| ??? 01/02/12 15:50 Read: times |
#185260 - Sink or source? Does matter a lot! Responding to: ???'s previous message |
Adam Collins said:
30 years?that's older than me lol. Yeah I agree. And Thanks but can I ask quick unrelated to at89s52 but more to circuits. I used a code to make a LED on P3.0 pin to illuminate every 1 sec it works but with low intensity any way to increase it?( I remember we had to use resistor but what's the value?) You take lots of things for granted - or ignores it - with that question. A LED can be connected in more than one way. Depending on used processor, you'll have different capabilities when LED is connected between + and pin or between pin and ground. Most processors are way better to sink current (i.e. the LED connected with series resistor to VDD) than it is to source current. Only some newer/more advanced 8051 chips have configurations to allow the chip to modify the pin drive logic so it will be able to source current - where the chip internally has a transistor between VDD and the pin. So a traditional 8051 design always sinks current - uses the internal transistor from the pin to ground. Size of resistor? That depends on many things. The amount of current the LED supports. How bright you want the LED (which also includes the efficiency of the LED). But also the maximum currents the processor pin supports. And the maximum power dissipation allowed on the processor port. And the maximum power dissipation on the full processor. |
