Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out 
Thanks to Alex, I think I now have a better idea of how my humidity control
and logging system will work (thanks for the free electronics ‘refresher
course’ too!). Follow up question: is there any problem driving the four
logic-level FETs off one arduino o/p pin?
Hi Tom,
I have never considered doing that! I’ve always wanted independent control
of each FET. It all depends on how much current it takes to drive the gate
of the FET. I have done a quick simulation and found that if you are
driving the FETS from one pin the current required to drive the gate ON for
four FETS is 20 mA. As the arduino can only source 20 mA from one digital
pin you would over stress the microcontroller and risk damage doing this.
If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.
If that isn’t palatable then you need to choose a microcontroller with more
digital outputs available for your needs. Arduino mega etc…
Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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Thanks Alex.
I wondered if there was something like a 4-output buffer chip or something
- that could propagate TTL levels (I think it’s called fan-out).
I hoped to leave four pins free (the 433mhz radio ties up quite a few
logics) for counting pulses on the fans to get rpms, but this is not so
critical. I also read that only two pins run interrupts, so I have to add
some logic anyway, if not to miss transitions. … I just want a relatively
frequent snapshop of fan RPMs - really just to ensure none of the fans are
stalled or running seriously underspeed.
Thanks for your advice! ~ TomOn 10 July 2014 16:56, Alexander Lang alexanderlang1980@gmail.com wrote:
Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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Tom Shephard (CREST Ltd)
Hi Tom…
It sounds like you are desperately short of digital pins. Are you aware
you can use the analogue pins as digital pins also? To be honest I would
look at an arduino with more pins like the mega 2560 or similar. It would
be interesting to see what exactly your pin count is by the way so I can
help with solutions.
The fan out device you are referring to is a shift register by the
way…you apply three digital pins (clock, data and latch and it allows to
drive eight more outputs, if you are using the device I normally favour
(74HC795). These are readily available and we have some in the hackspace if
you are desperate. I wrote a blog post explaining their usage a long time
ago…
Anyway…here is another option which is a tad unconventional and
physically untested however it simulates well enough and so in theory
should work…
Grab an N-type JFET - yet again we have some in the space…I suggest the
2n5484 or similar. If you look up the datasheet it should be able to
source at lest 20 mA without getting too hot. You then use this JFET to
drive all of the other N-Type MOSFETS at once only using one arduino
pin…I’m simulating this using the interactive DC voltage source V1 in
the diagram this would be replaced by the digital pin from your
arduino…according to the simulation it works! If you like I can upload
a video of the simulation in action…
Cheers
AlexOn 10 July 2014 17:20, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
Thanks Alex.
I wondered if there was something like a 4-output buffer chip or something
- that could propagate TTL levels (I think it’s called fan-out).
I hoped to leave four pins free (the 433mhz radio ties up quite a few
logics) for counting pulses on the fans to get rpms, but this is not so
critical. I also read that only two pins run interrupts, so I have to add
some logic anyway, if not to miss transitions. … I just want a relatively
frequent snapshop of fan RPMs - really just to ensure none of the fans are
stalled or running seriously underspeed.Thanks for your advice! ~ Tom
On 10 July 2014 16:56, Alexander Lang alexanderlang1980@gmail.com wrote:
Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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Tom Shephard (CREST Ltd)–
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What sort of .mutant fet requires that much drive current? Usually they are
very high input impedance therefore usually in the microamp region.On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:
Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the Google Groups
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I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually they
are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap… but
felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the Google
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On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually they
are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots of
hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap…
but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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Tom Shephard (CREST Ltd)
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually they
are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots
of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap…
but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the Google
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Tom Shephard (CREST Ltd)
Tom Shephard (CREST Ltd)
You are using an IRF530 which is a P-type Mosfet. Change the model to an
IRF540 and you should see the correct output.
Cheers
AlexOn 28 July 2014 12:09, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually they
are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a shift
register or other device to drive the gate of the FETS and that way you
only get more outputs sacrificing only three digital pins from the arduino
(gaining 8 outputs) all of which will be capable of driving a FET. You
still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller with
more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots
of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap…
but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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D’oh! … remembering now… I lazily picked the closest model number
(IRF540 doesn’t appear in the list of FETs) thinking the 530 would be most
alike (but didn’t bother to check!). I would ideally like to model with an
IRF630 anyway, as that’s the FET I’ve got in front of me 
I found a colection of Spice models at:
http://www.gunthard-kraus.de/Spice_Model_CD/Vendor%20List/Spice-Models-collection/
-
where ‘pwrmos.lib’ contains the model(s) I want. This is for OrcCad
(apparently), but I’ve read that LtSpice can convert from OrcCad… only
trouble is my copy of LtSpice throws an error when trying to open the
library - ?? -
Charz, TomOn 28 July 2014 12:53, Alexander Lang alexanderlang1980@gmail.com wrote:
You are using an IRF530 which is a P-type Mosfet. Change the model to an
IRF540 and you should see the correct output.Cheers
Alex
On 28 July 2014 12:09, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually
they are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a
shift register or other device to drive the gate of the FETS and that way
you only get more outputs sacrificing only three digital pins from the
arduino (gaining 8 outputs) all of which will be capable of driving a FET.
You still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller
with more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and lots
of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long gap…
but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
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Tom Shephard (CREST Ltd)
Tom,
It has been a while since I played with LT spice. I will take a look when
I get home and see how to sort out a spice model for the IRF630. To be
honest as long as the FET has a VGS on threshold less that 5 V it will work
in your application.
Cheers
AlexOn 28 July 2014 16:28, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
D’oh! … remembering now… I lazily picked the closest model number
(IRF540 doesn’t appear in the list of FETs) thinking the 530 would be most
alike (but didn’t bother to check!). I would ideally like to model with an
IRF630 anyway, as that’s the FET I’ve got in front of meI found a colection of Spice models at:
http://www.gunthard-kraus.de/Spice_Model_CD/Vendor%20List/Spice-Models-collection/
where ‘pwrmos.lib’ contains the model(s) I want. This is for OrcCad
(apparently), but I’ve read that LtSpice can convert from OrcCad… only
trouble is my copy of LtSpice throws an error when trying to open the
library - ??Charz, Tom
On 28 July 2014 12:53, Alexander Lang alexanderlang1980@gmail.com wrote:
You are using an IRF530 which is a P-type Mosfet. Change the model to an
IRF540 and you should see the correct output.Cheers
Alex
On 28 July 2014 12:09, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually
they are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a
shift register or other device to drive the gate of the FETS and that way
you only get more outputs sacrificing only three digital pins from the
arduino (gaining 8 outputs) all of which will be capable of driving a FET.
You still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller
with more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and
lots of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long
gap… but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my humidity
control and logging system will work (thanks for the free electronics
‘refresher course’ too!). Follow up question: is there any problem
driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the Google
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Hi Tom,
I have managed to simulate your circuit above using LT Spice and an IRF630
spice model. I couldn’t find the lamp object though…Please bear with me
it has been a very long time since I tried to use LT Spice. The key points
are that you need to add the required spice model to your library folder
and then change the value of the component you fitted. I followed the
instructions for from this site:
http://adamsiembida.com/adding-spice-models-to-ltspice/#tldr
Can you let me know where you found the lamp symbol…
Good Luck
Alex
[image: Inline images 2]
[image: Inline images 1]On 28 July 2014 16:47, Alexander Lang alexanderlang1980@gmail.com wrote:
Tom,
It has been a while since I played with LT spice. I will take a look when
I get home and see how to sort out a spice model for the IRF630. To be
honest as long as the FET has a VGS on threshold less that 5 V it will work
in your application.Cheers
Alex
On 28 July 2014 16:28, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
D’oh! … remembering now… I lazily picked the closest model number
(IRF540 doesn’t appear in the list of FETs) thinking the 530 would be most
alike (but didn’t bother to check!). I would ideally like to model with an
IRF630 anyway, as that’s the FET I’ve got in front of meI found a colection of Spice models at:
http://www.gunthard-kraus.de/Spice_Model_CD/Vendor%20List/Spice-Models-collection/
where ‘pwrmos.lib’ contains the model(s) I want. This is for OrcCad
(apparently), but I’ve read that LtSpice can convert from OrcCad… only
trouble is my copy of LtSpice throws an error when trying to open the
library - ??Charz, Tom
On 28 July 2014 12:53, Alexander Lang alexanderlang1980@gmail.com wrote:
You are using an IRF530 which is a P-type Mosfet. Change the model to
an IRF540 and you should see the correct output.Cheers
Alex
On 28 July 2014 12:09, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup <watercrestuk@gmail.com wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually
they are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have never considered doing that! I’ve always wanted independent
control of each FET. It all depends on how much current it takes to drive
the gate of the FET. I have done a quick simulation and found that if you
are driving the FETS from one pin the current required to drive the gate ON
for four FETS is 20 mA. As the arduino can only source 20 mA from one
digital pin you would over stress the microcontroller and risk damage doing
this.If you are short of digital output pins I would look at using a
shift register or other device to drive the gate of the FETS and that way
you only get more outputs sacrificing only three digital pins from the
arduino (gaining 8 outputs) all of which will be capable of driving a FET.
You still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller
with more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and
lots of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long
gap… but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my
humidity control and logging system will work (thanks for the free
electronics ‘refresher course’ too!). Follow up question: is there any
problem driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the Google
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FET driver.asc (1.09 KB)
That’s great Alex. Thank you. Am out right now but will check where the
lamp model came from soon; when I get back. Cheers!On 28 Jul 2014 22:44, “Alexander Lang” alexanderlang1980@gmail.com wrote:
Hi Tom,
I have managed to simulate your circuit above using LT Spice and an IRF630
spice model. I couldn’t find the lamp object though…Please bear with me
it has been a very long time since I tried to use LT Spice. The key points
are that you need to add the required spice model to your library folder
and then change the value of the component you fitted. I followed the
instructions for from this site:http://adamsiembida.com/adding-spice-models-to-ltspice/#tldr
Can you let me know where you found the lamp symbol…
Good Luck
Alex
[image: Inline images 2]
[image: Inline images 1]On 28 July 2014 16:47, Alexander Lang alexanderlang1980@gmail.com wrote:
Tom,
It has been a while since I played with LT spice. I will take a look
when I get home and see how to sort out a spice model for the IRF630. To
be honest as long as the FET has a VGS on threshold less that 5 V it will
work in your application.Cheers
Alex
On 28 July 2014 16:28, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
D’oh! … remembering now… I lazily picked the closest model number
(IRF540 doesn’t appear in the list of FETs) thinking the 530 would be most
alike (but didn’t bother to check!). I would ideally like to model with an
IRF630 anyway, as that’s the FET I’ve got in front of meI found a colection of Spice models at:
http://www.gunthard-kraus.de/Spice_Model_CD/Vendor%20List/Spice-Models-collection/
where ‘pwrmos.lib’ contains the model(s) I want. This is for OrcCad
(apparently), but I’ve read that LtSpice can convert from OrcCad… only
trouble is my copy of LtSpice throws an error when trying to open the
library - ??Charz, Tom
On 28 July 2014 12:53, Alexander Lang alexanderlang1980@gmail.com wrote:
You are using an IRF530 which is a P-type Mosfet. Change the model to
an IRF540 and you should see the correct output.Cheers
Alex
On 28 July 2014 12:09, CREST CharltonRiverGroup <watercrestuk@gmail.com wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup < watercrestuk@gmail.com> wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually
they are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” < alexanderlang1980@gmail.com> wrote:Hi Tom,
I have never considered doing that! I’ve always wanted
independent control of each FET. It all depends on how much current it
takes to drive the gate of the FET. I have done a quick simulation and
found that if you are driving the FETS from one pin the current required to
drive the gate ON for four FETS is 20 mA. As the arduino can only source
20 mA from one digital pin you would over stress the microcontroller and
risk damage doing this.If you are short of digital output pins I would look at using a
shift register or other device to drive the gate of the FETS and that way
you only get more outputs sacrificing only three digital pins from the
arduino (gaining 8 outputs) all of which will be capable of driving a FET.
You still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller
with more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and
lots of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long
gap… but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my
humidity control and logging system will work (thanks for the free
electronics ‘refresher course’ too!). Follow up question: is there any
problem driving the four logic-level FETs off one arduino o/p pin?–
You received this message because you are subscribed to the
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Tom Shephard (CREST Ltd)–
Tom Shephard (CREST Ltd)–
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https://groups.yahoo.com/neo/groups/LTspice/files/%20Lib/Electrical%20Lamp/On 28 July 2014 22:50, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
That’s great Alex. Thank you. Am out right now but will check where the
lamp model came from soon; when I get back. Cheers!
On 28 Jul 2014 22:44, “Alexander Lang” alexanderlang1980@gmail.com wrote:Hi Tom,
I have managed to simulate your circuit above using LT Spice and an
IRF630 spice model. I couldn’t find the lamp object though…Please bear
with me it has been a very long time since I tried to use LT Spice. The
key points are that you need to add the required spice model to your
library folder and then change the value of the component you fitted. I
followed the instructions for from this site:http://adamsiembida.com/adding-spice-models-to-ltspice/#tldr
Can you let me know where you found the lamp symbol…
Good Luck
Alex
[image: Inline images 2]
[image: Inline images 1]On 28 July 2014 16:47, Alexander Lang alexanderlang1980@gmail.com wrote:
Tom,
It has been a while since I played with LT spice. I will take a look
when I get home and see how to sort out a spice model for the IRF630. To
be honest as long as the FET has a VGS on threshold less that 5 V it will
work in your application.Cheers
Alex
On 28 July 2014 16:28, CREST CharltonRiverGroup watercrestuk@gmail.com wrote:
D’oh! … remembering now… I lazily picked the closest model number
(IRF540 doesn’t appear in the list of FETs) thinking the 530 would be most
alike (but didn’t bother to check!). I would ideally like to model with an
IRF630 anyway, as that’s the FET I’ve got in front of meI found a colection of Spice models at:
http://www.gunthard-kraus.de/Spice_Model_CD/Vendor%20List/Spice-Models-collection/
where ‘pwrmos.lib’ contains the model(s) I want. This is for OrcCad
(apparently), but I’ve read that LtSpice can convert from OrcCad… only
trouble is my copy of LtSpice throws an error when trying to open the
library - ??Charz, Tom
On 28 July 2014 12:53, Alexander Lang alexanderlang1980@gmail.com wrote:
You are using an IRF530 which is a P-type Mosfet. Change the model to
an IRF540 and you should see the correct output.Cheers
Alex
On 28 July 2014 12:09, CREST CharltonRiverGroup < watercrestuk@gmail.com> wrote:
LtSpice simulation of the FET cct… Seems to work but the output is
inverted.On 28 July 2014 12:07, CREST CharltonRiverGroup < watercrestuk@gmail.com> wrote:
On 10 July 2014 20:09, Alexander Lang alexanderlang1980@gmail.com wrote:
I just chose IRF540’s because I know that the model for them is
accurate…and those are the numbers that the simulator spat out…Fee free
to choose a more suitable FET that provides the required current and have a
low (logic level) VGS on thresholdand also provide the required drain
source current without dissipating too much heat and melting their way off
the board.On 10 July 2014 19:55, Ben Dooks bjdooks@googlemail.com wrote:
What sort of .mutant fet requires that much drive current? Usually
they are very high input impedance therefore usually in the microamp region.
On 10 Jul 2014 16:56, “Alexander Lang” < alexanderlang1980@gmail.com> wrote:Hi Tom,
I have never considered doing that! I’ve always wanted
independent control of each FET. It all depends on how much current it
takes to drive the gate of the FET. I have done a quick simulation and
found that if you are driving the FETS from one pin the current required to
drive the gate ON for four FETS is 20 mA. As the arduino can only source
20 mA from one digital pin you would over stress the microcontroller and
risk damage doing this.If you are short of digital output pins I would look at using a
shift register or other device to drive the gate of the FETS and that way
you only get more outputs sacrificing only three digital pins from the
arduino (gaining 8 outputs) all of which will be capable of driving a FET.
You still get independent control and you have more outputs available.If that isn’t palatable then you need to choose a microcontroller
with more digital outputs available for your needs. Arduino mega etc…Here is a link to my blog by the way with details about FETS and
lots of hopefully helpful other information…http://langster1980.blogspot.co.uk/2012/09/using-field-effect-transistors.html
http://langster1980.blogspot.co.uk/
cheers
Alex
On 10 July 2014 14:15, Tom Shephard watercrestuk@gmail.com wrote:
Popped into the space last night after an embarrassingly long
gap… but felt very thankful that I was immediately helped out
Thanks to Alex, I think I now have a better idea of how my
humidity control and logging system will work (thanks for the free
electronics ‘refresher course’ too!). Follow up question: is there any
problem driving the four logic-level FETs off one arduino o/p pin?–
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Tom Shephard (CREST Ltd)
