Re: Another Great Amplifier Design...

On a sunny day (14 Aug 2006 10:32:19 -0700) it happened "Telstar Electronics"
<briangriffey@xxxxxxxxxxxxx> wrote in
<1155576739.654369.113000@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

I was never able to deciper your drawing exactly. However, from what I
make of it ... I have a few problems with it... as I understand it. The
first problem is that your source is not regulated.

The LED is the regulator / reference voltage.
LEDs have 1.5 volt across them (or some slightly higher voltage, depending
on the type of LED) independent of the current.
The LED gets the current from the +12V via a resistor.

Don't think that's
a good plan as that could grossly impact the threshold point at best.

Nope, it is very stable, opamps are independent of the power supply,
it is called supply rejection and common mode rejection.

The second problem is there is no hysterisis at the threshold point.

There is in fact, it is in the _relay_.
In the case of the thyristor (or SCR) when it switches it is BOOM and
no need for hysterical thesis. oops.

If
the sink got close to the trip point... the relay would chatter would
drive you nuts.

Well, no way, have you tried?
And you would also like to _do_ something with that relay, like using
a break contact to cut power, and once it is off an other make contact
to change the reference voltage so it stays there... relays are nice.

The idea about the SCR is also not palatable to me. I
don't want to blow a fuse when a fault is detected. Blowing the fuse is
undesireable because the amplifier is out of commission until the fuse
is replaced.

Better the fuse then the 'pills', and it will have the customer look for
the problem (hopefully), but you are right, I have had stuff here with the
fuse replaced by a big nail.... :-)

Not the best for making the customer happy... LOL. I want
a shut-down mode that will completely restore amp operation when the
fault (heat or excessive SWR) is gone. What I described earlier will
accomplish that spec.

So does the relay, you COULD provide a reset button, but what I do not want
is them running it with tripping the protection every few minutes...
people do that too.
Ad a indicator LED or light,

'Temperature exceeded,
check for obstructions
in air flow or defective fan'

Add a nice LCD display (2 line I have here with green LED backlight),
a PIC microprocessor to display some texts, and when you use the micro you
can use the PIC comparator or AD to monitor the temp sensor, and program it
any way you want.
I used the PIC in my lightning detector too, these cost only 2$ and you can
modify software without making new boards.


Thanks for your input... it's a pleasure to talk to someone on this NG!

Well, I make little cicuits sometimes, been doing it all my life....
It is fun, also I find your designs interesting, looked at that PCB layout
for a long time, was wondering if you used silver plated wire or litze.

Never too old to learn :-)

.

Relevant Pages

  • Re: burned out element detection
    ... a burden resistor, a current limiting resistor and a LED for ... so it required no power source - the CT's powered the LEDs. ... I can use a current transformer to drive a low-power relay, ...
    (sci.electronics.design)
  • Re: 240v mains to logic output?
    ... I would recommend incorporating a local quick blow very low rated fuse on the mains side. ... Your typical 6A breaker or 6-13A heating fuse will blow your board to bits before the fuse clears the fault. ... There are optos with two LEDs in there, takes care of the reverse diode and covers both half-waves with very little gap. ... are set up to verify it can't track), so why not extend your original idea and build an optoisolator with a large air gap - LED at one end of a piece of black plastic tube, photo-thingy at the other... ...
    (sci.electronics.design)
  • Re: surges slowly destroying
    ... Obviously, only BLUE LEDs contain any kind of magic, because all the most ... There were 16 different fuse holders ... with a big neon indicator light that stayed lit while it was plugged in. ...
    (sci.electronics.repair)
  • Re: ST:TNG "Check fuses 114 and 115"
    ... Your fuse message, the symptoms you describe and the LEDs that aren't ... it's likely with a melted coil that you have at least a bad driver on ...  Sure enough the under diverter bottom was jammed and I ...
    (rec.games.pinball)
  • Re: Fitting a relay.
    ... upset the warning system. ... Trouble is a relay will slow down the LEDs ... parallel resistor on the input to set the trigger current. ...
    (uk.rec.cars.modifications)