1602 LCD backlight LED

1602 LCD display with LED backlight.
1602 LCD display with LED backlight.
1602 LCD display with LED backlight.

The popular TC1602A-01T LCD features an LED backlight. The backlight is nominally 5 V but reading the datasheet gives some warnings.

1602 LCD backlight specification.
1602 LCD backlight specification. Note the caution!

It appears that the LED has a forward voltage, \( V_f \) of 4.1 V at 100 mA but that there is no current limiting built in. If connected directly to a 5 V supply then excessive current would flow (as predicted by the IV curves), the backlight would be destroyed and the display ruined.

A simple LED current limiter will suffice.

1602 LCD backlight current limit and switch.
1602 LCD backlight current limit and switch.

We can calculate the value of R1 from the voltage drop across it and the current through it:

\( R_1 = \frac {V_{SS} – 4.1}{0.1} \)

For a 5 V supply this would give R1 = 9 Ω. The nearest standard value is 10 Ω and this would be fine.

Q1 is a standard NPN switch. If used it will drop about 0.2 V when on and this could be subtracted from the R1 calculation above. If switching is not required then it can be omitted and the LED cathode connected to ground.

Please link to us if you find the information helpful ...<br>Tweet about this on Twitter
Twitter
Share on Facebook
Facebook
Pin on Pinterest
Pinterest
Digg this
Digg
Share on LinkedIn
Linkedin
Share on Reddit
Reddit
Share on StumbleUpon
StumbleUpon
Share on Tumblr
Tumblr