# OpAmp circuit for temp sensing using diodes

#### Elerion

##### Member
But what you could start with is an ordinary inverting op amp stage, with just two resistors. See if you can develop the formula we all know and love:
Vout=-Vin*R2/R1
Sure I can. That's easy.

I could probably show you a method that you could pick up in a few minutes.
I'd appreciate that
I usually enjoy doing some maths.
Just a few guidelines, can be very helpful to me.

#### MrAl

##### Well-Known Member
Most Helpful Member
Sure I can. That's easy.

I'd appreciate that
I usually enjoy doing some maths.
Just a few guidelines, can be very helpful to me.

Hi again,

I appreciate your interest here.

Do you know about Nodal analysis yet or would like a few pointers?
For example, one of the key points is that the sum of currents into a node is equal to zero.

#### Elerion

##### Member
Yes, I know the theory. I've solved simple circuits. This one seems a bit harder
Just a few pointers about the steps for this particular circuit is good enough. I can do the calculations.
Thanks!

#### MrAl

##### Well-Known Member
Most Helpful Member
File lost in a cab in Bayonne NJ. Next day, I recall buying a Time Sinclair 1000 during a fleeting visit to NY.

A new world of marvels did start that day!
Hello again,

I seem to have overlooked what you said about Bayonne NJ as the Timex Sinclair stuck in my head.
I didnt realize you were that close to me, if you still are. I am in Central NJ near Middlesex. That's maybe 30 miles or so from Bayonne.

#### MrAl

##### Well-Known Member
Most Helpful Member
Yes, I know the theory. I've solved simple circuits. This one seems a bit harder
Just a few pointers about the steps for this particular circuit is good enough. I can do the calculations.
Thanks!
Hello,

Well we can start with an inverting op amp circuit with just two resistors.
Replace the op amp with a voltage controlled voltage source with high gain, typically 100000 but we can make that infinite too.
Have you done any circuit with a voltage controlled voltage source (VCVS) yet? That's a dependent source.

#### atferrari

##### Well-Known Member
Hello again,

I seem to have overlooked what you said about Bayonne NJ as the Timex Sinclair stuck in my head.
I didnt realize you were that close to me, if you still are. I am in Central NJ near Middlesex. That's maybe 30 miles or so from Bayonne.
Hola MrAl,

I spent just three days there with our vessel (tanker) discharging at Bayonne Terminal. Not sure when but maybe one year after the Timex 1000 appeared in the market.

The voyage started in Greece where we took over from the previous crew and loaded later in Arzew for Bayonne.

With my precious Timex, during the voyage back to Buenos Aires I learnt BASIC. Little after I wrote my first serious program to calculate by moments, the trim / drafts of the vessel based on weight distribution.

Until then, that calculation was done by hand or using the Loadicator (if the vessel had one installed). It took me some time to understand that it was, no more nor less than an analog computer. Huge amount of op amps, very warm when in use and incredibly precise.

Two years later, a technician from Radio Holland, coming from Miami to Curaçao, brought me a book by Ronday Zaks where I learnt about the Z80. A new fascinating chapter started with my Timex 2068 doing all kind of strange things.

Digressing, you say? Sure.

#### schmitt trigger

##### Well-Known Member
Atferrari:
Si quieres conocer el mundo sin dinero, marinero.

I am sure that you, like many merchant mariners of the day, have hundreds of anecdotes and stories about your time at sea and while visiting ports all over the world.
I am jealous!

Nowadays I am told (please confirm) that container ships load and unload so quickly that port calls are very brief. In some instances the crew doesn’t even disembark.

#### atferrari

##### Well-Known Member
Atferrari:
Si quieres conocer el mundo sin dinero, marinero.

I am sure that you, like many merchant mariners of the day, have hundreds of anecdotes and stories about your time at sea and while visiting ports all over the world.
I am jealous!

Nowadays I am told (please confirm) that container ships load and unload so quickly that port calls are very brief. In some instances the crew doesn’t even disembark.
Didn't know that saying. Something that people tend to ignore is the time you actually spend at sea. In my case, in 17 years, I spent the equivalent of more than 10 years sleeping in a vessel obviously far from family / friends. As a naval architect working in the same company used to say: the worst is that family gets used to no count on you for anything.

Yes, stories about things that for most of people are unusual or strange. You get used to deal with foreigners, being a foreigner yourself. And sometimes having to suffer ill treatment from the local people. Or just being not allowed to go ashore even with vessel in port.

And then, vessels with mixed nationalities. The record I have seen 15 people and 14 nationalities.

Not only container vessels, general cargo, LPG carriers even bulk carriers go quite fast. I also believe that the mentality of people going at sea has changed. Red-light districts in most of the ports have disappeared. And that started more than 30 years ago.

Besides the contracts for most nationalities are shorter than before, seamen tend to save more, to start something ashore far from vessels. You do not see much old people on board nowadays.

And sometimes, in the middle of nowhere you feel alone. Oh sí.

#### MrAl

##### Well-Known Member
Most Helpful Member
Hola MrAl,

I spent just three days there with our vessel (tanker) discharging at Bayonne Terminal. Not sure when but maybe one year after the Timex 1000 appeared in the market.

The voyage started in Greece where we took over from the previous crew and loaded later in Arzew for Bayonne.

With my precious Timex, during the voyage back to Buenos Aires I learnt BASIC. Little after I wrote my first serious program to calculate by moments, the trim / drafts of the vessel based on weight distribution.

Until then, that calculation was done by hand or using the Loadicator (if the vessel had one installed). It took me some time to understand that it was, no more nor less than an analog computer. Huge amount of op amps, very warm when in use and incredibly precise.

Two years later, a technician from Radio Holland, coming from Miami to Curaçao, brought me a book by Ronday Zaks where I learnt about the Z80. A new fascinating chapter started with my Timex 2068 doing all kind of strange things.

Digressing, you say? Sure.
Hi,

Very interesting with that and also with your voyages. I guess it can have mixed blessings, some good some sad.

I think i got involved with the Z80 before the Timex, but i cant remember that far back now. I crated my own controller board based on the Z80 because microcontrollers were not popular yet. It took a lot of hardware to get that to happen, on a PC board about 4 by 6 inches.

#### schmitt trigger

##### Well-Known Member
That is actually a quote from Javier Bardem in the movie The Sea Inside

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