Can anyone recommend a panel indicator... it could be LED or Neon bulb, or incandescent.... I've only used LEDs and only for small voltages, so I'm not sure what to use here
I need 2 panel indicators, one needs to run off of 120V and one off of
28V.... someone mentioned for me to try neon bulbs... so far I haven't had much luck on the web, I'm trying to get as low power light as I can, they don't have to be very big... anything the size of a standard LED or maybe up to as big as a penny would be fine... bigger than that would be too big... it's just a panel indicator
Use a neon bulb, like the ol' reliable NE2, with about 120K in series, for the 120VAC. I believe they'll work on DC, but only one electrode will light. For 28VDC, use a plain ordinary LED with the appropriate series resistor, R = (Vsupply - Vled) / .01A.
:Can anyone recommend a panel indicator... it could be LED or Neon :bulb, or incandescent.... I've only used LEDs and only for small :voltages, so I'm not sure what to use here : :I need 2 panel indicators, one needs to run off of 120V and one off of :28V.... someone mentioned for me to try neon bulbs... so far I haven't :had much luck on the web, I'm trying to get as low power light as I :can, they don't have to be very big... anything the size of a standard :LED or maybe up to as big as a penny would be fine... bigger than that :would be too big... it's just a panel indicator : :thanks
You probably want a ready-made panel mount lamp for your application. Playing around with NE-2 lamps and resistors and putting them in a suitable housing is painful.
Digikey, and no doubt others, have such lamps to suit both your requirements
"High intensity" neon lamps such as the NE-2H (C2A) and the "mini-NE-2H" (A1C) only use 2-2.7 mA average current. I hope that you are as aware as I am of LEDs that get similarly bright at less current than this.
Most InGaN green LEDs (nominal wavelength 520 to 535 nm) in my experience do plenty good and well with average current of .5 mA or less.
Cheaper ones such as TT Electronics / Opto Technology OVLLG8C7 will do well in AC circuits with a halfwave rectifier and series resistor, along with a second diode antiparallel to the LED to protect the LED from reverse polarity resulting from leakage through the halfwave rectifier. I would say that one glows plenty bright in this application with .36-.4 mA average current, which means that a 150K resistor should be good here at 120 VAC. Although, I would like to caution that an LED with halfwave-rectified 60 Hz AC sometimes has its flicker being visible.
For a "more premium" super-low-current 120VAC indicator with cost likely getting to reducing ROI unless most-alarmist forecasts of future energy costs pan out, use a Nichia NSPG520AS or similarly super-efficient efficient-at-low-current low power green LED (maybe likely by Nichia). For less flicker, connect this LED to the DC leads of a suitable bridge rectifier (voltage rating can be low). Put the dropping resistor in series with one of the AC leads of this bridge rectifier - of value to pass maybe .1 mA, .15-.2 mA if you need brightness "on a high side". This means at 120 VAC, resistor value is 1 meg, 680 or 470 K if you need brightness on a higher side.
As for 28 volts - my experience suggests to me that this is often DC. If your 28 volt application is AC, use the above with resistor values roughly 22% of above. (33K for TT Electronics / Opto Technology OVLLG8C7 antiparalleled by a diode when used with a halfwave rectifier, 220K or maybe 150 or 100K with Nichia NSPG520AS with fullwave bridge rectifier).
If the 28 volt application is DC, I would advise .5-.55 mA with a cheaper InGaN green LED (47K resistor) or .11 mA, .25 mA high side with the best that Nichia offers in this area (resistor value 100K to 220K).
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.