How about it? Experiments of the third kind , take 999999.

[Jan Panteltje]

How about it? Experiments of the third kind , take 999999.
Update
Hotplate design,
stabilizing the heater MOSFET

http://panteltje.com/pub/thermos_box_mounting_plus_heater_circuit_diagram_IMG_3415.JPG
shows the quick sketch diagram of the MOSFET driver.
The idea is that the current through the MOSFET is exactly proportional to the input voltage.
As we all know, MOSFETs like to do their thing too,
and in such a configuration like to sing (oscillate).
And so also this circuit.

Playing with it and the oscilloscope a bit did lead to this very quiet circuit,
that within a fraction of a millivolt has the MOSFET drain current follow the input.
There were 2 issues here, 1) MOSFET likes to oscillate, and 2) opamp too.
So sort of separating both from each other worked.

+4V
R1 |
470k + |------
---===--------------|\ 100k 1k |--- |
| | - | >-------===--------===----| |<-- === 1u
control- === ---|/ | |---| |
voltage | 1u | === IRLZ34N | ///
0 to +1 V | C1 | | 1u on |
| /// | TCL274 /// hotplate |
/// | as heater | about 300 mA
-------------------------------------|
|
[ ] 3.3 Ohm
|
///


Having a linear relationship between the control voltage and the output current (power) makes
the software control loop simpler.
Why 1 uF everywhere? I bought a bag of 100.
The 470 K is just for test, this will come from the PIC PWM,
R1 C1 is the lowpass.
100 k and 1k are nice round values.
The 3.3 Ohm was calculated using Ohm law.
The rest ... anyways we need no speed, nowhere in the year long project,
Even outside the black box the hotplate, and so the parts on it, easily meets target
temperature of 40C with about 1,3 W input.
Should be way less watts with it in the black box and thermally insulated on top of that.
As stated before, there will be a 1N4148 diode mounted to the hotplate as temperature sensor.
A PIC microcomputer will do the control loop in software.
Time for pizza (heater is still running).

 

[Tim Williams]

Try a cap from op-amp output to -input, 100pF is enough. Add a series 10k
resistor between this node (-in with cap) and the shunt resistor, so the cap
has something to work into. Get rid of the 100k series resistor and 1uF
filter cap.

As shown, it'll something between oscillate and motorboat, depending on the
position of the planets. The op-amp is an integrator with 90 degree phase
shift, and the RC following it does the same (for a more limited range of
frequencies). 180 degree phase shift at most any frequency means you're
guaranteed to oscillate somewhere.

You might consider making both series input resistors (the 470k control
voltage filter and the shunt voltage feedback) the same value (100k?) so the
input bias (if any) generates a matching offset on both inputs. As a CMOS
amp, offset won't be the greatest (a few mV, plus input offset bias), but if
this is within a temperature control loop, offset and 1/f noise won't be a
problem.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

How about it? Experiments of the third kind , take 999999.
Update
Hotplate design,
stabilizing the heater MOSFET

http://panteltje.com/pub/thermos_box_mounting_plus_heater_circuit_diagram_IMG_3415.JPG
shows the quick sketch diagram of the MOSFET driver.
The idea is that the current through the MOSFET is exactly proportional to
the input voltage.
As we all know, MOSFETs like to do their thing too,
and in such a configuration like to sing (oscillate).
And so also this circuit.

Playing with it and the oscilloscope a bit did lead to this very quiet
circuit,
that within a fraction of a millivolt has the MOSFET drain current follow
the input.
There were 2 issues here, 1) MOSFET likes to oscillate, and 2) opamp too.
So sort of separating both from each other worked.

+4V
R1 |
470k + |------
---===--------------|\ 100k 1k |--- |
| | - | >-------===--------===----| |<-- === 1u
control- === ---|/ | |---| |
voltage | 1u | === IRLZ34N | ///
0 to +1 V | C1 | | 1u on |
| /// | TCL274 /// hotplate |
/// | as heater | about 300 mA
-------------------------------------|
|
[ ] 3.3 Ohm
|
///


Having a linear relationship between the control voltage and the output
current (power) makes
the software control loop simpler.
Why 1 uF everywhere? I bought a bag of 100.
The 470 K is just for test, this will come from the PIC PWM,
R1 C1 is the lowpass.
100 k and 1k are nice round values.
The 3.3 Ohm was calculated using Ohm law.
The rest ... anyways we need no speed, nowhere in the year long project,
Even outside the black box the hotplate, and so the parts on it, easily
meets target
temperature of 40C with about 1,3 W input.
Should be way less watts with it in the black box and thermally insulated
on top of that.
As stated before, there will be a 1N4148 diode mounted to the hotplate as
temperature sensor.
A PIC microcomputer will do the control loop in software.
Time for pizza (heater is still running).

 

[Jan Panteltje]

Try a cap from op-amp output to -input, 100pF is enough. Add a series 10k
resistor between this node (-in with cap) and the shunt resistor, so the cap
has something to work into. Get rid of the 100k series resistor and 1uF
filter cap.

I have tried several configurations, of course the first one that came to mind
is 'integrator' but I had problems with huge oscillation at some input voltages.
After many test I settled for this, as I cannot get it unstable in any way.
I reduced the source resistor to 1.1 Ohm (2 x 2.2 parallel) to get more
of the generated heat into the hotplate.

As shown, it'll something between oscillate and motorboat, depending on the
position of the planets.

The planets seemed favorable today, you will have to show the math why these
should influence - and in what way- the circuit.
I have read about dark energy, but am not that much of a believer,
especially not if it interacts with the electrons in this circuit.
Once someone told be he had a system for the stock market,
and in that system you should buy if this planet went up and the other down,
so I asked him:
Why not this planet down and the other up?
That shorted his neural net enough to drop the idea...

The op-amp is an integrator with 90 degree phase
shift, and the RC following it does the same (for a more limited range of
frequencies). 180 degree phase shift at most any frequency means you're
guaranteed to oscillate somewhere.

The 1k is just a gate resistor to stop the MOSFET from interfering with local FM
and short wave, the 100k isolates the rather low output impedance from
whatever the MOSFET wants to put out on its gate, it is basically a 2 way 'T' filter.

You might consider making both series input resistors (the 470k control
voltage filter and the shunt voltage feedback) the same value (100k?) so the
input bias (if any) generates a matching offset on both inputs. As a CMOS
amp, offset won't be the greatest (a few mV, plus input offset bias), but if
this is within a temperature control loop, offset and 1/f noise won't be a
problem.

The circuit is now like this:
PIC runs on 3V supply, and the PWM switches between 0 and 3V.
With an 1.1 Ohm resistor for 330 mA max (for now, based on previous plastic box
burning test) no more than 600 mV should be at the + input of the TCL274,
making 330 mV about mid range (it can become -5 °C).
This requires a voltage divider of ratio of .6 to (3 - .6) makes .6 to 2.4,
and to not load that opamp I have now 470 k to the PIC PWM output and 120 k to ground,
normal E series, high values preferred so I can use my 1 uF caps.

+4 V
R1 |
470k + |------
---===---------------|\ 100k 1k |--- |
| | | - | >-------===--------===----| |<-- === 1u
0-3V [ ] === --|/ | |---| |
PWM | | 1u | === IRLZ34N | ///
from PIC /// |C1 | | 1u on |
| 120k /// | TCL274 /// hotplate |
/// | as heater | about 300 mA
------------------------------------|
|
[ ] 1.1 Ohm
|
///
These are actually nice opamps, very low offset, typical about a mV,
I measure less, even lower offset drift, 1.8 uV (micro volt) per degree C.
And works all the way to -.2 V common mode range (but not very high upwards).
As in these one supply circuits, having the 0 V as reference is nice.
I will take some peculiarities, already I am having great fun with it.
The opamp output voltage range detoriates fast with any load (say 5 mA).

 

[Tim Williams]

No, like this.
http://webpages.charter.net/dawill/tmoranwms/Circuits_2010/Current_Sink.png
It is easy to show the speed, stability, accuracy and phase margin are
greatly improved. If you cannot show why this is better than the circuit
you've drawn, you shouldn't be working with op-amps at all, do it in
software.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Try a cap from op-amp output to -input, 100pF is enough. Add a series 10k
resistor between this node (-in with cap) and the shunt resistor, so the
cap
has something to work into. Get rid of the 100k series resistor and 1uF
filter cap.

I have tried several configurations, of course the first one that came to
mind
is 'integrator' but I had problems with huge oscillation at some input
voltages.
After many test I settled for this, as I cannot get it unstable in any
way.
I reduced the source resistor to 1.1 Ohm (2 x 2.2 parallel) to get more
of the generated heat into the hotplate.

As shown, it'll something between oscillate and motorboat, depending on
the
position of the planets.

The planets seemed favorable today, you will have to show the math why
these
should influence - and in what way- the circuit.
I have read about dark energy, but am not that much of a believer,
especially not if it interacts with the electrons in this circuit.
Once someone told be he had a system for the stock market,
and in that system you should buy if this planet went up and the other
down,
so I asked him:
Why not this planet down and the other up?
That shorted his neural net enough to drop the idea...

The op-amp is an integrator with 90 degree phase
shift, and the RC following it does the same (for a more limited range of
frequencies). 180 degree phase shift at most any frequency means you're
guaranteed to oscillate somewhere.

The 1k is just a gate resistor to stop the MOSFET from interfering with
local FM
and short wave, the 100k isolates the rather low output impedance from
whatever the MOSFET wants to put out on its gate, it is basically a 2 way
'T' filter.

You might consider making both series input resistors (the 470k control
voltage filter and the shunt voltage feedback) the same value (100k?) so
the
input bias (if any) generates a matching offset on both inputs. As a CMOS
amp, offset won't be the greatest (a few mV, plus input offset bias), but
if
this is within a temperature control loop, offset and 1/f noise won't be a
problem.

The circuit is now like this:
PIC runs on 3V supply, and the PWM switches between 0 and 3V.
With an 1.1 Ohm resistor for 330 mA max (for now, based on previous
plastic box
burning test) no more than 600 mV should be at the + input of the TCL274,
making 330 mV about mid range (it can become -5 °C).
This requires a voltage divider of ratio of .6 to (3 - .6) makes .6 to
2.4,
and to not load that opamp I have now 470 k to the PIC PWM output and 120
k to ground,
normal E series, high values preferred so I can use my 1 uF caps.

+4 V
R1 |
470k + |------
---===---------------|\ 100k 1k |--- |
| | | - | >-------===--------===----| |<-- === 1u
0-3V [ ] === --|/ | |---| |
PWM | | 1u | === IRLZ34N | ///
from PIC /// |C1 | | 1u on |
| 120k /// | TCL274 /// hotplate |
/// | as heater | about 300 mA
------------------------------------|
|
[ ] 1.1 Ohm
|
///
These are actually nice opamps, very low offset, typical about a mV,
I measure less, even lower offset drift, 1.8 uV (micro volt) per degree C.
And works all the way to -.2 V common mode range (but not very high
upwards).
As in these one supply circuits, having the 0 V as reference is nice.
I will take some peculiarities, already I am having great fun with it.
The opamp output voltage range detoriates fast with any load (say 5 mA).

 

[JW]

On a sunny day (Mon, 2 Apr 2012 06:40:32 -0700 (PDT)) it happened George
<[email protected]>:

?????????????????

[snip]

George posted in Base64 for some reason. Here's what it says:

I wrote:

[1] Will report back.

                                                        +4V
                                                         |
       R1                                           ---- |
      470k              +             R2           |     |
PWM ---===----------------|\          100k     |---      |
0-3V       |     |      - | >---------===----| |<--     === 1u
from      [ ]   ===    ---|/    |              |---|     |
PIC   120k |     | 1u  |       ===        IRLZ34N  |    ///
          ///    |     |        | C2       on      |
                ///    | TCL274 | 1u     hotplate  |
                       |        |        as heater | 0-600 mA
                        -------------===-----------|
                                     100k          |
                                     R3           [ ] 1.1 Ohm
                                                   |  R4
                                                  ///

So, I changed some components around a bit,
this seems to work OK over the full range of 0 to 600 mA.

I stayed with the standard capacitors of 1uF, and the standard resistors of 100k.
1k is OK for R2, in that the MOSFET does not detectable oscillate,
but then its 880 pF input capacitance is still felt by the opamp.
As we are slowing down things anyway, 100k is better.

What point size of engraving do you prefer?
Please note there is only 80 mm height available.
Of course we can always change to a bigger box.

Hi Jan, I like the V-I converter. It gives a nice linear relation
between voltage in and power out. Do you stick the 1.1 ohm current
sesnse resistor on the hot plate too? Why not use a BJT for the pass
element?

George H.

 

[Jasen Betts]

On a sunny day (Mon, 2 Apr 2012 06:40:32 -0700 (PDT)) it happened George
<[email protected]>:

?????????????????

looks like GG decided to convert half the spaces to non-breaking spaces
and then base-64 encode the result. base64 wins over Quoted-Printabe
once more than a quarter of the octets are high, and it wouldn't have
been more legible as quoted-printable anyway.

Gotta wonder aboutr the space mangling thoough, mixing normal and
non-breaking spaces is an html trick - there's no need to apply it
to usenet.

 

[Jasen Betts]

Yes I noticed the messed up spaces,
he probably had it in some webbrowser, maybe via google groups.
I did notice the base 64 header, one of those days I fix my newsreader
so it calls base64.
Have not done any changes to it in many years,
so that would take maybe a day to get back into the old code.
Usenet should be just ASCII text, and maybe some binaries attached,
but most ISPs already block binary groups out of fear of copy right
issues.

These days I browse with 'pictures off' in seamonkey,
only when I want to see something do I enable these.
much faster
What worries me is all the lookups to 1.1.1.2 1.1.1.3 etc..
google this google that, facebook, as if they own your computer.
For the adds I just do something like this in /etc/hosts/
10.0.0.190 ad.yieldmanager.com
10.0.0.190 adserver.adtech.de
10.0.0.190 doubleclick.net
10.0.0.190 ajax.googleapis.com
10.0.0.190 connect.facebook.net
10.0.0.190 ......

And 10.0.0.190 is NOT on the LAN, so that comes back really fast with connection refused.
And I have 4444 lines of reject (some whole domains) in iptables too.
Freedom!

net 127/8 is even faster than net 10/8

 

[Jasen Betts]

Sorry, what is that supposed to mean?

loopback is a class A netowrk, you can put all your reject sites into
there somewhere and not need to wait for the ARP requests on the LAN to time out.