Option 1: Dedicated Bi-Directional Logic Level Converter (LLC)
It is recommended to use a dedicated bi-directional LLC for a reliable connection if you are using a 5V Arduino microcontroller. Assuming that you have soldered the header
pins to the logic level converter, you would need to make these connections:
Fingerprint Scanner (Pin #)
Logic Level Converter (Low Side)
Logic Level Converter (High Side)
5V Arduino w/ Atmega328P
UART_TX (3.3V TTL) (Pin 1)
LV1
HV1
RX (pin 4)
UART_RX (3.3V TTL) (Pin 2)
LV4
HV4
TX (pin 5)
GND (Pin 3)
GND
GND
GND
LV
3.3V
Vin (3.3V~6V) (Pin 4)
HV
5V
Note: Make sure to connect 3.3V to the LV side to power the low side of the logic level converters.
After wiring the circuit, it should look like this:
Option 2: Voltage Division w/ 3x 10kOhm Resistors
Otherwise, you could use 3x 10kOhm resistors to divide the voltage from a 5V Arduino down to 3.3V for the fingerprint scanner (FPS) similar to the “Uni-Directional”
application circuit on our old logic level converter as shown below:
Below is the connection between the FPS, 5V Arduino, and resistors for voltage division:
Voltage Divider
Fingerprint Scanner(Pin #)
Voltage Divider
5V Arduino w/ Atmega328P
UART_TX (3.3V TTL) (Pin 1)
RX (pin 4)
GND <-> 10kOhm <-> 10kOhm
UART_RX (3.3V TTL) (Pin 2)
10kOhm
TX (pin 5)
GND
GND (Pin 3)
GND
GND
Vin (3.3V~6V) (Pin 4)
5V
Note: You can add the two 10kOhm resistors in series for 20kOhms.
After wiring the circuit up, it should look like this:
