LCD (TFT) Heater for low temperatures

Hi Folks -

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

Given that my end product will be housed in a watertight enclosure of a sma ll volume, it will have some internal heating from micro-controllers and ot her 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 sug gestions for this challenge.

I've often thought about placing power resistors strategically, or using FE Ts to generate and control heat, but had anyone out there had any success w ith this? Here is an old example I found from Electronic Design magazine h ttp://

formatting link

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

Thanks!

Paul

Reply to
EnigmaPaul
Loading thread data ...

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.

mall volume, it will have some internal heating from micro-controllers and other heat generating components. We'd ideally like to be able to read th e display as low as -40C. The TFT that I'm looking at as an automotive spe c and is rated to -30C although the suppliers indicates that it might not b e readable at that temp. We typically update the display content around on ce per second.

uggestions for this challenge.

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

formatting link

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.

Reply to
George Herold

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.

formatting link

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  
 Click to see the full signature
Reply to
John Larkin

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

formatting link

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:

formatting link

----- Regards, Carl Ijames

Reply to
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!

Reply to
EnigmaPaul

That's pretty good, two heaters for $24, and a free toggle switch.

formatting link

or this one

formatting link

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

Even cheaper:

formatting link

formatting link

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  
 Click to see the full signature
Reply to
John Larkin

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

Even cheaper:

formatting link

formatting link

--
John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement 
 Click to see the full signature
Reply to
Carl Ijames

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 heatsin k the CPU to the back of the LCD display (pyrolytic graphite is very good at preventi ng 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 pum ps, actually).

A friend who did field work once told me that the only electronic devices i n his toolkit that worked in the cold, were painted olive-drab or had 'Fluke' lab els. He was talking 'cold' about 0 C.

Reply to
whit3rd

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.