Re: Neon Indicator Lights for Increasing Voltage?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Bert Hickman" <bert.hickman@xxxxxxxxxx>

Tesla list wrote:
> Original poster: "Tedd Payne" <teddp2@xxxxxxxxxxx>
> Hi All,
> I think somewhere I've seen or heard of a "ladder" of neon bulbs (the common
> little AC indicator type) which lights up in sequence with increasing
> voltage.  Can someone point me to such a circuit?
> Thanks
> Tedd

Hi Tedd,

Because neon lights have significant variation in turn-on voltage and their 
turn on voltages will be significantly higher than their extinguishing 
voltages, it will be very difficult to make neon indicator lamps work 
accurately in a voltage sensing/indicating circuit.

However, you could use a series of voltage comparators to create a bar 
indicator driver, but it's probably easier to simply use an inexpensive 
chip and and an LED bar display or discrete LED's. You can add an 
appropriate voltage divider ahead of the chip voltage input to scale the 
voltage for your needs. These display drivers come in either linear analog 
or log scaling (dB).

For example, see the following devices from National Semiconductor:
http://cache.national.com/ds/LM/LM3914.pdf  (linear scaling)
http://cache.national.com/ds/LM/LM3915.pdf  (dB scaling)
http://casemods.pointofnoreturn.org/voltmon/tutorial-full.html

In an 18 pin DIP package, the LM3914 is $2.70 in unit quantities from Digi-Key.

Best regards,

-- Bert--
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