Guide QT110 Touch-Sensitive Button Guide

alright so wich one do i want?

 

is there a standy voltage line on an atx power supply that i could use for the power button on the computer?

 

dont laugh at me, thats what it looked like it said when i went to digikey ordering thing.

 

helloooo
which one do i get ?

 

mattthegamer463-

It's an IC that you use in combination with an electrode to make a sense-field button, basically. The electrode will create an electric field of a given strength through the material you place in front of it, like wood or plexiglas. When you touch that area the button is activated.

The entire circuit can be built for under $5 if you forego the LED and piezo speaker.

offroadracer789-

Yes. Please re-read the guide as I've specified exactly this information for you in post #5 and again in post #12.

Alternatively you could try using a WOL header off your motherboard, or perhaps the chassis-intrusion header (mine supplies only about 1.3V so it's insufficient to power the IC).

sdat1333-

Sorry for the delay. I'm in the middle of midterms in the first year of electrical engineering and it's a little intense right now. So while I'll do my best to answer your questions, a little bit of patience would be much appreciated.

To answer your question, I've used the active-low version of the QT110. I'm assuming you're not from North America if the Digikey part number in post #1 isn't helping you... perhaps you could try www.farnell.com or www.conrad.com for your location to find the chip. The spec sheet is also linked in post #1, I'm using the 8-DIP package.

If there are particular bits of the guide that aren't clear enough, please let me know and I'll try to rewrite, or maybe add more pictures.

 

sorry i didnt mean to come off sounding that way, tho i kno i did
im in the US so i can just order the same one u did
i just wanted to verify that touching the electrode would ground the output momentarily, which would do just the trick for my CD drive opening.

good luck on the midterms

 

No worries, I know what it's like to want to get started on a project.

Exactly, the QT110 grounds the output while activated, making it ideal for both your CD drive eject application as well as a PC's power button.

Thanks!

Basic Circuit Analysis on Monday, Ordinary Differential Equations on Thursday, and then C++ the week after that. Hurray!

 

this sounds like a pretty interesting thing to try. I'd like to do it but I'm rather new to things like this so I was wondering what I could use for an electrode and any tips for putting one behind a layer of acrylic to get it to work.

 

alright another thing
i dont want the piezo so can u link me to a capacitor on digikey i can use?
So I can just take the resistor out completely and use a capacitor right?

EDIT: oh another thing
dont USB ports get some of the 5vsb as well? So cant i just tie into my USB header instead?

EDIT AGAIN: Oh and i can leave the LED out completely right?

 

Yes some mobo's have 5vsb on their onboard USB headers, use a mulitmeter be carefull though!
The LED is not need, just for visual check.

 

so can someone give me a part number for a capacitor that will work for this
im still an electronics noob so bear with me

 

Really, anything metallic that you can solder the lead to will work.

In fact, when I was testing the button, I just taped the end of the electrode lead (without anything attached as an electrode, just about 1/4" of the wire stripped) behind the plastic front panel of my Antec Sonata, and upon touching that area, the PC would boot up. Touching it again, the PC would shut down.

From what I've read, some people have used metallic washers and others wire mesh as electrodes -- all readily available in a DIY store like Home Depot. So long as it conducts, it should do the trick.

 

Exactly right about the resistor -- just disregard it completely and replace the buzzer with a capacitor. QProx's only recommendations are that it be non-electrolytic (so a ceramic capacitor is fine, for example), and that it be between 10 and 30nF.

In fact, I've actually got a 10nF cap spec'd out in post #5, second paragraph under the photo, including the Digikey P/N. You may have skipped that.

If your mobo provides the power, by all means. Mine doesn't.

Of course, if you do hook into this line, you won't be able to connect a front-panel USB port to that header.

Yep, just disregard anything about connecting the LED to the circuit.

 

Another point of caution:

PLEASE don't just start connecting the circuit's power lead willy-nilly trying to find a power source. Use a multimeter while your PC is off (but the PSU is still on) to find a +5VSB line.

Exercise common sense, folks!

 

any ideas where this IC can be souced in the UK??

 

quick question. if ive got this hooked for my pcs on button and i hook it to the +5VSB line do i need to connect it to the spot where my normal case button connects? does it need to be connected to 5V power and connected to the motherboard power button connector, or just the mobo?

 

You have to hook them up to both.

The +5VSB line will power the chip, even when the PC is turned off. In post #4 this is the red wire annotated as "To Power".

The green wire in the same post that is annotated as "Output (To Motherboard)" goes to the motherboard's power button header.

To help folks understand this, let's make sure we understand how your PC turns on.

There's constant power going to your motherboard while the PC is off (assuming you having turned off the power supply or unplugged it from the wall!). The header on your motherboard has two posts: one is a ground, and the other is receiving power. The power button completes this circuit so that the current keeps flowing.

When you press your power button, this header is shorted to ground for a specified period of time. The motherboard detects this and uses it as a signal to power on the PC.

The QT110 circuit mimics this momentary power button.

As I stated at the end of post #25, try either farnell.com or conrad.com -- they will ship internationally, I'm told.

I don't have a part number available, but again what you want is the QT110 (active low, as opposed to the QT110-H, which is active-high), in the 8-DIP package (as opposed to surface-mount).

 

just need to clarify, (read the whole topic bout to goto bed )

Active Low = Ouput pin goes low when i touch the plate
Active High = Output pin goes high whine i touch the plate

which would make snece to me but i think i go muddled reading the topic!

thanks

 

You've got it!

 

lol, re reading it in a state of awakeness makes me realise what an obvious question/answere it was