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LCD (TFT) Heater for low temperatures

Started by EnigmaPaul December 16, 2015
Hi Folks - 

I have an application for low temperature readability of a TFT display.  The challenge I'm facing is that the convention heater options for displays are very expensive for my application (large volume).  An ITO heater adds significant cost to the standard display.

Given that my end product will be housed in a watertight enclosure of a small volume, it will have some internal heating from micro-controllers and other heat generating components.   We'd ideally like to be able to read the display as low as -40C.  The TFT that I'm looking at as an automotive spec and is rated to -30C although the suppliers indicates that it might not be readable at that temp.  We typically update the display content around once per second.  

I'm reaching out to see if others might have some clever workarounds or suggestions for this challenge.

I've often thought about placing power resistors strategically, or using FETs to generate and control heat, but had anyone out there had any success with this?  Here is an old example I found from Electronic Design magazine http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf

My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs.

Thanks!

Paul
On Wednesday, December 16, 2015 at 2:35:20 PM UTC-5, EnigmaPaul wrote:
> Hi Folks - > > I have an application for low temperature readability of a TFT display. The challenge I'm facing is that the convention heater options for displays are very expensive for my application (large volume). An ITO heater adds significant cost to the standard display. > > Given that my end product will be housed in a watertight enclosure of a small volume, it will have some internal heating from micro-controllers and other heat generating components. We'd ideally like to be able to read the display as low as -40C. The TFT that I'm looking at as an automotive spec and is rated to -30C although the suppliers indicates that it might not be readable at that temp. We typically update the display content around once per second. > > I'm reaching out to see if others might have some clever workarounds or suggestions for this challenge. > > I've often thought about placing power resistors strategically, or using FETs to generate and control heat, but had anyone out there had any success with this? Here is an old example I found from Electronic Design magazine http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf > > My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. > > Thanks! > > Paul
How much power do you think you'll need? I've used FET's for heaters down to 77K (LN2 tempseratures).. constant voltage and control the current. Maybe just some more insulation and the internal heat will be enough? George H.
On Wed, 16 Dec 2015 11:35:09 -0800 (PST), EnigmaPaul
<EnigmaPaul@gmail.com> wrote:

>Hi Folks - > >I have an application for low temperature readability of a TFT display. The challenge I'm facing is that the convention heater options for displays are very expensive for my application (large volume). An ITO heater adds significant cost to the standard display. > >Given that my end product will be housed in a watertight enclosure of a small volume, it will have some internal heating from micro-controllers and other heat generating components. We'd ideally like to be able to read the display as low as -40C. The TFT that I'm looking at as an automotive spec and is rated to -30C although the suppliers indicates that it might not be readable at that temp. We typically update the display content around once per second. > >I'm reaching out to see if others might have some clever workarounds or suggestions for this challenge. > >I've often thought about placing power resistors strategically, or using FETs to generate and control heat, but had anyone out there had any success with this? Here is an old example I found from Electronic Design magazine http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf > >My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. > >Thanks! > >Paul
That circuit is horrible, as most ED circuits are. You can use mosfets and/or resistors as heaters. A simple thermistor circuit could ramp up the heater as it gets colder; you don't need sophisticated, or even stable, control. People make stick-on resistive heaters, too. They aren't super cheap, but would be elegant packaging; just stick one to the back of the LCD. https://dl.dropboxusercontent.com/u/53724080/Thermal/Brick/Brick2.JPG If power is not a problem, you might prefer to heat the entire box, not just the LCD. A mosfet on a hest sink could do that. Some LCDs have a bias adjustment that can be used to improve their temperature performance. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
"EnigmaPaul"  wrote in message 
news:ce7fcc37-8743-41d1-a931-87368d9055a9@googlegroups.com...

Hi Folks -

I have an application for low temperature readability of a TFT display.  The 
challenge I'm facing is that the convention heater options for displays are 
very expensive for my application (large volume).  An ITO heater adds 
significant cost to the standard display.

Given that my end product will be housed in a watertight enclosure of a 
small volume, it will have some internal heating from micro-controllers and 
other heat generating components.   We'd ideally like to be able to read the 
display as low as -40C.  The TFT that I'm looking at as an automotive spec 
and is rated to -30C although the suppliers indicates that it might not be 
readable at that temp.  We typically update the display content around once 
per second.

I'm reaching out to see if others might have some clever workarounds or 
suggestions for this challenge.

I've often thought about placing power resistors strategically, or using 
FETs to generate and control heat, but had anyone out there had any success 
with this?  Here is an old example I found from Electronic Design magazine 
http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf

My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs.

Thanks!

Paul
==================================================================================

If it is that cold, is the uniformity of your heater going to be an issue? 
Don't want cold spots all faded out with nice bright colors an inch away 
:-).  How about a snowmobile/motorcycle grip heater on the back of the 
display?  Here's one example, where a guy used them to make his outside 
mirrors heated: 
https://www.tacomaworld.com/threads/el-cheapo-heated-mirrors.15958/.

-----
Regards,
Carl Ijames


On Wednesday, December 16, 2015 at 5:25:46 PM UTC-4, Carl Ijames wrote:
> "EnigmaPaul" wrote in message > news:ce7fcc37-8743-41d1-a931-87368d9055a9@googlegroups.com... > > Hi Folks - > > I have an application for low temperature readability of a TFT display. The > challenge I'm facing is that the convention heater options for displays are > very expensive for my application (large volume). An ITO heater adds > significant cost to the standard display. > > Given that my end product will be housed in a watertight enclosure of a > small volume, it will have some internal heating from micro-controllers and > other heat generating components. We'd ideally like to be able to read the > display as low as -40C. The TFT that I'm looking at as an automotive spec > and is rated to -30C although the suppliers indicates that it might not be > readable at that temp. We typically update the display content around once > per second. > > I'm reaching out to see if others might have some clever workarounds or > suggestions for this challenge. > > I've often thought about placing power resistors strategically, or using > FETs to generate and control heat, but had anyone out there had any success > with this? Here is an old example I found from Electronic Design magazine > http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf > > My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. > > Thanks! > > Paul > ================================================================================== > > If it is that cold, is the uniformity of your heater going to be an issue? > Don't want cold spots all faded out with nice bright colors an inch away > :-). How about a snowmobile/motorcycle grip heater on the back of the > display? Here's one example, where a guy used them to make his outside > mirrors heated: > https://www.tacomaworld.com/threads/el-cheapo-heated-mirrors.15958/. > > ----- > Regards, > Carl Ijames
Yes Carl, that certainly might be an issue. Although the display we are contemplating has an aluminum back so perhaps that might help distribute the heat across the back surface. We'd have to try it!
On Wed, 16 Dec 2015 16:24:38 -0500, "Carl Ijames"
<carl.ijamesXyZZy@ZZxyz.verizon.net> wrote:

>"EnigmaPaul" wrote in message >news:ce7fcc37-8743-41d1-a931-87368d9055a9@googlegroups.com... > >Hi Folks - > >I have an application for low temperature readability of a TFT display. The >challenge I'm facing is that the convention heater options for displays are >very expensive for my application (large volume). An ITO heater adds >significant cost to the standard display. > >Given that my end product will be housed in a watertight enclosure of a >small volume, it will have some internal heating from micro-controllers and >other heat generating components. We'd ideally like to be able to read the >display as low as -40C. The TFT that I'm looking at as an automotive spec >and is rated to -30C although the suppliers indicates that it might not be >readable at that temp. We typically update the display content around once >per second. > >I'm reaching out to see if others might have some clever workarounds or >suggestions for this challenge. > >I've often thought about placing power resistors strategically, or using >FETs to generate and control heat, but had anyone out there had any success >with this? Here is an old example I found from Electronic Design magazine >http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf > >My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. > >Thanks! > >Paul >================================================================================== > >If it is that cold, is the uniformity of your heater going to be an issue? >Don't want cold spots all faded out with nice bright colors an inch away >:-). How about a snowmobile/motorcycle grip heater on the back of the >display? Here's one example, where a guy used them to make his outside >mirrors heated: >https://www.tacomaworld.com/threads/el-cheapo-heated-mirrors.15958/. > >----- >Regards, >Carl Ijames >
That's pretty good, two heaters for $24, and a free toggle switch. http://www.amazon.com/Kimpex-Handlebar-Grip-Heater-12-170/dp/B002OP5YDM or this one http://www.amazon.com/HYspeed-Grip-Heater-Kit/dp/B00K359SOG/ref=pd_sim_263_5?ie=UTF8&dpID=514mL7XRvpL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=16QF0D88M6C6D5ZAZEYH -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Wed, 16 Dec 2015 13:52:09 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Wed, 16 Dec 2015 16:24:38 -0500, "Carl Ijames" ><carl.ijamesXyZZy@ZZxyz.verizon.net> wrote: > >>"EnigmaPaul" wrote in message >>news:ce7fcc37-8743-41d1-a931-87368d9055a9@googlegroups.com... >> >>Hi Folks - >> >>I have an application for low temperature readability of a TFT display. The >>challenge I'm facing is that the convention heater options for displays are >>very expensive for my application (large volume). An ITO heater adds >>significant cost to the standard display. >> >>Given that my end product will be housed in a watertight enclosure of a >>small volume, it will have some internal heating from micro-controllers and >>other heat generating components. We'd ideally like to be able to read the >>display as low as -40C. The TFT that I'm looking at as an automotive spec >>and is rated to -30C although the suppliers indicates that it might not be >>readable at that temp. We typically update the display content around once >>per second. >> >>I'm reaching out to see if others might have some clever workarounds or >>suggestions for this challenge. >> >>I've often thought about placing power resistors strategically, or using >>FETs to generate and control heat, but had anyone out there had any success >>with this? Here is an old example I found from Electronic Design magazine >>http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf >> >>My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. >> >>Thanks! >> >>Paul >>================================================================================== >> >>If it is that cold, is the uniformity of your heater going to be an issue? >>Don't want cold spots all faded out with nice bright colors an inch away >>:-). How about a snowmobile/motorcycle grip heater on the back of the >>display? Here's one example, where a guy used them to make his outside >>mirrors heated: >>https://www.tacomaworld.com/threads/el-cheapo-heated-mirrors.15958/. >> >>----- >>Regards, >>Carl Ijames >> > >That's pretty good, two heaters for $24, and a free toggle switch. > >http://www.amazon.com/Kimpex-Handlebar-Grip-Heater-12-170/dp/B002OP5YDM > >or this one > >http://www.amazon.com/HYspeed-Grip-Heater-Kit/dp/B00K359SOG/ref=pd_sim_263_5?ie=UTF8&dpID=514mL7XRvpL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=16QF0D88M6C6D5ZAZEYH
Even cheaper: http://www.amazon.com/TOOGOO-Motorcycle-Motorbike-Heated-Heater/dp/B00KBQCKVA/ref=sr_1_8?s=automotive&ie=UTF8&qid=1450303082&sr=1-8&keywords=grip+heater+kit http://www.amazon.com/EFORCAR-Motorcycle-Motorbike-Heated-Heater/dp/B00PJYYJ72/ref=sr_1_5?s=automotive&ie=UTF8&qid=1450303082&sr=1-5&keywords=grip+heater+kit -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Thanks for posting those, John.  Normally I love to chase down stuff like 
that, but I just didn't have the time and I had saved the link I posted (got 
it from another blog) and that was the fastest way to post the info and a 
link to a picture :-).

-----
Regards,
Carl Ijames

"John Larkin"  wrote in message 
news:7ln37b9v18pg903aimfmlqnukt0vhsat3b@4ax.com...

On Wed, 16 Dec 2015 13:52:09 -0800, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

>On Wed, 16 Dec 2015 16:24:38 -0500, "Carl Ijames" ><carl.ijamesXyZZy@ZZxyz.verizon.net> wrote: > >>"EnigmaPaul" wrote in message >>news:ce7fcc37-8743-41d1-a931-87368d9055a9@googlegroups.com... >> >>Hi Folks - >> >>I have an application for low temperature readability of a TFT display. >>The >>challenge I'm facing is that the convention heater options for displays >>are >>very expensive for my application (large volume). An ITO heater adds >>significant cost to the standard display. >> >>Given that my end product will be housed in a watertight enclosure of a >>small volume, it will have some internal heating from micro-controllers >>and >>other heat generating components. We'd ideally like to be able to read >>the >>display as low as -40C. The TFT that I'm looking at as an automotive spec >>and is rated to -30C although the suppliers indicates that it might not be >>readable at that temp. We typically update the display content around >>once >>per second. >> >>I'm reaching out to see if others might have some clever workarounds or >>suggestions for this challenge. >> >>I've often thought about placing power resistors strategically, or using >>FETs to generate and control heat, but had anyone out there had any >>success >>with this? Here is an old example I found from Electronic Design magazine >>http://www.tridatacom.co.uk/Downloads/Papers/DesignIdeas/ElecDes_Sep01.pdf >> >>My display is 4.3" color TFT with a 700 nit backlight from 10 white LEDs. >> >>Thanks! >> >>Paul >>================================================================================== >> >>If it is that cold, is the uniformity of your heater going to be an issue? >>Don't want cold spots all faded out with nice bright colors an inch away >>:-). How about a snowmobile/motorcycle grip heater on the back of the >>display? Here's one example, where a guy used them to make his outside >>mirrors heated: >>https://www.tacomaworld.com/threads/el-cheapo-heated-mirrors.15958/. >> >>----- >>Regards, >>Carl Ijames >> > >That's pretty good, two heaters for $24, and a free toggle switch. > >http://www.amazon.com/Kimpex-Handlebar-Grip-Heater-12-170/dp/B002OP5YDM > >or this one > >http://www.amazon.com/HYspeed-Grip-Heater-Kit/dp/B00K359SOG/ref=pd_sim_263_5?ie=UTF8&dpID=514mL7XRvpL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=16QF0D88M6C6D5ZAZEYH
Even cheaper: http://www.amazon.com/TOOGOO-Motorcycle-Motorbike-Heated-Heater/dp/B00KBQCKVA/ref=sr_1_8?s=automotive&ie=UTF8&qid=1450303082&sr=1-8&keywords=grip+heater+kit http://www.amazon.com/EFORCAR-Motorcycle-Motorbike-Heated-Heater/dp/B00PJYYJ72/ref=sr_1_5?s=automotive&ie=UTF8&qid=1450303082&sr=1-5&keywords=grip+heater+kit -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
On Wednesday, December 16, 2015 at 11:35:20 AM UTC-8, EnigmaPaul wrote:
 
> I have an application for low temperature readability of a TFT display. The challenge I'm facing is that the convention heater options for displays are very expensive for my application (large volume). An ITO heater adds significant cost to the standard display.
There are graphite sheet heat spreaders in many mobile phones, that heatsink the CPU to the back of the LCD display (pyrolytic graphite is very good at preventing hotspots). If power is at a premium, it (maybe) would make sense to pump heat from any powered chips into the display using thermoelectric 'coolers' (heat pumps, actually). A friend who did field work once told me that the only electronic devices in his toolkit that worked in the cold, were painted olive-drab or had 'Fluke' labels. He was talking 'cold' about 0 C.