In article , David Looser
wrote:
"Jim Lesurf" wrote in message
...
In article , David Looser
wrote:

They do not necessarily clash. By what criterion were they
"expensive"?

The thermal delay relays used were the order of a couple of quid
*each* in quantity, back in the 1970s. Compare that with the few pence
per diode bridge for better diodes that didn't need the delay. Plus of
course the savings to all involved when the change had a quite marked
effect in lowering the numbers being returned for repair because the
thermal delay was unreliable.

You'd expect thermal delay units to be expensive compared to diodes. But
a couple of quid each is cheap for thermal relays.

But still expensive when the - far more reliable - alternative is a few
pence for diodes.


What measurements did you do on the delay unit we are discussing?
And how
many of them did you check, and over what period of time?

Well clearly I made no measurements. I only had one unit to examine and
it had already failed by the time I examined it. But I do understand
how the things work, and have met a number used in different bits of
kit over the years.

So I do know the limitations of the device.

Actually, no, you don't. You saw one and from your own admission judged it
simply on appearance and your general theories about the class of such
devices.

Whereas I at the time had experience of many of the specific devices *and*
did tests to compare them with alternatives, of a range of types/methods.

However I agree with you that such devices do tend to be far less reliable
than designing them out of the system. That is my experimental experience
for a range of types of mechanical switches. Mostly conventional relays,
but also thermal and other forms of sensor driven types. Hence my quoting
the delay as an example of a device relying on mechanical contacts that was
unreliable - and easily replaced by something cheaper and better.

I note your personal opinions. Perhaps you missed some of the things I
wrote. :-)

I don't think I missed any, though you seem to have missed the point
that making judgments on the reliability of electromagnetic relays
based on your experience of an *entirely different* device seems, at
best, hasty!

I agree. Hence my noting that you made no measurements on the specific
device I used as an example, and just judged it on the basis of appearance
and your own general opinions. :-)

You may however have still missed the point that I have also experience
with conventional electrically operated relays in a range of applications.

So I'll stay with my views based on a mix of my experimental experience and
having tried various alternatives. if you prefer electromechanical switches
to solid state alternatives you are welcome to do so. :-)

Slainte,

Jim

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