I'm building a simple clock using an ESP8266 chip and a 7 segment LED display which is driven by a HT16K33 chip. The ESP8266 uses 3.3V, the display can handle 5V. I want to use a simple USB cable as a power supply, so I've added a voltage regulator to get the correct voltage.
This all works fine, The problem I have is that the display is flickering when everything is connected to a single power source. During testing I connected the display and the ESP8266 to different power supplies and the flickering was gone. But obviously I don't want to use two USB cables for a single device.
What can I do to prevent the flickering? Since the problem doesn't exist with two power supplies I ruled out a software problem on the ESP8266 (I've written a relatively simple Arduino sketch using existing libraries for a connection to the WiFi, handling the time including NTP and updating the display). The display is updated once a second by the code, but the flickering is distinct higher.
Some more specs, as requested in the comments:
The voltage regulator is an LF33CV (TO220). It outputs up to 500 mA
The ESP8266 module is one of the ESP-01 type. I measured ~70 mA while it is running.
The HT16K33 module is an Adafruit LED Matrix Backpack. It is controlled by the ESP8266 via I2C. It draws around 20mA (including the LEDs).
For the electrolytic capacitor C3 I tried:
- 47 µF
- 100 µF
for the other capacitors C1 and C2:
- 0.01 µF
- 0.1 µF
It is difficult for me to find out what capacitors I need for this.
Both capacitors are as close to the modules as possible on the breadboard.