Tacᴛɪʟᴇ Sensors

[Electroenthusiast]

Had these questions from many days. Though the question may be silly sort of thing for some of you here, i couldn't find a suitable answers in the Google. Moreover, fellow members here recommended me to open a thread, so that we can have a discussion on it.

The question is about Tacᴛɪʟᴇ Sensors(ᴛouch Sensors)... These sensors are used in most etouch gadgets nowadays. I couldn't find an article that can give info abt Tacᴛɪʟᴇ Sensors, so any links about the topic will be appreciated.

I have some questions about these sensors:
Q1: Why(and How) are some(iPads/Laptop Touchpad) of these sensors sensitive only to to human hand/skin? How do they work so?
Q2: When i use both my hands to these sensors (simultaneously) then there is no change in the cursor movement? Why is this so?
Q4: Some sensors that i've seen, require change in contact(maybe both direct/indirect). Ex: If i keep touching the transducer(touch sensor), and another person touches me and releases his hand. This causes Touch Switches ON/OFF, even though i dont to the work(instead another person does it for me indirectly). This happens even dirctly: i mean, me touching and releasing my hand also makes the switch work.
Q5: Some of them wont work without the person touching(standing/ footrest on) the Ground. Why and How?

I want explanation for these/links where i can find some info abt these. Thanks in Advance.

 

[4pyros]

You need to google "touchscreens"
https://en.wikipedia.org/wiki/Touchscreen

 

[KeepItSimpleStupid]

In a nutshell, resistive, capacitive and I guess we could call it inductive.

A touch lamp dimmer operates very differently. Usually it detects the presence of AC from the 50/60 Hz power line that's ever present. Your body acts as an antenna.

Knobs and similar sensors can detect the change in capacitance when you touch them.

Touch screens can be resistive. There are resistors now which will change it's resistance depending on where you press. Resistive screens need to be calibrated.

Old technology that was used had a course X-Y matrix that was physically pressed made from a transparent oxide semiconductor like ZnO or ITO. There was also a technology that had IR detector and receiver pairs on the screen.

Here is a link to get started: https://en.wikipedia.org/wiki/Touchscreen

 

[Electroenthusiast]

You need to google "touchscreens"
https://en.wikipedia.org/wiki/Touchscreen

i thought tactile sensors = touch pads + touch screen and so on... but there was no article with that name there.... Thanks for the Info.

In a nutshell, resistive, capacitive and I guess we could call it inductive.

A touch lamp dimmer operates very differently. Usually it detects the presence of AC from the 50/60 Hz power line that's ever present. Your body acts as an antenna.

Knobs and similar sensors can detect the change in capacitance when you touch them.

Touch screens can be resistive. There are resistors now which will change it's resistance depending on where you press. Resistive screens need to be calibrated.

Old technology that was used had a course X-Y matrix that was physically pressed made from a transparent oxide semiconductor like ZnO or ITO. There was also a technology that had IR detector and receiver pairs on the screen.

Here is a link to get started: https://en.wikipedia.org/wiki/Touchscreen

Ya... thanks, the link is informational, but i have some questions from it.
That explains abt TouchScreens, similarly for touchpads(might be bit similar).

Some of them are sensitive only for Skin/Stylus/Digital Pen and with no other device, i have a bit hassle in learning it's working and why others wont work. Also please can you briefup how multi-touch can be detected from these technologies(i mean what changes are required).

Resistive: The panel then behaves as a pair of voltage dividers, one axis at a time. For a short time, the associated electronics (device controller) applies a voltage to the opposite sides of one layer, while the other layer senses the proportion (think percentage) of voltage at the contact point. That provides the horizontal [x] position. Then, the controller applies a voltage to the top and bottom edges of the other layer (the one that just sensed the amount of voltage); the first layer now senses height [y]. The controller rapidly alternates between these two modes. As well, it sends position data to the CPU in the device, where it's interpreted according to what the user is doing.

Voltage Divider: This means the output voltage depends on the position of the Hand(/Stylus), and that makes it possible to detect the position. Am i right.Is it the same way how Optical Mouse Work?

The link doesn't explain about Touch Detection in Light Dimmer(as in the case i earlier said - Direct/Indirect), and the Footrest on Ground condition that is required in some of the sensors.

 

[KeepItSimpleStupid]

OK, here is another link with links: https://en.wikipedia.org/wiki/Force-Sensing_Resistor

Here are some datasheets on some touch IC's used for lamps: https://www.lsicsi.com/lighting_controls.htm

and some IC's for sensing capacitance: **broken link removed**

and for the touchpad: https://en.wikipedia.org/wiki/Trackpad

Voltage Divider: This means the output voltage depends on the position of the Hand(/Stylus), and that makes it possible to detect the position.

Yep.

Am i right.Is it the same way how Optical Mouse Work?

Nope.

There are three sensing technologies that I'm familiar.

1) Two wheels sense direction and speed from a single ball.
2) A grid is placed as the mouse pad and the mouse reads the grid.
3) An accelerometer should also be able to detect movement. This is the same gizmo that's able to re-orient the screen on your cell phone.
https://www.uchobby.com/index.php/2007/10/27/accelerometer-based-mouse/

 

[KeepItSimpleStupid]

Q1: https://en.wikipedia.org/wiki/War_of_Currents
Q3: Explain more. Fire alarm? Warning system? Lunch bell? Remember the Flintstones?
Q4: Explain more

 

[Electroenthusiast]

Thanks KeepitSimpleStupid... i'll come back after going through the links.

@war of currents, ya i've read it... but it doesnt explain whether edison had a valid reason(really hazardous) for discrediting tesla's AC.
q3... i got the answer....

 

[alec_t]

Is it the same way how Optical Mouse Work?

No. An optical mouse essentially detects changes in successive optical images of the surface texture beneath it.

 

[KeepItSimpleStupid]

Q1: You will probbaly find that MOST people feel that DC is more hazardous because the current goes to zero and it "could" give you a chance to break away.

The heart stops when ABOUT 10 mA of current goes through the heart muscle.

Your new Q3:
The OS does not write every block to disk when changes are made. There is a RAM cache that needs to be written back when the drive is removed. The same is true for any hard or solid state drives. There should be some options to control this. A larger cache means better speed and greater risk of data loss.

 

[Electroenthusiast]

No. An optical mouse essentially detects changes in successive optical images of the surface texture beneath it.

What if i use a clear white/uniform mouse pad below it? Yes... they use that technology.
I have two optical mice here, one has a led at one end and it switches on only when there is any change in the texture. Earlier Version of optical mouse is bit complex. But, why do they want to use these complex image processing for this minor work. Moreover, mechanical mice did the same job.

Q1: You will probbaly find that MOST people feel that DC is more hazardous because the current goes to zero and it "could" give you a chance to break away.

The heart stops when ABOUT 10 mA of current goes through the heart muscle.

Yes, right... But Edison opposed, he was contradictory. He said AC is hazardous, but i think had no valid reason for it (except his personal enemity & business prospective).

Your new Q3:
The OS does not write every block to disk when changes are made. There is a RAM cache that needs to be written back when the drive is removed. The same is true for any hard or solid state drives. There should be some options to control this. A larger cache means better speed and greater risk of data loss.

The data will be copied to RAM(if i'm correct), Consider this example. When i was a kid, i used to remove the CDROM from the CD tray, while playing the game(jus used to feel that i can increase the life of the game CD by doing that). I was able to continue playing the game. I wanted to know whether this happens with the dvd players and other devices like them.

 

[KeepItSimpleStupid]

ROM's are a removable anytime device, meaning they can be removed at any time. No harm can be done to the CD/DVD. The elctronics won;t let the drive open when spinning UNLESS you eject with a paper clip. The game would be too slow to run from the CD. I'm sure at certain stages, the CD would be accessed. A tradeoff between the amount of RAM and/or disk space. The early games were nothing but a ROM memory chip with fast access.

Q5: One of the upgrades to the phone system involved SS7 or sgnaling System 7. https://en.wikipedia.org/wiki/Signaling_System_7 This put connection stuff out of band. Way back when the illegal "blue box" https://en.wikipedia.org/wiki/Blue_box could route your call to your neighbor using a satellite link if you wanted.
Tones were present at the beginning of long distance calls that routed those calls. Thus the signaling was "in band".

*69 will return the caller ID value which is not reliable.

Call trace will return the ANI or Automatic Number Identification which cannot be spoofed. Calls to 800 numbers will use ANI. Calls to large corporations may also use ANI. https://en.wikipedia.org/wiki/Automatic_number_identification

 

[Electroenthusiast]

ROM's are a removable anytime device, meaning they can be removed at any time.

Can i do the same thing with USB Memory sticks? They are also ROMs.

Way back when the illegal "blue box" https://en.wikipedia.org/wiki/Blue_box could route your call to your neighbor using a satellite link if you wanted.

This happens through Central Office, if i'm right.

Call trace will return the ANI or Automatic Number Identification which cannot be spoofed. Calls to 800 numbers will use ANI. Calls to large corporations may also use ANI. https://en.wikipedia.org/wiki/Automatic_number_identification

Isn't it possible to use a feature like #69(for 800 calls/ANI)?

Err:

You must spread some Reputation around before giving it to KeepItSimpleStupid again.

So i need to add reputation to someone to repute U.

 

[KeepItSimpleStupid]

USB Memory sticks are not ROM's. Now, if it was a say a 4GB SD card with the write protect tab on, then it would be OK.

You shouldn't have any problems pulling a USB memory stick if you only read from it, but I would never say you won't.

Call routing
Now the routing signals occurs out of band. Before the routing signals were passed in-band, meaning on the telephone pair that carried the voice.
In the simplest case the whistle from the Captain Crunch cereal boxes were tuned to 2600 Hz. That tone would disconnect billing, but not the call. Hence, you could call someone, use the whistle and continue talking forever without being charged. Now the CO would detect that you hung up and tell the billing system under another communications path, that it should stop billing for this call.

Here is a real world example of ANI/Caller ID
1) Doctor office main phone: 555-5000; Your Health Inc
2) Doctor's personal phone: 555-5026; Dr. Smith
3) Your home: 555-9999; Mr. X pt.

Dr. calls you from phone (2); Your caller ID says Your Health Inc. or phone (1).
Dr. Calls internally; so the caller ID reports the Dr's real phone or phone (2).
ANI will always report phone 1.

Dr. Calls 911 on personal phone (2); ANI reports the real number of (2) to the 911 Call center.