 | | Re: Homemade LED Bricks
|
|
David Johnston <lego-robotics@crynwr.com> wrote in message news:LOBBJCENKNHFLCK...inet.ie... (...) I'd say 330 Ohm 1/4 Watt. (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
(...) Er, 330 ohm may be ok for the usual transistor type circuit where the nominal supply voltage is 5 volt, if my memory has not failed me. It may be a bit low, I think, for the RCX where the nominal voltage is 9 volts which is almost double of 5 (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
basicly.. it's i*r=v where i = current in amps and r = resistance in ohms and v = voltage in volts.. so.. If we want to find out the resistor's value.. we re arrange it like so.. r = v/i so 10 millamps (typical led current) = .01 Amps.. And at 9 (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
grrr.. I flubbed.. instead of r = .01/9 make it r = 9/.01 ----- Original Message ----- From: Keith Miller <kmiller@talon.net> To: <lego-robotics@crynwr.com> Sent: Thursday, November 11, 1999 10:23 PM Subject: Re: Homemade LED Bricks (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
(...) Thanks for the enlightenment. I remembered it went something like that. But don't you have to allow for the forward voltage drop across the LED, typically 1.6 volt (still from memory)? That is, the voltage should be 9 - 1.6 = 7.4 volts. So the (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
Keith Miller writes: > basicly.. it's i*r=v where i = current in amps and r = resistance in ohms > and v = voltage in volts.. > so.. > If we want to find out the resistor's value.. we re arrange it like so.. > r = v/i > so 10 millamps (typical led (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
Russell Nelson <lego-robotics@crynwr.com> wrote in message news:14380.1027.3890...nwr.com... (...) Its not .7 volts for an LED its more like 1.8volts and its takes 20ma if you want for full brightness for a typical display LED. (or more for a (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
| |
| | Re: Homemade LED Bricks
|
|
(...) The forward voltage of the LED does depend on the colour. In an electronics catalogue, the following values are listed, but do vary for specific devices. Red typically 2v Yellow 2.1v Green 2.2v Blue 3.3v White 3.6v ///// < .. > > - (...) (25 years ago, 12-Nov-99, to lugnet.robotics)
|
