A spot of
nostalgia
Techno Talk
Mark Nelson
Sorry to disappoint; there are no April Fool items to spot in this month’s article. But you are guaranteed
your normal diet of the weird and wonderful in the world of fairly practical electronics. Something old,
something new and maybe even something blue. So let’s crack on with it. Or as WC Fields used to say,
‘Start the day with a smile – and get it over with’.
L
et’s begin with the first of two
trips down memory lane in this
month’s sermon. Do you remember Tandy shops? Derided by some,
Tandy often saved my bacon, mainly
because being disorganised, I frequently ran out of components at
awkward times, such as 5pm on a
Saturday afternoon (not ideal if you
have set Sunday aside for constructing an electronic project). Panic not;
there was still just enough time to
dash over to my nearby Tandy emporium and pick up a blister pack of
a dozen 10kΩ resistors or a hank of
solder. No matter that these cost me
more than they ought to; paying over
the odds avoided the frustration and
disappointment of a wasted Sunday.
Eventually the convenience of nipping out to a local electronics shop
came to an end, when Tandy shops
closed in 1999, having been bought
by Carphone Warehouse to be reborn
either as cellphone shops or else as
Tecno camera outlets. The trading
name was revived subsequently by
new owners and now operates online
at www.tandyonline.com
Maplin, backwards and forwards
All was not lost when Tandy shops disappeared, as larger and slicker Maplin
Electronics shops took up the slack in
the retail vacuum created. Although
highly successful for four decades, with
217 Maplin stores in mid-2017, the
business suffered from online competition and on 25 June 2018, all Maplin
stores ceased trading after failing to
find a buyer for the business. The name
was revived by new owners in January
2019, with a Maplin website brought
back online. Amusingly, a rival operation opened with the reversed name
of ‘Nilpam’, but currently the https://
nilpam.uk website merely states ‘We’ll
be back soon’.
Battery bonus
Tandy had an enterprising gimmick
for regular customers in the form of
their Tandy Battery Club. The sales
10
staff would offer you a loyalty card
that entitled you to one free AA, C, D
or PP3 cell a month when you bought
something in their shop (probably
some more batteries, as a single AA,
C or D cell was seldom of use on its
own; whereas the Power Pack was
viable of course). However, you get
what you ‘pay’ for and the quality
of these batteries was not very good;
likewise the free fl ashlight torches
that they sometimes gave away. I did
wonder how many people had more
than one Battery Club card on the go
at once... No matter.
Talking of batteries brings me to an
environmentally friendly means of recycling them, mooted by Julien Leclaire
at the University of Lyon in France. For
decades, scientists in Lyon have tried
to find a use for atmospheric carbon
dioxide and now the Agchemigroup.
eu blog reports that the researchers at
Lyon have discovered that CO2 can
be used to extract useful metals from
discarded batteries. The breakthrough
helps solve two major problems: reducing greenhouse gas emissions from
industry and the waste of raw materials that could be recycled.
Leclaire’s team has devised a process for extracting useful metals from
recycled technology, such as smartphone batteries. Not only would this
help solve the problem of toxic metals
leeching into ground water at landfill
sites, but it could also provide a practical source of the dwindling supplies of
rare-earth elements used in high-tech
electronic products, not to mention
other raw materials. Says Leclaire, ‘By
simultaneously extracting metals and
injecting CO2, you add financial value
to a process that is known to be costintensive.’ You can read an abstract
of the technology involved at: https://
go.nature.com/39PROuJ
Sausages past and present
Now for our second look back in time
– to 1979 and the BBC television programme That’s Life. This featured
Prince, a talking dog that loved ‘talking’
about his favourite food, sausages.
There’s a clip online of this clever creature at: https://youtu.be/ajsCY8SjJ1Y.
Talking of vintage sausages, I noticed
that one of my 12V ‘wall wart’ power
supplies has a small sausage-like object incorporated in the output lead.
Yes, I know that it’s some kind of ferrite
suppressor for stopping any RF hash
generated by the switch-mode power
supply (SMPS) entering whatever device the power supply is feeding, but
why don’t you see these suppression
sleeves much nowadays?
According to the Internet (which
must be right), the ferrite core acts
as a one-turn common-mode choke,
and can be effective in reducing conducted and/or radiated emissions
from the cable, as well as suppressing
high-frequency pick-up in the cable.
Basically, ferrites can be thought of as
high-frequency resistors, having little
or no impedance at low frequencies
or DC. Ferrite cores are most effective
in providing attenuation of unwanted
noise signals above 10MHz.
So why were they necessary in the
past but not now? It could be that
the SMPS of today does not generate
as much hash as in days gone by. Or
perhaps it’s just a sign of cheapskate
cost-cutting – sorry, intelligent value
engineering in China’s factories. Reader
feedback on this conundrum would be
very welcome. I note that the subject
has come up on an online forum, with
some amusing responses. For instance:
‘I once bought a replacement charger
for my Lenovo laptop from China. I
found that the suppressor was a dummy. The Chinese manufacturer wasn’t
hampered by some silly-ass regulator.’ Also: ‘Modern cables tend to be
shielded and so a lot of cables don’t
really need these.’
Really? The output cable from a
SMPS is always made of normal unshielded wire in my experience. Maybe
the suppression components are all
placed inside the SMPS nowadays,
but I have never seen any inside the
wall warts that I’ve torn apart.
Practical Electronics | April | 2020
