Resistive vs. Capacitive touch screen

[Wilson__]

1.  Can resistive touch screen (3 to 4 inches) work with finger (lower pressure) instead of stylus (higher pressure at a fine point)?

2.  Does resistive has shorter life?  May be the two layers will stick together (instead of bounce back out) and fail?

3. Any other short coming for resistive, other than restricted multipoint?  Seem they are still in advertisement for lower cost DIY/Arduino although cell phone are now exclusively capacitive??

Many thanks

[wraper]

1.  Can resistive touch screen (3 to 4 inches) work with finger (lower pressure) instead of stylus (higher pressure at a fine point)?

It can, not that well though.

2.  Does resistive has shorter life?  May be the two layers will stick together (instead of bounce back out) and fail?

Capacitive touch screens do not wear out basically. Resistive touch screens wear out easily, especially with no screen protector and when poked with unsuitable things which is not that rare.

[coppice]

1.  Can resistive touch screen (3 to 4 inches) work with finger (lower pressure) instead of stylus (higher pressure at a fine point)?

2.  Does resistive has shorter life?  May be the two layers will stick together (instead of bounce back out) and fail?

3. Any other short coming for resistive, other than restricted multipoint?  Seem they are still in advertisement for lower cost DIY/Arduino although cell phone are now exclusively capacitive??

Many thanks

Just before Apple launched the first iPhone the cost of a capacitive screen was really high. HTC was making a lot of smartphones with resistive touch screens that worked pretty well. They operated with fairly light finger touch, and were fairly robust. They would eventually scratch up, though, and they were never quite as light touch as a capacitive screen. Apple gambled on high volumes driving the price of capacitive screens through the floor, and stirred up their supplier base enough to succeed. Nobody wants a resistive touch screen after experiencing a good capacitive one, but the last of them were not that bad. There are still places where electrical noise makes capacitive screens quirky enough to keep resistive ones in play. There are also infra red beam matrix touch screens, used in noisy environments, and sensitive places like medical applications, where capacitive doesn't cut it. If your mucky fingers stop registering on your phone, you wipe the screen and your fingers. You don't want that kind of ambiguity with patient systems. I think my Volvo uses an infra red touch screen for noise reasons. Some cars certainly have done. Some e-book readers also use infra red.

[wraper]

Infrared touch was used for ages. I repaired elemental analyzers made in early-mid 90s with IR touch, EL screen and 386sx/486sx CPU, some of them are still working.

[Wilson__]

What resolution is infra?   May be 3 or 4 or 5 rows/column of emitters and receivers, making 9, 16 or 25 'KEYS'  on screen and it is a lot of 'keys' as compare with physical key on traditional hard-key devices.

[harerod]

From what I have seen, capacitive is far superior in haptics and optics.
However, resistive will accept input by a single gloved finger, no tool required. Combined with an appropriate user interface, this may be a valid solution for environments where you don't want to pull off your glove.
A simple civilian application would be a Garmin Montana.

[m k]

Not so long ago I scrapped some working Elo Touch monitors.
Connections were sooo out of date.

[wraper]

IR does not need actually touching the screen to work, so it may be a good solution for cases where high ruggedness is needed and it should work with gloves. However it has limitations such as low resolution, no multi touch and that it must be put in bezel above recessed screen.

[tooki]

1.  Can resistive touch screen (3 to 4 inches) work with finger (lower pressure) instead of stylus (higher pressure at a fine point)?

2.  Does resistive has shorter life?  May be the two layers will stick together (instead of bounce back out) and fail?

3. Any other short coming for resistive, other than restricted multipoint?  Seem they are still in advertisement for lower cost DIY/Arduino although cell phone are now exclusively capacitive??

Why would you think they would not work with a finger?!?

Resistive touch screens are still widely used, just not on phones and stuff. Resistive touch screens are cheaper (especially for large ones), but their main advantages are mechanical robustness, flexibility as far as what is used to push on them (bare fingers, thick gloves, or any hard object will work), and above all, indifference to contamination (assuming one seals the display). Capacitive touchscreens don’t work reliably when rained on, for example, and won’t respond to thick gloves or a pen.

These are reasons why things like ATMs, transit ticket machines, and industrial control displays are overwhelmingly resistive.

[wraper]

These are reasons why things like ATMs, transit ticket machines, and industrial control displays are overwhelmingly resistive.

I don't recall ever seeing ATM with a resistive touch screen. Industrial control yes, and I've seen holes worn out in them. I don't get the claim about mechanical robustness, they are not that robust at all. They still have a glass that can crack on an impact and they have plastic films on the outside that can be damaged and wear way easier than glass. Protective films greatly compromise sensitivity.  Resistive touch is advantageous in presence of water or other contamination, electrical interference and when used with gloves.

[dferyance]

I have been surprised at how well capacitive touch screens have improved. I remember when the iPhone came out I was disappointed it was capacitive. You have better precision with a resistive touch screen. It is all analog while capacitive touch is limited by the grid pattern and spacing. My thought was with having such a small screen, combine that with not being able to use a stylus and the lower precision would greatly limit it's capabilities. In a sense it has but it seems no one cares.

Capacitive touch has gotten really good at working in wet conditions, and higher precision. And resistive definitely wears out easier. There may still be cases for resistive but in general capacitive is usually the better route.

[coppice]

What resolution is infra?   May be 3 or 4 or 5 rows/column of emitters and receivers, making 9, 16 or 25 'KEYS'  on screen and it is a lot of 'keys' as compare with physical key on traditional hard-key devices.

Why would you expect infra red to limited like that? They offer similar resolution to capacitive screens.

[coppice]

I have been surprised at how well capacitive touch screens have improved. I remember when the iPhone came out I was disappointed it was capacitive. You have better precision with a resistive touch screen. It is all analog while capacitive touch is limited by the grid pattern and spacing. My thought was with having such a small screen, combine that with not being able to use a stylus and the lower precision would greatly limit it's capabilities. In a sense it has but it seems no one cares.

Capacitive touch has gotten really good at working in wet conditions, and higher precision. And resistive definitely wears out easier. There may still be cases for resistive but in general capacitive is usually the better route.

Even the first iPhone was not limited to the grid spacing. They have always used interpolation to achieve a pretty high resolution. The capacitive pads on notebooks were never low resolution. Why should one on a phone be? The problem with the phones, and the reason the cost was initially so high, was reliably making the very narrow ITO traces needed.

[coppice]

These are reasons why things like ATMs, transit ticket machines, and industrial control displays are overwhelmingly resistive.

I think you mean were resistive. The new designs aren't.

[Wilson__]

Many thanks.  I speciically referred to 'keys'.  That is, on screen 'soft key' instead of hard physical keys.  The number of key I stated is generally that a 'machine' need.  Bank ATM, weighting scale and may be some industrial control machine.  A few keys to select "one of out several" menu jump to next screen level.  Up/Down arrow to trim parameters, says temperature controller.

A few row is easily done with IR emitted and sensor.   Yes, you can have high resolution sensor.  Say, use an traditional (the original wide spread use version, 30 years ago, Rockwell modem inside. Not the advanced higher resolution G3 version that did not got wide deployment) fax machine 'contact' (direct touching document, no lens) linear 1-D CCD sensor is about 100 dot per inch if my memory is correct. 

[coppice]

Many thanks.  I speciically referred to 'keys'.  That is, on screen 'soft key' instead of hard physical keys.  The number of key I stated is generally that a 'machine' need.  Bank ATM, weighting scale and may be some industrial control machine.  A few keys to select "one of out several" menu jump to next screen level.  Up/Down arrow to trim parameters, says temperature controller.

There have been numerous types of touch screen offering only a small number of sensed areas. They have often used a coating on the surface of the glass, with contacts resistively bridged by a finger.

A few row is easily done with IR emitted and sensor.   Yes, you can have high resolution sensor.  Say, use an traditional (the original wide spread use version, 30 years ago, Rockwell modem inside. Not the advanced higher resolution G3 version that did not got wide deployment) fax machine 'contact' (direct touching document, no lens) linear 1-D CCD sensor is about 100 dot per inch if my memory is correct.

If you look at the infra-red touch sensors in cars and e-book readers they put something like those FAX machine strips behind the panel, with a light pipe that wraps over the edge of the panel. The part above the panel is very slim, so the border only has to be raised a small amount above the display panel itself.

[Wilson__]

Many thanks.  Just curious.  Traditional black-and-white LCD are metal traces on glass and quite high resolution by 1986, 640 x 200, IBM PC Convertible.  Not sure if it was ITO or other metal??

[coppice]

Many thanks.  Just curious.  Traditional black-and-white LCD are metal traces on glass and quite high resolution by 1986, 640 x 200, IBM PC Convertible.  Not sure if it was ITO or other metal??

Good question. I don't know. However, before the iPhone was launched HTC had one phone with a cap touch display in small volume, very unprofitable production. People in Taiwan we were talking to at the time, serving both Apple, HTC and others who were trying to jump on the bandwagon, were struggling with this problem.

[tooki]

I have been surprised at how well capacitive touch screens have improved. I remember when the iPhone came out I was disappointed it was capacitive. You have better precision with a resistive touch screen. It is all analog while capacitive touch is limited by the grid pattern and spacing. My thought was with having such a small screen, combine that with not being able to use a stylus and the lower precision would greatly limit it's capabilities. In a sense it has but it seems no one cares.

Capacitive touch has gotten really good at working in wet conditions, and higher precision. And resistive definitely wears out easier. There may still be cases for resistive but in general capacitive is usually the better route.

Maybe resistive is more precise in theory, but in practice they’re way worse. One big reason for this is that resistive touch screens must be carefully calibrated (remember doing that on Palm handhelds? ), while capacitive ones don’t need that since the grid is precisely placed at the factory.

[wraper]

Got to one of those IR touch devices I talked about, this one is 29 years old.

[everglory]

Yes, a 3–4 inch resistive touchscreen can normally be operated with a finger. It does not require a stylus.

However, it responds to physical pressure rather than just contact. A fingertip spreads the force over a larger area, so it may need a slightly firmer press than a stylus or fingernail. With reasonably large on-screen buttons, finger operation should be fine.

Resistive touchscreens do have a finite mechanical life because the upper film flexes every time it is pressed. The two conductive layers are kept apart by tiny spacer dots, so they should not simply stick together during normal use. On cheap or heavily used panels this can happen, but scratches, worn conductive coating, damaged edge seals, calibration drift and dead areas are more common failures.

Some other disadvantages compared with capacitive touch are:

* the flexible top film scratches more easily than glass
* slightly lower light transmission and contrast
* less pleasant swiping and dragging
* periodic calibration may be required, especially with 4-wire panels
* a thick protective cover glass cannot be placed over it because the surface must flex
* 4-wire panels can lose accuracy as frequently used areas wear

On the other hand, resistive touch still has some useful advantages. It works with gloves, a plastic stylus, a fingernail or almost any other object. It is inexpensive, accurate for small controls and easy to connect to a microcontroller, sometimes using only a few ADC pins.

That is why it is still common in Arduino projects and some industrial equipment. Mobile phones moved to capacitive touch because users expect a hard glass surface, very light touch and smooth multi-finger gestures. For a small, low-cost interface with simple buttons, resistive touch can still be a perfectly reasonable choice.