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Cold Cathode CFL.

C

Clive Mitchell

Jan 1, 1970
0
Remember we said that he first person to get a cold cathode compact
fluorescent lamp would sacrifice it for the betterment of the group?

Here it is...

http://www.emanator.demon.co.uk/cclamp.jpg

Not much to write home about.... The VERY simplified schematic doodled
in the picture shows that it's basically a standard CFL circuit, but
using a step up transformer instead of the choke. This lamp in
particular is notable for the complete lack of suppression components
and no electrolytic capacitor.

The lamp is quite noisy in operation and as you would expect with the
lack of smoothing you get a 100Hz (50Hz) buzz with a relatively high
pitched squeak superimposed.

I guess the lack of an electrolytic to dry out is good, but the
conventional transformer for driving such a long thin tube is a bit
dubious from a winding insulation perspective.
 
V

Victor Roberts

Jan 1, 1970
0
Remember we said that he first person to get a cold cathode compact
fluorescent lamp would sacrifice it for the betterment of the group?

Here it is...

http://www.emanator.demon.co.uk/cclamp.jpg

Not much to write home about.... The VERY simplified schematic doodled
in the picture shows that it's basically a standard CFL circuit, but
using a step up transformer instead of the choke. This lamp in
particular is notable for the complete lack of suppression components
and no electrolytic capacitor.

The lamp is quite noisy in operation and as you would expect with the
lack of smoothing you get a 100Hz (50Hz) buzz with a relatively high
pitched squeak superimposed.

I guess the lack of an electrolytic to dry out is good, but the
conventional transformer for driving such a long thin tube is a bit
dubious from a winding insulation perspective.

The efficacy is lower without the electrolytic capacitor
since the HF is then highly modulated at 100 Hz.

--
Vic Roberts
http://www.RobertsResearchInc.com
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A

Andrew Gabriel

Jan 1, 1970
0
The efficacy is lower without the electrolytic capacitor
since the HF is then highly modulated at 100 Hz.

However, it probably has a power factor of 1, and it should
be dimmable with a regular cheap dimmer (providing you have
enough of them to reach the dimmer's minimum power rating).

Clive, what is the make and power rating, and where did
you get it? Looks like it's a GU10 form factor.
 
C

Clive Mitchell

Jan 1, 1970
0
Andrew Gabriel said:
However, it probably has a power factor of 1, and it should be dimmable
with a regular cheap dimmer (providing you have enough of them to reach
the dimmer's minimum power rating).
Good point. In hindsight the circuitry is closer to an electronic
halogen transformer but with a somewhat different winding ratio.
Clive, what is the make and power rating, and where did you get it?
Looks like it's a GU10 form factor.

It's a Lloytron Lighting lamp for GU10 base and with a rating of 4W
(equivalent to a 20W tungsten lamp apparently).

Gets pretty hot on the front when in use.

To quote:-

10,000 hours average life.
70 Lumens average light output.
Suitable for use outdoors. (?)
Not suitable for use with dimming circuits.
 
C

Clive Mitchell

Jan 1, 1970
0
In message said:
Interesting that they say 'Not suitable for use with dimming circuits'.
The Bulbman site claims that dimming is one of the advantages of them.

Maybe it's just a blanket disclaimer left over from the hot cathode
versions.
 
V

Victor Roberts

Jan 1, 1970
0
Cold cathode CFLs with standard American medium screw base are
available here:

http://www.bulbman.com/index.php?main_page=index&cPath=4595_4596

Interesting that they say 'Not suitable for use with dimming circuits'.
The Bulbman site claims that dimming is one of the advantages of them.

Dimming is one of the advantages of cold cathode fluorescent
lamps. However, the ballasts used with these cold cathode
CFL may not be compatible with dimmers.

--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
 
V

Victor Roberts

Jan 1, 1970
0
Care to speculate why - if there is indeed no electrolytic resovoir cap?

Hard to tell. Perhaps they think the 150 nF capacitor will
draw large enough current spikes to damage the dimmer. Or,
similar to what Clive has said, they are so used to warning
against using their lamps on dimmers that they never
considered that this one might be OK.

BTW - the diagram shown in Clive's original post must be
incomplete. The "transformer" has only two connections to
the rest of the circuit - which would make it an inductor.
To do any "transforming" it needs at least three leads.


--
Vic Roberts
http://www.RobertsResearchInc.com
To reply via e-mail:
replace xxx with vdr in the Reply to: address
or use e-mail address listed at the Web site.

This information is provided for educational purposes only.
It may not be used in any publication or posted on any Web
site without written permission.
 
C

Clive Mitchell

Jan 1, 1970
0
Victor Roberts said:
BTW - the diagram shown in Clive's original post must be incomplete.
The "transformer" has only two connections to the rest of the circuit -
which would make it an inductor. To do any "transforming" it needs at
least three leads.

My quick sketch was highly abbreviated, but also very weird. On the
first scrutinisation it just didn't seem to have much connected to what
I would have classed as the common winding of the transformer.
 
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