How do HID torches work?

[Andrew H]

Apologies if this has been covered before, the search tool won't accept HID and I'm not about to trawl through 65 pages of posts.

Can anyone explain how HID torches work in technical terms. I understand that it is a discharge lamp and has an inductive ballast, am I right in assumming that the lamp is a capacitive load and the ballast is for power factor correction, hence the torch generates an AC power supply?

Hope someone can follow that!

Andrew

[Gizmo]

I'm quite interested in this as today was chatting with my LDS and he recommened the UK Light Cannon(I think this is what it is called), says it is quite popular at his local club and also highly recommended. This uses HID, so would be interested to hear the forums view on this.

[wreckweasel]

Originally Posted by Andrew H

Apologies if this has been covered before, the search tool won't accept HID and I'm not about to trawl through 65 pages of posts.

Can anyone explain how HID torches work in technical terms. I understand that it is a discharge lamp and has an inductive ballast, am I right in assumming that the lamp is a capacitive load and the ballast is for power factor correction, hence the torch generates an AC power supply?

Hope someone can follow that!

Andrew

Nearly right

The ballast is a DC Voltage pump circuit (output circa 10kV). In the start up phase it produces micro second pulses to initiate the arc, which are at a high inrush current (+10 amps), but once struck the operating current plummets.

So basically, you've got a voltage pump and a current regulator circuit.

For the others, the Arc is basically between two electrodes in the bulb head, once struck it melts the metal in the head and its this that generates the distinctive light colour.



/Zak

[hazey]

The bulb in the light cannon (and others) is a Welsh Allyn solarc bulb. If you want to read about it have a look at the following link.

http://www.walamp.com/lpd/faq/index....&action=narrow

Regards
H.

[Fathoms Down]

Originally Posted by Gizmo

This uses HID, so would be interested to hear the forums view on this.

I have one and its very good. The only thing I have against it is that its not umbilical but, considering its price, I can live without that for the moment.

[Spider]

Originally Posted by Nick Bown

I have one and its very good. The only thing I have against it is that its not umbilical but, considering its price, I can live without that for the moment.

I also have an HID light cannon (a Birthday pressie from the other half) and the light is better than my previous torch - a UK D4. The rechargeable version seems a lot more expensive than the one that takes batteries - I found it cheaper to buy eight batteries and two chargers from Argos.

The main disadvantage compared to other torches on the market is that you need to unscrew the torch to charge it and then make sure it's done up properly - no grit on the O-ring, not too tight or too loose etc, otherwise you get a flood.

The other consideration is the price of the bulbs - not cheap to replace!

And like Nick said an umbilical would be a definite advantage. I'm saving up the pennies for one as well.

[Padowan]

I have a Custom Divers HID umbilical and it's awesome; compact lasts for about 4 hours on a charge, lovely white light, only put to shame by 2 other torches I've seen: a Greenforce Impact 100HID (30W HID) that my buddy uses, and a 60W HID (yes 60W!!) FaMi that our trimix instructor lit up the whole quarry with on our course, for a laugh! Now that really was awesome...

I even dropped in the first day out, and cracked the lamp, but the bulbs still intact, and has kept working for well over a year like it...

[Spider]

I found this paragraph in US patent 6,679,619 titled "High intensity discharge (HID) lamp with integral ballast and underwater lighting systems incorporating same":

"The lamp contains an anode and a cathode and a mixture of mercury, argon and other chemicals. The anode and the cathode are coupled to a ballast having a DC power input. When a DC voltage (9-16 VDC) is applied to the power input of the ballast, the ballast begins a start-up sequence. The ballast first produces a series of high voltage (25 KV) high frequency (33 KHZ) pulses that ionize the gases inside the lamp. During this sequence the ballast monitors the resistance of the lamp. When the gases have been sufficiently excited, an arc is struck across the anode and cathode. After the arc is struck, the ballast applies a reduced DC voltage to the anode and cathode of approximately 60 VDC. The ballast continuously monitors the resistance of the lamp and controls the current to the lamp in order to maintain the arc and prevent overdriving. The color of the light produced by the HID lamp is determined by the mix of material (compounds and/or gases) contained in the lamp and the extent to which they are excited by the continuing current. Typically, the color temperature is in the range of 4700-6500.degree. K."

I hope it makes more sense to you than it does to me!