Stuff that Doesn’t Work

Behind every great inventor, goes the saying, is a pile of failed experiments. Here I’m going to document some of my cases of finding out the hard way what doesn’t work.

Having found a mains transformer with a secondary rated at 12V, 1A in my junk box, I thought this might do for the basis of an inverter to run a compact fluorescent lamp. So it just needs something to drive it.

Using two TDA2030s to build an inverter to run a CFL doesn’t work. Although the left-hand one oscillates quite nicely and the right-hand one inverts it properly, applying a nice square wave across the primarysecondary of the transformer, the output sags hopelessly under load. The output impedance of the TDA2030 is just too high. Where we saw 9V at the transformer secondary and a promising 170V at the primary into an open circuit, this drooped to a pathetic 90V under load. All the lamp managed was a feeble glow.

4 Responses to “Stuff that Doesn’t Work”

  1. For some bizarre reason, i have a mental picture of Lionel Jeffries in a desert trooper outfit singing about ‘roses of success’.

    I’d say that a feeble glow was some victory – better than no light at all and as you say, at least you know not to try that particular way now.

    Your schematic above would make an interesting photo jigsaw!

    Jonathan – Fabulous Photo Gifts.

  2. AJS says:

    I’d say that a feeble glow was some victory – better than no light at all

    Oh, believe me, it was a very sick, feeble glow. Imagine a torch that has been left on all night, only dimmer.

    The schematic was done in GIMP. After spending several hours slaving over a hot soldering iron (and very carefully bending the leads of Pentawatt packages to fit the spacing of Veroboard!), I was too cream crackered to faff about with anything more sophisticated. I didn’t even put the component values on (not much point really, seeing as it doesn’t work).

    On the plus side, it only needs a few bits changing to turn it into an audio amplifier ….. so it’s not a complete loss.

    Now, as for the jigsaw idea, how about a range of interlocking “jigsaw pieces” with schematic symbols on them, that you can fit together in various ways to build circuits?

  3. Ah! Well you’d be talking about a one-off cut pattern, to size, to a template drawing. Not impossible – in fact we have already done a special ‘jig’ order for a business order.

    This one was a rather simpler phrase with the letters cut into a standard 24 piece wooden jigsaw.

    The more detail, the more the cutting ‘jig’ origination cost which has to be passed back to the customer ordering but sometimes it’s still the best option to get exactly what you want.

    Our jigsaws are usually the same cut (allowing for very slight variations between batches) so it has been done before by an art student who wished to put 4 separate jigsaws (4 images) together as one jigsaw – a corner from each jigsaw effectively.

    You have to let us know if that’s what you’re planning though as we’d hate to not check the orientation of the blanks before printing and leave you with jigsaws that don’t fit together in the right sequence. The blanks are not symetrical in that respect.

  4. AJS says:

    For some bizarre reason, i have a mental picture of Lionel Jeffries in a desert trooper outfit singing about ‘roses of success’.

    And now for the obligatory YouTube link:

    Or if you’d rather use youtube-dl instead: http://uk.youtube.com/watch?v=GND10sWq0n0