Light bulb not fully lighting with correct wattage?

Question

Ok, this is kinda complicated so here it goes. I have a 254nm Ushio ultraviolet light bulb that is 10.5 Volts and 3 Watts. I connected 3 batteries in parallel which each are 10.5 Volts, 100mAh.

When I connected them I was expecting a blue light which I've seen pictures of on the Internet of this bulb working, however the result was a faint red glowing on the bulb's filaments with no blue glow. I tried adding a 4th battery and it gave the same results.

Am I missing something as to why the bulb shouldn't light up at full power?

Answer 1

This is not supposed to happen if it is a good sample of product. Anyways, maybe I can try to give you the reason as to why this might happen. The overall voltage gain of the circuit might not be enough which is required to give you the blue glow (as we know, blue beams contain the most amount of energy in the visible light spectrum). You can check out the batteries if they are still active with their full 10.5Volts ratings. You can also check out the contact points of the batteries. Their might be some lose contact points. Fix them and hopefully you will have the blue glow.

Answer 2

I suspect you are using a battery similar to the EVEREADY NO. EN177A, if so, that is a small battery designed for very low current, it's rated capacity is at less that 1mA load, and the highest current shown on the data sheet is about 12mA.

If you are using 3 batteries in parallel for a 300mA load, you need 100mA per battery, which is probably much more than the batteries can put out without a _significant_ voltage drop. If you have a voltmeter, you might check the voltage across the lamp, I wouldn't be too surprised if it was less than 5V.

You might try, maybe 7 AA cells in series. that would probably be more practical than 30 or so 177's in parallel.

[EDIT]  when I did a search for "10.5V 100mAh" the EXELL cell was the first thing I found, but I couldn't find ant technical information for it so that is why I suggested it was similar to the Eveready, which I did find a data sheet for.

I'm surprised he 7 AA cells didn't work, I don't think 300mA is unreasonable for an AA, at least not for an alkaline or NMIH (though due to the lower voltage on NIMH you might need 8 of them)

I suggested AA because I assumed size was an issue since you were using the 177,  D cells might be better for that load, but again I am surprised the AA's didn't work.

To get a useful voltage reading you do need to measure across the lamp (that is, in parallel with the lamp, not in series with it, series connection is for current) , while it is connected to the batteries, measuring the unloaded batteries is not so useful in this case.

I don't really understand your current reading, if you got 0.5 on a 20mA scale, I wouldn't expect any visible glow, and for it to be that low your batteries are effectively dead

Answer 3

That battery is 100 ma-hr, which is NOT 100mA. It's good probably for only a few ma, so you would need a lot of batteries to get 300 ma.

If you put your meter across the bulb you would probably only see a few volts. If you do see 10 volts, then the bulb is defective.

You said you checked the voltage, but you didn't say what voltage you checked, with the lamp connected or not.

Get a DC supply, or 7 D cells.

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