Driving EL wire with Supertex HV850 family drivers

Question

I was considering driving EL wire with Supertex'es ICs or some equivalent ICs from another manufacturer. The ICs are designed to drive EL panels not EL wire. Would this still work?

Supertex'es ICs are rated for "lamp sizes" up to 42 square inch. My wire is 2.3 mm in diameter and 20 meters long. I'm going to assume 2.3 mm is the diameter including the outer protective sleeve and the actual diameter is probably somewhere around 2 mm. Looking up the formula for a cylinder's surface area I determined that my EL wire has surface area of about 2513 cm² (about 390 square inch). That's way too much for those ICs.

According to this calculation I could drive up to 2 meters of EL wire with these ICs. But is this calculation applicable to EL wire at all?

Answer 1

The area is not really what loads the driver- what matters is the total capacitance (and the voltage, and frequency). The wires have a spiral wire on the outside which doesn't have as much capacitance per unit area as a flat panel.

The HV816 claims to be able to drive 150nF, which they say is about 42in^2 of EL backlight.

From this link, they claim the capacitance of their EL wire is about 1nF/foot, so 20m should be about 66nF, in which case the Supertex HV816 should be able to handle the capacitive load, and if the voltage and frequency are right, it should be okay. Check the specs on the EL wire you are using (or measure it).

Answer 2

also it is worth mentioning that EL Wire also has a maximum VPP which isn't much more than 300V, I have had some fail at 339V. The thinner the dielectric ie angel hair the larger the chance of a failure.

General rule, if it looks "patchy" then the frequency is much too low. I have run it up to 7 kHz and although it was crazy bright the wire didn't last long (less than an hour before a catastrophic failure)

Some folks run this directly from the mains, NEVER DO THIS!!!!! always use an inverter even a simple one, a good circuit current limits input voltage and then increases frequency to around 500Hz. some even have a trimpot so you can set this parameter as it affects wire color and brightness on the green/blue wire.

Have also used the HV850, it needs input voltage regulation to work properly ie 4.2V and if you try and run it directly from a lithium cell typically there is still useful power left well before the chip shuts down through under-voltage. It does work well for backlights though with my own modification of a frequency feedback using CdS photoresistor so the backlight is brighter during the day when needed.

Answer 3

The main consideration in driving an Electroluminescent display or wire is the EL Capacitance, Frequency, and Voltage.

The area of a EL display/lamp/wire is just a byproduct the Capacitance per square inch, which you can find on the EL Wire's datasheet.

The Supertex HV816 is a high voltage Electroluminescent (EL) lamp driver designed for driving a lamp capacitance of up to 150nF, or an area of approximately 42 square inches.

The other two factors are the voltage, and the frequency. The HV816 has a frequency output of 100Hz to 1kHz. EL wire is typically stated to require a higher frequency than EL panels (1~2kHz vs 300~500kHz). The HV816 also has a voltage output of 360VPP, which again, EL wire is typically stated to require a higher voltage than EL panels (300VPP vs 150VPP). As to why that's required, I have yet to get a solid answer on my question on that topic.

Answer 4

also worth adding a series resistor. From experimentation 33K seems to work and limits drive current to a sensible level.