Tuesday, 30 August 2022

Another high quality piece of engineering from GM4FVM

As Homer and Marge Simpson once sang in a duet ...

"Do a half assed-job -- it's the American way"

Most US products I have are quite well made, so I doubt if that is true.

However, I am following one of Homer Simpson's examples when it comes to warning lights.

Homer used to be bothered by the warning lamp on his car dashboard. So he cut off a piece of insulating tape and stuck it over the warning. After that he could drive about untroubled.

When I made control boxes for my sequencers I ran out of green LED panel lights. These simply show that power is heading for the masthead preamp, but they are very useful for fault finding. Really, they should be green, but when I ran out of green ones I used red ones, and then I ran out of red ones too.

Solution - repurpose an LED lamp intended for a non-radio project. Sadly this was white and very bright, even from the back of the shelving where these things live. 

I made a note to put a higher value resistor in circuit to get the illumination level down a bit.

Fast forward to now and I have other things to do. So I have adopted the Homer Simpson solution. I have stuck a piece of red insulating tape over the white LED. Wonderful. I now have a pleasant low intensity red glow. 

Homer used opaque black tape, I used slightly transparent red wonder tape so that some light might escape. I have finessed his great idea.

1296MHz sequencer at GM4FVM now with red insulating tape "lens"
I have of course done a full risk-assessment of this user-initiated modification of a user designed and built module. There seems to be no apparent heat present which might shorten the life of the adhesive on the new "colourised self-attached lens substitute" as I now call it. I do not have a full data sheet on the red tape, but as I have had that tape for about 15 years I think it can be used under "grandfather rights". The critical fail state would occur if the tape falls off and the corrective action would be to stick in back on again. The critical consequences of failure would appear to be quite small.

If it does fail I can always take it back to the Maplin shop in Dalry Road in Edinburgh and get my money back [it closed years ago Jim].

I suppose I could trim the tape up to precisely fit the LED surround. Hey, that is a further task to be scheduled for some time in the future.

What a pity that I had already used up all the green tape in that Maplin package. Maybe I should nip down to Edinburgh (2 hours each way in the bus) and buy some more.

Now, off for my next challenging job.



1 comment:

  1. Hi Jim,
    I have some spare green LEDs, what size do you need? 'Standard' or 'min'i? I'll email you to discuss which ones you want. Cheers - Dave (G0DJA)