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Slightly OT. Heat and a Bench Light ...

Discussion in 'Electronic Repair' started by Arfa Daily, Jul 4, 2008.

  1. Jim Adney

    Jim Adney Guest

    I believe everything you've told us about the bulbs. I have no reason
    not to, but 60 Watts is still just 60 Watts.

    There's no way to get more heat out of it than that. So either the old
    60 was actually less than 60 or the new 60 is more than 60 (or both.)
    Or you're mistaken about the new ones running hotter, which I agree is
    the less likely option.

    One other possibility occurred to me, and that is that your socket
    chose this moment to become resistive, which could have raised the
    total power above 60 Watts and concentrated that extra power
    dissipation in the socket - consistent with your observations. I'm not
    familiar with the socket you describe, so maybe you can judge the
    likelyhood of this. I suspect that if this had happened, the light
    output would have been affected and you would have noticed.

    -
     
  2. N_Cook

    N_Cook Guest


    I'd not appreciated that added effect with Ro80 "Apollo lander" shape bulbs.
    The filament is perhaps twice the distance from the socket as the same
    wattage but globular lamp. As well as reflecting forwards most of the
    rearward-going heat and light.
     
  3. Arfa Daily

    Arfa Daily Guest

    Presumably though, temperature will rise, both at the glass surface and the
    surrounding air, if that heat is not being radiated away as quickly as with
    the older design ?
    Plus I did say earlier that the socket was replaced fairly recently, and is
    working just fine again now without one of those bulbs in it.

    Here is a picture of the actual item so you will now know for ever, what a
    UK bayonet cap looks like !

    http://www.comparestoreprices.co.uk...yonet-cap-lightbulb-glass-pearl-pack-of-4.jpg

    and here's one on a CFL. which shows the connection pads very clearly.

    http://upload.wikimedia.org/wikipedia/commons/b/bc/Lightbulb-Bayonet-Cap.jpg

    The B&Q bulb got hot enough to fry that black resin stuff, and completely
    destroy one of the connector pads which are made from (lead-free now, I
    guess) solder.

    Arfa
     
  4. Arfa Daily

    Arfa Daily Guest

    Hi Dave
    I haven't measured the actual power consumption of the new bulbs. A few
    years ago, I would have been surprised if the figure quoted on a lamp was
    not at least within say 5% accuracy, but these days, with the reduction in
    integrity of just about everything, and the fact that much manufacturing is
    now done in 'emerging' industrial countries, I would be less sure of that.
    As to whether the new bulb's envelope is small enough to reduce the
    dissipation of the heat by the amount noted, I'm not really a good enough
    theoretical physicist to make a call of any real value, but given that this
    appears to be the only mechanism by which this could be happening, I would
    have to say that is probably the answer.

    I don't dispute what has been said about 60 watts being 60 watts, or that
    heat and temperature are not the same thing. However, radiation efficiency
    is key to the relationship between the two, as we both know. A 60 watt amp
    with a small silver heatsink on its output transistors will not get rid of
    the unwanted heat anything like as well as if that heatsink is black, and
    force air cooled.

    For all I know, my bench lamp may be a 'special case', and the fitting of
    the smaller bulb might just screw up the dynamics of the air circulation
    within the shade. As anyone who knows the Terry's Anglepoise will agree, the
    shade is not particularly well ventilated. Perhaps it would benefit from
    having a ring of 5mm holes drilled around its top ... ??

    Arfa
     
  5. Arfa Daily

    Arfa Daily Guest


    The things I do for science !! I just had to rootle thru' the workshop bin
    to locate the bulb which caused all the trouble in the first place. It is
    clearly marked 60 watts, and has a CE approval also. I can't tell you what
    the energy rating letter is, as I don't have any more on the shelf. I have
    two other types from the same stable, and one of the boxes has an energy
    rating on it, and one doesn't, so I'll have to look next time I am in the
    store.

    OK. On the diameters. Consider them for all practical purposes, to be a
    sphere. The old was 60mm almost exactly, and the new, 50mm almost exactly,
    measured with an electronic calliper, so reasonably accurate figures.

    Arfa
     
  6. Arfa Daily

    Arfa Daily Guest

    The R80 sounds the way to go from all angles. I'll pick one up next time I'm
    in B&Q

    Arfa
     
  7. Mr. Land

    Mr. Land Guest

    Ah, you see, what you really need is something that'll automatically
    sense when the lamp is on, and turn on a cooling fan. I have just the
    circuit... %^)
     
  8. Arfa Daily

    Arfa Daily Guest

    Quit complainin' !! I'm helping you figure all about light bulbs with my
    question .... :)

    Arfa
     
  9. Arfa Daily

    Arfa Daily Guest



    Peter, Andrew. Thanks for your input. Both good thoughts.

    Arfa
     
  10. Arfa Daily

    Arfa Daily Guest


    I was in the store today, and had a look at the boxes these bulbs are in.
    There is no mention at all of them being a halogen type, but all of the ones
    that are genuinely halogens, do say so. The energy rating on the box was "E"

    Arfa
     
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