Hi all,
i recently got some neon indicators, in-3 type, and am experimenting with powering them
They are rated for 90-110V @ 1.3mA
i thought the circuit i created would create a voltage divider to put it in that range when the pot is at max resistance
the tube is lighting but the pot is taking a drop of 130V, and the indicator is only getting 45V
Also, im measuring approximately 8mA of current to the indicator, and am unsure how to limit this though i am sure it is probably simple I=E/R stuff

Thanks for any help, im sure this is probably just my incompetence

 

heres the schematic, sorry it didnt upload the first time

 

They are rated for 90-110V @ 1.3mA

Neon indicator is of gas discharge type and does not follow Ohm's Law exactly. They take no current when off and requires some 70V or higher to fire. Then their terminal voltage drops to 40~50V.

They are extremely easy to use by just placing a current limiting resistor in series to limit the current.

When they lights, their terminal voltage can be as low as 40V as you have found out.

So the math to calculate the current limiting resistor is drive AC voltage - 40V and divides by the intended current.

(180 - 40) / 1.3mA = 107K

Any resistor with value from 100K to 120K will do nicely.

 

Thanks for the help
I was actually using dc, sorry i forgot to mention that but i doubt it makes much difference...
(i have no symbol for a dc-dc converter )

 

The above calculation would work with voltages of dc or AC rms.

 

Thanks for the help
I was actually using dc, sorry i forgot to mention that but i doubt it makes much difference...
(i have no symbol for a dc-dc converter )

The only difference as far as neon bulbs go is that only one element lights up with DC, whereas AC lights up both.

 

Because a neon has a negative resistance in it's curve, it can make a dandy flasher with a capacitor, resistor, and DC power source. Before LEDs they were quite popular.

http://members.misty.com/don/sillyne2.html

http://www.physics.brown.edu/physics/demopages/demo/em/demo/5f3060.htm

Part of the reason they were so popular is they would last for months, possibly years, off a single high voltage battery (back in the days of tube portable radios).

 

Thanks for the links Bill, those are interesting circuits.