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Fluorescent Tube "Strip light" Driver
LightSabres require High Voltage rather than batteries!
Why?
The plan here was to design a more efficient flurotube lighting driver. Unfortunatly, all I have done is build a standard light driver, as they are pretty efficient anyway! And you can't get more out than you put in, in this case. But it did have some intersting side effects...
The Circuit:
I tried 2 different ways of driving a HV coil to run a Fluro Light. The first was a common square wave driver (from my advanced flyback driver) and mosfet. This produced fairly usable light, but with an annoying flicker. I'm guessing this was caused by the half wave output only exciting the mercury vapour at each half cycle. It also produced non-moving "bars" of light in the tube. These I assume to be Standing Waves (This could be useful for "seeing" wavelengths).
A Simple HV AC transformer was constructed for the 2 tests:
The core is from a flyback transformer, the coil form is a solder reel, total winds are 1500 and the drive winds are 8 turns of copper 13A wire with a center tap (4 turns with 12V).
Basic Square Wave driver setup:
Input power was 12V at 1.5A, giving a total of 18Watts of power to light a 15W tube. This gives a 250mA loss and an efficiency of 80%.
The 2nd test: AC PWM driver setup:
For this setup, I used my previously constructed Plasma Sonic Driver board. This incorporates a TL494 SMPS controller ic.
Circuit Diagram:
This circuit provides the ability to drive 2 mosfets for a switched AC coil. The HV coil was run from 12V though, rather than 24V for this test.
The setup:
The sound input was left open for this test. The light output from this setup was flicker free and as bright as a normal flurolight. The intensity was adjusted by the PWM modulation. I also have run an 80W tube with this circuit (can be seen in the video at the bottom of the page and the "jedi" pic at the top).
Current consumption went up though. From 1.5A to around 3A at normal brightness. Both tubes would light all the way down to 50mA though.
Is there a use for the driver then?
Yes, if you want a sound reactive light and, are you ready for this... a radio transmitter! I expected this to happen from my previous uses of the circuit (see plasma sonic speaker).
Setup:
An audio source was applied to the PWM modulation (this controls the dead time of the output pwm). The modulated HV AC then controls the flurolight's intensity, or by setting the modulation potentiometer to low, causing the flurolight to turn on with the beat.
But hang on, you mentioned a radio transmitter?
Yes, by using an AC PWM through a HV coil, this is effectively and AM radio transmitter. Albeit not an amazing one, but it is able to be recieved upto 3 meters from the source at only 50mA input power!
So Yes you can have a radio transmitting, High Voltage powered Fluro Light. But not a more effecient one due to the fact that low pressure mercury discharges emit about 65% of their total light at the 254 nm wavelength (UV), which is neccessary to stimulate the bulb's fluorescent coating and emit visible light!
Video:
Or Download Below
A good article on Fluorescent lamps: WIKI The article is well written and very intersting about the history behind the common flurotube. I especially liked this bit:
"Fluorescent lamps can be illuminated by means other than a proper electrical connection. These other methods however result in very dim or very short-lived illumination, and so are seen mostly in science demonstrations.
-Static electricity (piezo gas lighters work too) -Van de graaf generators -Microwaving (Obvious) -Tesla coils (Been there, done that) -Capacitive coupling with power lines !! (Have seen this done, and it works very well) "
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Please do not reproduce anything contained within my website, as it maybe hazardous to your health unless you fully understand what you are doing. I cannot be held responsible. This website is copyright. © Oliver Hunt 2006-2008
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