Guide QT110 Touch-Sensitive Button Guide

Anyone who wants to purchase QT chips can go to www.saelig.com

Im not sure how many they have left but I just ordered 6 of them.

 

Farnell.com sells them. i bought SOIC (SMD) version of the QT110A there... Some QT chips (like 110) are discontinued, though...

 

I just got my QT113's from Saelig.com today. So, now I can finally finish up the final circuit and plug it all in.

I have had no troubles with my lights after this time yet. It seems once in a while the QT113 resets itself and the case lights will turn on and off a few times then goes back to normal working order.

 

Well it seems I am having problems. All my circuits are working fine except the one for my lights.

It all works fine at first then it will stop detecting my finger at all will turn on and off randomly. I wiggle some wires around and then lights flicker. It seems I am getting interference from something and its causing issues.

mvagusta or cpemma, have you got any ideas for this? It doesnt make any sense to me. All my connections are solild and nothing is shorting out.

Seems like interference or maybe something is being overloaded?

It was working great for over a week. Then it messed up and I replace the transistor and it worked a few times then quit. I dont know what to do.

 

I left the circuit unplugged for a day and today plugged it in and it worked again to turn the lights on an off, but moving around some wires would make the lights go to half brightness and not switchable.

Also after a few minutes of being on the transistor was extremely hot. So this makes me think it is the transistor that is the problem and it cant handle the load.

I looked at found the TIP142 transistor. Here is the datasheet http://www.datasheetcatalog.org/datasheet/stmicroelectronics/4132.pdf
Think this would solve the problem or is there something else wrong?

 

So have you checked with a multimeter to make sure that the invertors only use .5a?
If so, then using a small heatsink like a chipset heatsink, instead of insulating the transistor with glue, will be enough to keep it cool. The glue does not let the metal give off practically any heat at all! Bolting the transistor down and not gluing any part, not even the legs will let the heat dissipate nicely.

If your power usage is actually larger than .5a, then a higher power transistor may also be neccessary. I wouldn't be getting a covering a high power transistor in hot glue either btw, for the same reasons, but i doubt you actually need a beefier transistor anyway.

 

the inverter are supposed to only use 400mA.

also I dont have it covered in glue even. a previous one I did and now there is a spot for it to sit in without being covered in glue.

I guess maybe its not the transistor then?

It's got to be something to do with why when i move some of the wires around that the lights flicker and such. something is just not right.

Edit: It seems to maybe be something with my ground on the qt113. I'll have to wire up a new chip tomorrow and see if it works then I guess.

In the meantime, please help with the problem below......



Another problem. I am having issues with my touch switches used for ejecting my dvd drive. I have my chip wired up correctly. When i touch the electrode its output is shorted to ground like it should be. But for some retarded reason when I hook up the output and gnd of the chip to that of the dvd drive it doesnt work. I use voltmeter to check and on the output line it is now showing 0.14V!! WTH!? I even hooked up my reset switch to it which works perfectly and it does same.

I dont know what to do with this anymore..

 

You sure you are connecting the correct side of the dvd eject switch to ground?

Well if the transistor is getting hot, it needs a heatsink. Maybe there is more than .4a flowing and maybe you do need a bigger transistor aswell?

There's alot of connections here, take your time and double check everything with a multimeter and carefully compare each connection to your wiring diagram.

 

For the DVD drive, yes everything is connected exactly how it should. When I test with a voltmeter without the switch connected to the drive I get 3.26V at the positive wire. I tested the positive pin on the motherboard for the reset switch and it also shows 3.26V. So that part is the exact same. I tested the output of the QT113 when its not connected to the dvd drive and it outputs 5V normally then when touched it 0V (GND). My QT113 for my reset switch does the exact same. So far this is all the exact same and exactly how it should be. Correct?

But for some odd reason when I hook up the qt113 output to the positive if the dvd drive and the gnd of the qt113 to the gnd of the dvd drive it does not work and instead of getting the reading of 0V like I should I am getting a reading of 0.14V.

So what could cause this? Ive checked everything I can think of.

I'ma gonna redo the the qt113 for the lights and maybe I can get it all working fine. Im guessing after moving it around alot some of the wires came loose and thats what caused problems. It was working fine for over a week.


For the dvd eject if no solution is found i'll use a relay.

Thanks for helping.

 

I wouldn't mind seeing a circuit diagram of how you have hooked up the qt113 to the dvd drive, that way i know what is going on. The other thing, which might help you figure out for yourself what is happening, is that if you manually short the correct side of the dvd eject switch with a wire to earth, does the dvd eject?

I like your avatar btw I've been away for a couple of days and Rick Astley has been getting Relixed all over Bit

 

Here we go



I've done it the exact same as the way I've done the Reset switch. Thats what really makes it weird. And every single voltage reading is the same between the two except when the output is connect to the output pin on the dvd drive.


Yes I tried just touching the two wires together and it ejects. One of the first things I tried.

 

That looks good, but maybe you need to hook up a transistor to the output of the qt113, so that when the qt113 is triggered and goes low, the transistor is then triggered and shorts the dvd switch to gnd. I'm guessing that maybe the normaly high output of the qt113, might be upsetting the dvd circuitry?
Now i think we have to use a PNP transistor here... i haven't used one a PNP for ages though so i've sort of forgotten Maybe someone will chime in that knows the answer?

 

but when i touch the electrode the qt113 outputs GND (0V). When I check continuity with meter its not getting 100% which is what seems to be the problem.

I have a PNP transisitor (but its not rated correctly) and the continuity isn't 100% either so that wouldnt work.

Anyways with a NPN transistor itd be the opposite so it woudl always be connect the two untill I touch the electrode. Tried that and it dont work so PNP wouldnt work either.

I think I'll try the relay.

Here is the relay. http://www.allelectronics.com/make-a-store/item/RLY-506/5VDC-SUB-MINI-RELAY/1.html

Link to datasheet. http://documents.tycoelectronics.co...rchrtrv&DocNm=108-98005&DocType=SS&DocLang=EN

The relay is a D3009 on the datasheet. Seems to be what I need.

 

pfft relay, the output of the qt113 is 2oma max! I'd like to figure it out when i have some time... but i'm sure a few here know the answer... be patient, one of us will do it, eventually...

 

It's was a little quiet at work, and i went and got a little bit of exercise for my brain

I haven't built it, but i think it should work... i think Any small cheap pnp transistor like bc556 or bc558 etc should work fine, and i'm guessing with 1k for the resistor... a bit smaller or bigger shouldn't matter, i think... experiment and let me know! You probably have a few pnp transistors laying around!

 

I have one. Not sure if it works on the voltage of the QT113 though.


I will try to wire it up like that tomorrow. If it works then great. Otherwise I'll go with relay until I find solution.


Why "pffft relay"?? You saying it wouldnt work???

 

I'm just sick of relays, and thier annoying clicking and primitive unreliable mechanical weaknesses, I like doing things electronically when i can.

A relay should work fine, i didn't check the specs of that little relay, but even if that little relay only did need 20ma to work, that would be maxing out the capability of the qt113! which I expect would shorten it's lifespan... how long that means i have no idea? Maybe one week, maybe one year?

I think the pnp would only need over .7 volt to turn on, so it should work fine, i think

 

Heres the PNP transistor I have. I've only got one so if it works I will buy another.

http://www.onsemi.com/pub_link/Collateral/MPSA70-D.PDF


In the datasheet for the relay its rated for 2A. Not sure what you mean about maxing out the QT113?


Anyways Ima gonna try out the PNP now.

 

strange things are happenin!!!!!!!!!!!!

Ok so I hooked it up as you said with resistor and all.

I touch it and nothing. So I use volt meter. Put on end on gnd of course then the other on the output of the qt113 to see what its doing. Touch the electrode and the output goes to 0V exactly like it should. BUT, nothign happens. I take the positive end of the volt meter off the output and then, out comes the dvd tray. LOL Put the positive line of volt meter on output wire of qt113, tap the electrode, take positive line off output and the tray goes back in.


So... its ALMOST working. Any ideaers? Its driving me crazy!

 

sorry, i got close.... i thought i had figured it out I'm sure there's a few here that can sort this out, such as cpemma or cinnader for example...