Heat Sensing Keypad

william chan

I recently saw some 3x4 numeric keypad where you actually touch the labeled plastic casing itself.
It seems that there are heat sensors behind the enclosure that can sense your fingertips' touch.
Anybody seen this before?

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www.fd.com.my
www.mercedes.com.my

Beau Schwabe

william,

can you provide a link? Are you sure it wasn't just a sensitive membrane keypad or capacitive keypad?

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

mctrivia

blackberry storm uses a heat sensitive system for detecting touch.

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24 bit LCD Breakout Board coming soon. $21.99 has backlight driver and touch sensitive decoder.

BradC

mctrivia said...
blackberry storm uses a heat sensitive system for detecting touch.

Got a reference for that? My data says it's a capacitive screen. Personally I've *never* seen a "heat sensitive" touch screen on any small device.

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If you always do what you always did, you always get what you always got.

mctrivia

I may be wrong. I was told it was and it does not respond like any cap sensitive screen I have used.

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24 bit LCD Breakout Board coming soon. $21.99 has backlight driver and touch sensitive decoder.

Erik Friesen

Get one of the quantum touch chips. They can be programmed in a number of ways and depending on the chip you can make sliders, etc. It will require making your own circuit boards though, and being a bit careful with the layout. I have used the qt60168 successfully with the propeller. On an outdoor project I am working on right now I am sensing touch with good levels of margin through 0.200" of plastic, using the qt60160. A 3x4 matrix is really not that difficult to implement if you follow their guidelines.

IRobot2

I have a blackberry storm too and I got curious as to how the touch screen worked. I had quite a bit of problems with mine when I first started using it but come to find out it was because I used a screen protector that it did not like. Once I used one that was designed specifically for the storm it worked fine. So my guess is that it is either capacitive or some type of SAW technology. I learned that from a BB web site.

Yet after doing a little googleing' I found a page that told about all the different types of touch screens on mobile phones (including IR which is what I think meant by the "heat sensitive" comment). It has the pros and cons of the three major types (resistive, capacitive, and IR) and is interesting even if your not referencing phones. Take a look if your interested.

http://www.phonearena.com/htmls/Article-Touchscreen-technologies-in-phones-article-a_3067-p_2.html

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Alex Burke
"Beware of computer programmers that carry screwdrivers." -Leonard Brandwein

william chan

Erik,

What is the difference between qt60168 and qt60160?
Which one is easier to use?

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www.fd.com.my
www.mercedes.com.my

Erik Friesen

The 60168 is an spi interface. The 60160 is i2c, or shift register output. Both use similar setup, but typically work out of the box. My propeller code is for the spi. I could pm you my code if you decide to try it. The 60168 is in a package with legs, and the 60160 is only in a small package without legs, that about requires a stencil of some sort to be able to solder it.

Amazingly enough, Mouser has them in stock here www.mouser.com/Search/Refine.aspx?Keyword=qt60168

Erik Friesen

So far, my luck has been good and every pcb I have built for these chips has worked. As far as ease of use they are very similar once you get the bit level interface together. The i2c version works a little better when you are using it with a micro that uses interrupts as it has a key changed output that goes high. With the prop code I just set it to poll the keys often and report to the higher level key array.

william chan

Erik,

I checked with Farnell and it seems the QT60160 is much cheaper. Why is that?
Can I solder it by hand?

Can I borrow your propeller code for the 60160?
How do you make the printed keypad words/numbers last without fading or peeling off?

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www.fd.com.my
www.mercedes.com.my

Erik Friesen

The qt60160 is a much smaller chip and for some reason they are pushing it instead of the 168. It will take a hot air gun at minimum to solder the qt60160. These are a bit tricky, even with a stencil. I just don't see doing it with a soldering gun.

My 60160 code is written in C for microchip products, so that won't be a good option.