crystal's top using a golden bonding wire.

Depends how you have the board oriented on your desk, but for convenience I soldered blue LED first...

...and then amber LED.

There are 3 "solder bridges" that need to be closed. One is on bottom side next to the diode which brings 5V from USB to voltage regulator. Normally other two silicone diodes bring enough current and drop the voltage down for regulator to operate safely while standard batteries are connected, but if charging circuit is in place instead, it is desirable to get higher current and less voltage drop from USB via the Schottky diode.

The other two solder bridges are on top side near the edge at lower right corner. You can use a piece of bare wire to connect them if it makes things easier.

Now, time to solder the rechargeable cell wires. Please note that the cell is connected to BAT- and BAT+ pads (as opposed to AAA+ pad where the standard battery holder connects).

Time to test! Charging, and after a few minutes, done (this cell is tiny, and wasn't fully discharged, larger capacity will take more time accordingly).

Finally, you can affix the cell to the board using double-sided tape.

Hope your modification was successful too! :) If you need any help or advice, don't hesitate to contact us.

Reconfiguring for 3.3V operation

If you want to connect external circuits that will not work with 2.8V but require 3.3V, you need to add one resistor to increase regulator's output to desired voltage. This can be done by adding a 1.02M resistor (R3) in parallel with 210k (R2) which results in approximately 174.146 kOhm resistance, following the formula (R2*R3)/(R2+R3).

The regulated voltage is set by the R1 and R2 following the formula: (R1/R2+1)*0.5V. By default, resistors 976 and 210 kOhm as assembled from the factory will result in approximately 2.824V output voltage.

Please note that in respect to the diagram at the top of this article, this picture is upside down: R1 is at the right, while R2/R3 are at the left. You may want to place board this way to have easier access to R2.

The new divider, 976kOhm (R1) and 175.146 kOhm (R2 & R3) will set regulator to output 3.302V. Every of these elements is manufactured within certain tolerances (typically +/-1%) so in practice the result is never exactly as calculated, however setting the voltage this way is precise enough for our purposes.

If you have any questions or suggestions, feel free to discuss on the forum, in the ESP32 Development category.

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