I have also used the QT110 IC (for an inventive anniversary gift). (Sorry for the rather large size but I can't access my ftp site to resize it at the moment.) No values listed but you get the idea... Not perfectly operational, but I'm only a first year EE student .
What's the difference between the "Active Low" and "Active High" (the one with the "H" designation) models of these ICs?
Great question. Ative LOW and Active HIGH refers to the voltage level that the output signal changes to when triggered. Most signals on a motherboard are ACTIVE LOW. (CD-rom eject, Power, Reset, what ever) Active low means that the signal will react when "zero" volts (or ground) is applied to the signal. When reading signals on a IC chip, or schematic: Active LOW will be designated by a few things: /Signal Signal- or Signal with a ----- (bar) direclty over the text. Active high is the opposite. A signal pin that is active High stays at zero volts, and become triggered when pulled up to a higher voltage (Usualy +5volts) It is not used as often as it can be triggered by accident from a static shock. Active high will not have any special writing in a schematic. (Mabye a + signal if any) If you see a signal that has both + and - with the same labels. (Two pins, such as USB- USB+) Then that referes to a differental signal, and is a whole nother story. (Not used for triggering things, but data transfers)
Just curious if anyone knows the voltage output on this Qtouch IC? I want to be able to activate a relay when the sensor is touched, so I it would be useful to know the output value. I can't seem to find it in the datasheet. Thanks.
I considered using one of these for a cdrom eject. But i was concerend that the disk would eject when ever I reached for a cup of tea, or someone walked past the machine. Just something to bear in mind, positioning and sensitivity of the sensor will be very important.
Can you use these for a power-switch for a pc? I would LOVE to make the switch for my Sexy-G3 touch activated... (FYI - The switch in the G3 is a momentary ATX style soft-power.) What about distance/proximity? I'm assuming if I put it behind Plexi I would actually have to 'TOUCH' it to get it to power on, right? Would be fun to 'hide' the powerswitch so only You knew how to turn it on...
Over at farnell they sell these in QT110-IS & QT110-D flavours. can someone tell me the difference as the farnell spec sheets for both seem the same? will these work in the same manner as the suggested QT110H or QT110 models? I would buy from digi-key but f*** paying £20 for shipping and handling when the unit only costs a couple of quid.
The output is 5volts, BUT wait!, the current output is only 1mA It can sink up to 5mA. Read section 2.2.6 in the spec sheet: http://www.qprox.com/downloads/datasheets/qt110_102.pdf The sensativity is controled direcly by the size of the capacitor you use. I have found it ranges from touching the bare metal, up to a few feet. Yes, the active low output can be connected directly to the PWR header on your motherboard. (Sensativity is covered in the comment above) QT110-IS is probably a SSOP surface mount chip (Very small) QT110-D is probably the 8-pin DIP that most people will need. QT110H has an active high output (+5v out when active) QT110 has an active LOW output (0v when active) this is the most common type needed for things like DVD eject, reset, or power on a motherboard.
Holy crap, Zap. I only just posted that!! thanks for the reply, at least i know which to order - dont know which version (norm High/norm Low) farnell have so i'll have to see, if it's high i'll need to read the thread again to see what to do with the ic to reverse it's output to norm low. thanks again [edit] can't find any specs for the appropriate component to convert the high signal to low. Is it a transistor i need? if so what sort of rating. Infact, since my electronics knowledge is so crap maybe someone could just give a run down on what all the parts are used in coorz' schematic...
Thanks Zap, I will be ordering the QT110 and making a slick touch-button for my Sexy-G3. Is there a way to make the switch control an LED as well as close the circuit for the power switch. In other words, when touching the switch, and LED lights up (like on the Apple Cinema displays)?? EDIT: Answered my own question. The QT110 has a LED drive as well as a Piezo Drive for Visual and Audio feedback. Very very cool!
You should be able to purchase the chip in either active high, or active low. But to Invert the signal, you need an inverter. Or if you are controlling a relay, a NPN transistor is Active HIGH, and a PNP transistor is Active LOW Yes, the sensor can be a metal ring with an LED in the middle. But you need to put a tiny capacitor in parallel with the LED as the LED may cause the circuit to "stick" when you press it. They explain how to use LEDs in their 6-key product spec sheet.
Yes, but as the QT110 is available in either configuration, why not just by the one you need? (Hey i got 4000 posts, dang...i'm here too much)
Farnell only seem to stock the QT110H. The output can be easily inverted with a PNP transistor. Always use a resistor and transistor to drive a relay, never hook the output straight to the relay. -edit- the resistor + transistor will also take care of the 'heartbeat signal' which is superimposed on top of the output signal.
Coorz is right, farnell dont seem to do it, i will ask them to make doubly sure, but if i can only get the high version i'll have to invert it. as i said, not paying £20 p+p and handling for a £2 component @ digikey
Just so I'm clear, I need the ACTIVE HIGH version if I'm going to use it to activate a relay? Also, is it the ACTIVE HIGH or ACTIVE LOW version that outputs 5V?
Ah, cool. But for some reason, I feel more confused than before I guess I've just got to get the components and tinker. Thanks for the info!
