Cheap 12V fluorescent lights

[BT Humble]

As the next step towards decreasing the cost of lighting installations in my remote-village-solar project, I decided to have a look at the light fittings.

Currently, we're using 8W 12V "trouble lights", which cost AUD$10 each and come fitted in a plastic tube.  These are quite robust, and only draw 350mA, but give a very "blueish" light.  A similar 16W version costs AUD$20.  They look like this:

Since the idea is to come up with a design that the villagers can build for themselves, I did some researching of various circuits and decided that this one was probably the best fit for my use:

http://www.talkingelectronics.com/Projects/
FluorescentInverter/FluorescentInverter.html

Its positive points are:

• Cheap;
  
• Simple;
  
• Not necessary to disassemble and rewind E-I transformer cores;
  
• Robust;
  
• Reasonably efficient.
  
  

On the down side:

• Makes AM radios whistle like teakettles;
  
• Probably not as efficient as an E-I core transformer.
  
  

The changes that I made to it were:

• Use a 50mm (2") section of ferrite for the transformer (it comes in 100mm lengths, this way I get 2 for the price of 1);
  
• Wind the secondary (5 layers, 90 turns per layer) first;
  
• Wind the primary (1 layer, 52 turns) next;
  
• Wind the feedback (12 turns) last, in the opposite direction to the primary;
  
  

I've designed a PCB to allow for a simple and robust assembly, and a batten fitting made from 40 x 20mm pine.  I think that the RF interference will be minimised by housing the circuit board in an aluminium box, but I didn't have time to try that yesterday.  The box could then double as a heatsink for the transistor.

Here's the completed light:

A close up of the circuit board.  The strip of aluminium is a heatsink for the transistor, and the transformer is insulated with masking tape:

Powered up, and consuming 560mA:

The total cost (including tube) should come in at a very competitive AUD$7.  

I'll post the PCB artwork and my changes to the circuit, if anyone is interested.

BTH

[Trivo]

Went to the site, boy do they have some interesting stuff and in plane english easy to loose a few hours there. Where do you buy the ferrite?

trivo

[BT Humble]

In Australia, either Jaycar or Dick Smith sell them.  If you're in the USA, maybe Radio Shack?

BTH

[wooferhound]

Ferrite cores are used in almost all AM radios as the antenna.

[ghurd]

The trouble lights are just that. Trouble.

A 12.6v light at 0.350 is 4.41 Watts including losses. Watts up with that?

Is it 8w or 4w?

The life expectancy is very low. Amazingly low in my experience (a month is good).

The decent 11w 12vdc CFLs I have used are MUCH brighter. So much I can't explain it. 7 to 10 times brighter is a guess.  I bet the decent 7w CFLs are about as good as the 11w, but the current draw is soooo close to the 11w, I just use 11w now.

The whole idea is to get a lot of light, for a little power, for a long time,and not much money.

Don't use the trouble lights. They are not bright, efficient, or long lived. IMHO.

G-

[Galagedara]

Hay B.T.Humble,

Many thanks for the fantastic articale about floro lighting! I really appriciate the simple way of giving the know how to guys. In fact I was looking some thing lik this. I have bought some Floros a set of three with a transformer stepping down to 12 volts AC. I bought this in view of operating from 12 Volts DC which gave me a problem as it is for AC. Unfortunately those bulbs are a curved type. ( you mentioned that they are not very effective) I will definitly try your construction to power this.

I am unable to check all the data for this lamps as all my things are packed fora long jurny from Denmark to Srilanka. I have book mark your page to my favorits which I will refer it later.

My idia is to make some lighting system as in Srilanka power failiers are just like alternating current!!! I mean just so high in on off! I am planning to have solar and wind, I hope my dream come true.

I thank you so much again for the fine articale, keep on the good work!

Kind Regards!

Leonard

[Flux]

Be interesting to see how the tubes last cold striking them. Expect one end to go black quite quickly. Reverse them occasionally to equalise the wear on both ends.

Will probably strike tubes that no longer work in normal fittings when the heaters are tired.

Try an earthed wire strip taped along the tube to make striking easier.

Flux

[BT Humble]

Be interesting to see how the tubes last cold striking them. Expect one end to go black quite quickly. Reverse them occasionally to equalise the wear on both ends.

Will probably strike tubes that no longer work in normal fittings when the heaters are tired.

Try an earthed wire strip taped along the tube to make striking easier.

Yes, it's all part of the experiment.  Since it's not using the heater filaments it should work with otherwise-dead tubes, as you say.  From time to time I've seen boxes of 4' tubes (as in, a box of 2 or 3 dozen) dumped at recycling centres, which would be a good source of them.

The pair of 40W and one 20W tubes in my shed have been running from similar inverters for almost a year now without any blackening, so maybe it's a winner?  I think that the climate here (and in Fiji, where they're going to) would be better for fluoros than the 20-below-freezing that most of you guys seem to get, too. ;-)

BTH

[BT Humble]

The trouble lights are just that. Trouble.

A 12.6v light at 0.350 is 4.41 Watts including losses. Watts up with that?

Is it 8w or 4w?



Essentially (from what I've seen) you get a brighter output by running a fluoro at 2kHz than you do at 50Hz (or 60Hz, in your case).  So you don't need to put as much power through it to get an equivalent light.  By slightly under-rating the tube you also get a longer life out of it.

The life expectancy is very low. Amazingly low in my experience (a month is good).

The decent 11w 12vdc CFLs I have used are MUCH brighter. So much I can't explain it. 7 to 10 times brighter is a guess.  I bet the decent 7w CFLs are about as good as the 11w, but the current draw is soooo close to the 11w, I just use 11w now.



The first couple of them that I bought were very poor quality, and were actually drawing about 600-700mA for an 8W tube.  They also had no heatsink on the transistor, and so burned it out within a couple of days.  A little later I found a source of a much better quality version (for only $2 more) that had heatsinking on the transistor and ran barely-warm as opposed to finger-burning-hot.  So I bought 30 of them.  They're a little less bright, but appear to be lasting well so far.

CFLs are driven quite hard, hence the bright light from a small package.  Some of them (especially the cheaper ones) get quite hot, especially in the base where the inverter circuitry lives.  Heat=wasted energy.  They're also a more focused point-source of light than you get from a long tube (I'm echoing a bit of what the guy on the original site had to say).  I agree that CFLs are very useful and have their place, but for this particular application I think that the longer tubes are the way to go.

The whole idea is to get a lot of light, for a little power, for a long time,and not much money.



I concur! ;-)

Don't use the trouble lights. They are not bright, efficient, or long lived. IMHO.



We'll use up the batch that we've already bought and sent over there, but I won't be buying any more.

BTH

[BT Humble]

Hi Leonard, I just thought I should point out that the website I referred to isn't mine - I was just building on his work a little bit.  I'll try to get a circuit diagram and PCB layout done and posted here soon - watch this space!

Best of luck in Sri Lanka, too.

BTH

[Galagedara]

Hay BTH,

Its OK, even its not your site, I am greatfull to you publishing itfor the benifit os others!

Many Thanks and looking forweard to see the PCB art work and the diagram.

Kind Regards!

Leonard.

[RobC]

Great project but I am a little confused by the resistors. Example (180R) 180 ohms ?

RobC

[BT Humble]

Great project but I am a little confused by the resistors. Example (180R) 180 ohms ?

It's a shorthand notation, that seems to be the fashion these days.  You use either "R", "K" or "M" to replace the decimal point, eg:

1. R8 = 1.8 ohms
   
180. R = 180 ohms
     
1. K8 = 1,800 ohms
   
180. K = 180,000 ohms
     
1. M8 = 1,800,000 ohms
   
180. M = 180,000,000 ohms
     
     

BTH

[BT Humble]

Let's try that again, the formatting got a little skewed there!

Great project but I am a little confused by the resistors. Example (180R) 180 ohms ?

It's a shorthand notation, that seems to be the fashion these days.  You use either "R", "K" or "M" to replace the decimal point, eg:

1R8 = 1.8 ohms


180R = 180 ohms


1K8 = 1,800 ohms


180K = 180,000 ohms


1M8 = 1,800,000 ohms


180M = 180,000,000 ohms





BTH
 

[RobC]

Thanks for the help K & M I understand but that R was really confusing me. RobC

[ghurd]

I can't get the link to work. Several tries on several days. Changed it around some and still can't get it.

G-

[finnsawyer]

Seems like an unnecessary complication.  I think they should deep six it.  Just my opinion.

[commanda]

Decimal points often disappear in photocopies, faxes, etc. That's why the multiplier is used in its place. Not a new idea, been around for at least 20 years that I can remember.

Amanda

[deerslayer660]

   help i cant get link to work eather any suggestions?

[RobC]

I just kept trying and finally it worked.RobC

[deerslayer660]

   ive been tring for 4 days now and the site dont work anybody post a shcmatic

for inverter ckt for me would like to try this  I have also bought this same trouble light got mine from odd lots in ohio the inverter ckt in the light sucks  i have one in my camper it works great so i got another for my house power backup system during the big ice storm this lite worked for 20 min and poof prety blue smoke took it apart and transistor had shorted took it back to store and got another  12min poof

same problem since im so stubbern took this lite back to a differnt store and got another  it works fine now for about 10 hrs   i guess i schould have just put in another trans in the light been cheaper than buying gas oh well   any way i still think the lights are a good deal at 4.99$  the light looks good the problems i have found are all in the inverter ckt and thats fixable  you will pay 4.99$ or close for just a tube  the lights heat sink for transistor runs ground all the way the lenght of tube so helps it light all in all worth the money

[Norm]

I just can't get that link that you posted?

 got another way to get to it?

           ( :>( Norm.

[ghurd]

6 days. No luck.  G-

[BT Humble]

Sorry for the delay guys, but I've been away from home since Wednesday and haven't had a chance to look at the board.  I'm getting some photos, circuit diagram and PCB artwork together for both this and the LED voltmeter at the moment, but time is a bit of a problem.

For the time being, here's another site offering much the same circuit with a description of how it goes together:

http://www.aaroncake.net/circuits/40wflamp.htm

There's an error on that diagram, in that C2 should be a 0.1uF polyester or ceramic capacitor.  An electro will work fine too, if you can get one the right size.

If you're using a smaller tube you can retain the same numbers of turns on the transformer, just increase the value of C2 to 0.5uF or so.  This can also be done to run a tube at a reduced power consumption and brightness.

Also, I recommend doing the windings as secondary (450 turns), then primary, then feedback.  Also, I insulate each layer with strips of masking tape running the length of the ferrite rod (ie. not spiralled).  That way it will all neatly fit on a 50mm length of ferrite, and the leads for the primary and secondary are easy to identify:

(It also makes it much easier to mount directly onto a PCB, since the four 0.63mm primary and feedback winding ends are plenty stiff enough to support its weight).

I'll have a full article in a few days, I promise.

BTH

[BT Humble]

Amanda!  Good to see you back again, we (well, Richard and myself) were just wondering the other day what had become of you. ;-)

BTH

[deerslayer660]

  in article it said to ues different size wire for primary and feedback is thie nessary? or can it all be same size wire?  also do you wind in differnt directions

for all or just the feedback thanks george

[BT Humble]

in article it said to ues different size wire for primary and feedback is thie nessary? or can it all be same size wire?  also do you wind in differnt directions

for all or just the feedback thanks george

I used 0.63mm for the primary and feedback coils, and 0.4mm for the secondary.  

The primary and feedback need to be wound in opposite directions because they interact, the secondary just needs to have all its turns in the same direction (ie. don't accidentally reverse your winding direction when you start a new layer!)

BTH