Some ten years ago,I was approached by a new customer to make a timer
device that can be programmed up to 6 months ahead.When asked for the probable
use for such a device elicited a blank look,I impressed on him the need for a
frank discussion.Finally,it transpired that a foreign outfit was interested
in sourcing long term timer devices for setting off explosions in newly
constructed buildings.I,of course,refused further discussions and turned
him out.I was reminded of some models of AKAI vcrs which sported timer
chips that can be programmed up to 1 year in advance.With suitable external
components,a good technician could have cooked up a device with little
difficulty.Of course,these days,you don't need to delve into bothersome
vcrs to find custom-designed chips.With the advent of PLCs and their
relative ease of programming effort,coupled with the fact that these
devices have been introduced into the high school levels can cause
consternation to the law-abiding citizens.
Apart from the abovementioned nefarious purposes,one can also use
the custom-designed chips,available often at throw away prices,for
any decent household activities,which is the main reason for this
article.
For example, I have used a BA6209 chip (a motor drive ic used in many
vcrs to drive the front loading motors )with a current capability of
1 A,interfaced with a humble 4013 logic chip to trip the power,in
case the motor (which drives a set of reduction gears sourced from
vcrs to close or open curtains) stalled for any reason.The whole idea
was borrowed from a FUNAI VIP 1000 VCP and even after 5 years,the whole
system still works like a song.
I have an assorted switches which can be controlled by the ordinary
TV remote.The Infra red coded pulses operate a multitude of other
"normal" gadgets with these switches sourced from the front end of
many scrapped VCRs.Besides,I have modified a digitron display which
appears in all the vcrs,to show the time and the rpm of a friend's
car engine.The cute little circuit sits in the dash board of the car
and normally displays the time.But on pressing a key,can show the
rpm, in its counter mode.
True,all the above mentioned "gadgets" could have been designed from
the scratch with "logic" circuits or the plcs.But for people like
me,who are steeped in the trade for decades can call upon our favourite
chips to do the job,probably at very little initial outlay.I regret not
to offer suitable schematic diagrams to illustrate some of the ideas
mentioned above.But my intention is to offer the potential of the
replacement chips and their application,entirely different from the
purpose for which they were originally conceived.
