Electronics help.

MinniMe_2

Hi All hope this in the right place....

I'm I have just started looking into electronics and need to design a circuit that lights an LED when a signal (from another board) is high. I'm having one of those days and just can't do it.

any ideas or good websites to look at?

cheers:o

SamC_4

It sounds like you just want a LED driver circuit like the ones shown here. Generally Bowden's Hobby Circuits is good, as is Make blog.

MinniMe_2

Thanks SamC,

am i being really simple or can I simply connect the signal to the LED and if the signal is high it will light the LED?

thanks

SamC_4

MinniMe wrote:

am i being really simple or can I simply connect the signal to the LED and if the signal is high it will light the LED?
thanks

It depends on the output power of the circuit that's producing the signal. If it's powerful enough then all you will need is a resistor in series with the LED to drop the voltage to the right level (see handy calculator here). If you don't use a resistor your LED will burn out.

If the circuit doesn't have enough power output to drive a LED you'll need a LED driver circuit.

Joe_Bloggs

You will have to limit the current through the LED to stop it from damaging itself or whatever powers it, if driven from a voltage source. A resistor in series of a few hundred to 1000 Ohms should do the job. A rough estimation would be that the LED has two volts accross it when turned on hence the series resistor would have 5-2 = 3 volts accross it if a high is 5V. The current through the LED would be 3/(resistor chosen).
J_B.

MinniMe_2

SamC and Joe_Bloggs

thank you both so much (you have made my day!) Signal coming in is 5V so has no problem driving LED and as I am using LED's with integrated resistors I think this is gonna work:)

I'm so happy - also means If I acn get the schematic drawn up asap I won't be here until all hours this evening!

thanks again