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| Adding an LED power indicator to vintage circuit |
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| gkmaia:
I would like to add an LED to a vintage circuit as an indicator it is powered on. My plan would be to add on a 12v rail that comes out of T1 pins 9 and 10. Add a couple resistor as a voltage divider to bring the voltage down. By my calculations I will get about 2.04v at the LED with the divider. Can someone with more experience let me know if its a good plan? Or any drawbacks of my idea with some viable suggestions? |
| StillTrying:
"My plan would be to add on a 12v rail that comes out of T1 pins 9 and 10." There's already a LED there, or is that the one you've added. SuperBright LEDs are bright enough as an indicator at 2 or 3 mA, so you can connect them almost anywhere there's DC. "Add a couple resistor as a voltage divider" A LED only needs one series current limiting resistor. The polarity of C104, C105 and D107 look the wrong way around to me. |
| gkmaia:
The LED you see is the one I added. That rail runs 12v. My LED runs 2.5v. Without a divider I may end up burning it or not? Yes, they were wrong. Just fixed it thanks. |
| Benta:
You mention that is's vintage eq. In that case, I'd install a neon lamp across the 240 V line (don't forget a series resistor). Much easier. |
| pwlps:
--- Quote from: gkmaia on May 18, 2019, 09:18:31 am ---That rail runs 12v. My LED runs 2.5v. Without a divider I may end up burning it or not? --- End quote --- A LED is a diode: you drive it with a constant current, not voltage. Just put a resistor in series, for example to get 10mA it will be (12V-2.5V)/10mA that is around 1k. |
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