Twin Tube HF fluorescent lighting for the workshop

[Adam HarrisParticipant @adamharris13683]

Despite the original intent of going LED for workshop lighting (garage 2.5m wide x 7m long) I ended up this week buying five 6' Twin HF 70w Flourescent lamps (Viper from LCD Direct) which do not have the dangerous stroboscopic effect on moving machinery. Only so far wired up 2 in series to one on/off switch , and after 5 seconds of light the mains board RCD trips out (it is a 63A 230V RCCD that trips at 30mA). I have now learnt the expensive way that fluorescent and RCD's are not easily friends! Is there something to be done to cure this problem or should I try to return them? Would it make a difference to have a separate on/off switch for each light and start them each in sequence separately? Is the overall running leakage on total ten 70w tubes simply incompatible with a 30mA current trip RCD? Any suggestions from those using these twin HF lights? Thanks for any help

[Adam HarrisParticipant @adamharris13683]

[Andrew TinsleyParticipant @andrewtinsley63637]

I have always used ordinary fluorescent tubes plus chokes and I have never had any stroboscopic effects! Even if you did, the racket that any machine tool makes would tell anyone that the system was working and not stationary!

HF driven tubes are a bit of a pigs ear. They should be a touch more efficient, but they radiate all sorts of high frequency hash. This can cause the effect you are experiencing. I would never use HF gear in a workshop, mucks up my radio!

Andrew.

[Adam HarrisParticipant @adamharris13683]

Yes well I found some very convincing advocates online for twin HF tube in the workshop along the lines of more efficient and no stroboscopics (the twin cancels each other's frequency out), but they did not come from this illustrious forum (perhaps Practical Machinist?). Anyway no warnings mentioned of the Pig's Ear and RCD's!

Edited By Adam Harris on 11/10/2018 21:58:49

Edited By Adam Harris on 11/10/2018 22:01:29

[John HaineParticipant @johnhaine32865]

Have replaced 3 fluorescents with LED "tubes" and use LED work lights almost exclusively in the workshop. No problem with strobe effects.

[Adam HarrisParticipant @adamharris13683]

John, did you replace with LED because of RCD tripping problems?

[egaParticipant @ega]

Plus 1 for the LED tubes – a revelation.

[Alan Waddington 2Participant @alanwaddington2]

Iv’e recently ditched the fluorescents and fitted eight of these bad boys……..no flicker or strobe effect, instant switch on, and flipping bright

**LINK**

Edited By Alan Waddington 2 on 11/10/2018 23:40:56

[SandgrounderParticipant @sandgrounder]

I use LED floodlights and LED GLS bulbs in my small workshop and I do get a slight strobe effect, but like Andrew says in post 2 the noise of the machine is more than enough to warn you that it's working.

[Gary WoodingParticipant @garywooding25363]

I replaced the 3 twin 6ft fluorescent tubes (not HF) in my workshop with LEDs. My old eyes cannot detect any flickering or strobe effects. The LEDs are far better with a cleaner, purer, light. And instant on/off.

[David TParticipant @davidt96864]

I have two single fluorescents in the workshop; never had a problem with nuisance RCD trips, and never noticed a stroboscopic issue either. Surely any stroboscopic effect would be limited to harmonics of 50Hz though? So any stroboscopic effect may lie dormant for years until one one day something just happens to spin at the required RPM?

[KWILParticipant @kwil]

As an experiment I have in the past, wound up the spindle speed as set by the VFD from 0 to max and have not found this alleged strobe effect.

[Andrew TinsleyParticipant @andrewtinsley63637]

I don't want to stir controversy. However the resounding vote for LED tubes may be a mite misleading. People usually swop from fluorescent to LED tubes because they are dissatisfied with the lighting levels. They are then amazed how bright the LED tubes are. However they are usually comparing old worn out fluorescent tubes with new LED tubes. Need I say more?

With regard to the colour temperature of tubes. There is a much wider choice of colour temperature in fluorescent tubes than for LED tubes. People never ask for a colour temperature when they buy tubes and therefore usually get around 3000K tubes, as they are the most common.

LED tubes are not necessarily free of flicker, it depends on the circuitry of the drivers. Having said all that, LED tubes are more efficient. At the current time they are also quite a bit more expensive, which tends to reduce their efficiency advantage over life. One other thing to note is that the claimed lifetime of LEDs is usually very optimistic. The life is critically dependent on temperature. The higher the running temperature, the shorter the life! It only takes a small temperature rise to significantly reduce the lifetime to failure.

Obviously LEDs are the future, but right now, the advantages are not as large as people think. When the chokes fail on my fluorescent tube installation, I will probably change to LED tubes, until then, I shall keep my 6000K fluorescent tubes. By that time, the LED tubes will be significantly cheaper than they are now.

Andrew.

[SillyOldDufferModerator @sillyoldduffer]

Those who've failed to find stroboscopic effects haven't looked hard enough!

That said, the effect is often small and I doubt it's much problem in practice in a small workshop where the noise of a machine running is often enough warning in itself.

But imagine you're in a large machine room lit entirely by fluorescent lights all flickering together at 50Hz with several noisy machines racketing away in the background. Perhaps you're wearing ear-defenders. Also, you're unluckily turning a strongly contrasted lump of bright steel and it happens to be rotating with just the right diameter and rpm to sync with the lights. A moment's inattention and you could get caught. Bit unlikely, not impossible. Actually, stroboscopic effects are much more obvious with largish objects like poorly lit fan-blades and gear wheels. Beware of them!

I have a mix of HF and conventional fluorescent lighting with HF over my lathe. It creates an effect not unlike strobing because the light bounces off the rotating jaw into my eyes at the same angle:

Not a camera trick, the photo is very like what I see – a chuck that at a careless glance looks as if it's stopped. As with a lot of accidents, several factors are often required to come together. I might fall for it if I was tired, drunk, distracted and unlucky. But not normally!

The other end of my workshop has ordinary fluorescent lights. Here I notice true strobing once in a while, but it's not strong enough to fool me. It's hard to imagine it causing an accident. The best way to see strobing is to spin an object with black stripes on a white or shiny background in low ambient light.  Used to be quite hard to see adjusting the speed of a teleprinter governor with a neon bulb and very obvious at the strobe lit Discotheque of my youth.

Another factor may be the age of the tube and the type of phosphor inside. Some tubes flicker a lot more than others, and old tubes seem worse than new ones.

HF tubes flicker much faster than the human eye can detect and the effect isn't synchronised between lamps. Like LEDS, they don't strobe.

Dave

Edited By SillyOldDuffer on 12/10/2018 11:45:23

[KWILParticipant @kwil]

Interesting 2 jaw chuck does not fool me into thinking it is not rotating.

[Brian Sweeting 2Participant @briansweeting2]

Just for info but we used to check our contactless tachometers by pointing them at a fluorescent tube to check that they were reading correctly. 3000rpm IIRC.

[Andrew TinsleyParticipant @andrewtinsley63637]

In an amateurs workshop, strobing is unlikely to fool anyone into thinking that the machine isn't in action. Large workshops with multiple people are another thing altogether.

Yes I calibrate my tachometer with a fluorescent tube. You can still get the effect with a tungsten filament lamp (although much less of a variation). The eye can't respond to 50 or 100 Hz unless you are a very odd man out, so this isn't the flicker you see with an old fluorescent tube.

I reiterate that LEDs are not always flicker free. It depends on the electronic drivers. Some of the cheaper drive circuits produce the same sort of 50Hz flicker as a fluorescent. You get what you pay for in driver circuits.

Andrew

[HughEParticipant @hughe]

Adam,

Back to your OP question and the tripping of the RCD. This could only happen if there was a imbalance of> 30mA between the L and N. I do not know what the driver circuits in these are like but I suspect there is a some form of filter circuit that could be the cause. Did you really mean you have connected them in series?

Hugh

[Neil WyattModerator @neilwyatt]

My dad had several cardboard 'records' with circular patterns of lines in the workshop at his shop. They were for adjusting the speed of record players together with a suitable light.

I recall some decks had a built in pattern round the edge of the platter and a small neon.

Neil

[Mike PooleParticipant @mikepoole82104]

My Pioneer deck still has the strobe track cast in the platen and is illuminated by a neon source, it is getting on a bit now as it was new in about 1978

Mike

[Adam HarrisParticipant @adamharris13683]

Hi Hugh, thank you for directly addressing the RCD issue. Yes I wired the two in series and RCD tripped after a few seconds. I have now wired these two independently with different switches (although both switches coming off the same supply cable) and everything is fine. What does this mean in terms of interference between units. Should one never wire fluorescents in series? Or is it the starting of both at the same switch that causes excessive surge? In other words is series wiring ok as long as there is a startup delay between each (ie an on/off switch between each)?

[Adam HarrisParticipant @adamharris13683]

Hugh actually sorry I had been wiring in parallel rather than series – I had been wiring L to L to L , N to N to N etc. (Series would be Plug L to Light#1 L, then Light#1 N to Light#2 L , then Light #2 N to Plug N). Anyway, since I have been wiring in parallel, the RCD must have tripped because of excessive startup surge with all startups simultaneous, OR some mysterious frequency interference between units??

[SillyOldDufferModerator @sillyoldduffer]

Posted by Andrew Tinsley on 12/10/2018 14:47:01:

…Yes I calibrate my tachometer with a fluorescent tube. … The eye can't respond to 50 or 100 Hz unless you are a very odd man out, so this isn't the flicker you see with an old fluorescent tube.

…

Andrew

The Wikipedia article on 'Flicker Fusion Threshold' is worth a look. New to me is the statement under 'Lighting':

"Fluorescent lamps using conventional magnetic ballasts flicker at twice the supply frequency. Electronic ballasts do not produce light flicker since the phosphor persistence is longer than a half cycle of the higher operation frequency of 20 kHz. The 100–120 Hz flicker produced by magnetic ballasts is associated with headaches and eyestrain.^[12] Individuals with high critical flicker fusion threshold are particularly affected by light from fluorescent fixtures that have magnetic ballasts…"

This may explain why different people have different experiences. Flicker is much more likely if you have a high fusion threshold AND ballast fluorescent tubes.

Also, it seems that electronic ballasts don't work at 100Hz, and that the HF lamps are even higher frequency.

I feel the need to wire a phototransistor up to my oscilloscope to see what's coming off the various lamps I own. Watch this space…

Dave

[Alan VosParticipant @alanvos39612]

Posted by Adam Harris on 11/10/2018 21:22:06:

Is there something to be done to cure this problem or should I try to return them?

If your problem is still unresolved come Monday, I will ask at work. They know most things about tubes, control gear, and the behaviour of circuit breakers.

[HughEParticipant @hughe]

Hi Adam,

Glad to see you have sorted it. I would think that during startup they have a small amount of leakage when added causes your RCD to trip. You triggered my curiosity i will do some research on these lights as I am about add lighting to my garage. In the workshop I have used LEDs as they came free no flicker that I have noticed.

Hugh

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