Skip to content

09/01/2013

Arduino & ESP8266 stuff

R2 determines the current.
Calculations:
– LED current is approximately equal to: 0.5 / R2
– R3 power: the power dissipated by the resistor is approximately: 0.25 / R2.
choose a resistor value at least 2x the power calculated so the resistor does not get burning hot. so for 700mA LED current: R2 = 0.5 / 0.7 = 0.71 ohms. closest standard resistor is 0.75 ohms. R2 power = 0.25 / 0.71 = 0.35 watts. we’ll need at least a 1/2 watt rated resistor.
led-driver3

The design of this LED driver is very simple and probably can be found in many variations on the interenet: T2 operates in linear mode and acts as a variable resistor that controls the current through the LED’s. R1 pulls-up the gate of T2 so that T2 starts up in its conductive state.
As the current begins to flow through the LED’s, T2, and R2…

View original post 1,356 more words

Advertisements

From → Uncategorized

Leave a Comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: