I was thinking about creating an internal LED to indicate when a ][+ or //e is powered up on the workbench. I just want something clearly reminding me to turn it off before I start connecting or disconnecting stuff. I anticipate using it with the case off and few cards installed. I was thinking I could just use jumper hook connectors to connect to +5v and GND pins on a chip (or some other source) to a red LED and insulate with heat shrink but that might lead to careless connection errors. It might make more sense to just use a A2 prototyping board and just plug it into any slot and tie the LED to +5 and GND from the slot.
Where would you hook up the jumper solution to minimize errors?
Do I really even need a resistor on this?
Do I really even need a resistor on this?
YES! Unless you find an LED with an internal resistor.
The //e already has such an LED on the motherboard. It is back near the power connector. And yes, you usually need a resistor on an LED if the power source has any amount of juice or it will pop, even on 5V.
Thanks.
I mostly work on ][+s and clones and had forgotten the //e already had a light. So the obvious place to connect it is to the pins used for the Power light already there, easy to find and hard to confuse, fixed connector - DUH. Or is that +12v? Guess I'd need to do a little looking things up now...
So just a 470 ohm resistor on the positive leg of the LED?
That should work. It can go on either leg.
Thank you.
jeffmazur is correct that it doesn't really matter which leg. The value isn't super critical as long as it is enough to drop the current enough to keep from frying the LED but not so much as to make it too dim. Varying the resistor some within that range will change the brightness. So like you could probably get away with as low as a 330 Ohm to a 560 Ohm, maybe a 680 Ohm and it would probably still work but the brghtness would change. Varying the current is more fun of course on a color LED which has 4 pins (ground, R, G, B). You can change the color that way.
I would go with the exact same schematic as the Apple IIe. I think it's smart:
PowerLED.png