Guide QT110 Touch-Sensitive Button Guide

until its sorted out can i go with that relay I posted? I've got other things I wanna order from that site as well so then I would order the relays at same time.

Thanks for trying.

This is some strange stuff.

 

Nah, the realy uses 28ma @ 5v, so it would be overloading the tiny maximum reccomended output current qt113. You'd have to use a transistor to trigger the relay, in the same way as the pnp diagram i just posted yesterday. Instead of connecting the Emitter of the transistor to the dvd button, you'd be connecting E to the relay coil, and the other side of the relay would go to 5v. The outputs of the relay would be used to connect the dvd button to ground. But stuff the relay, better to just get the pnp circuit working....

I don't know why my pnp circuit isn't working When you make voltage measurements with your multimeter, all the circuit sees is a high resistance from the probes... maybe try this:

Get a large resistor, like at least 100k, something big, and attach it from the qt113 output to ground. With that attached, i think the circuit should work, just like it did when you had your multimeter attached! [size=-10]i think [/size]

 

so do it the same as above but also have gnd attached to the base of the pnp with a 100k inbetween?

or maybe swap the 1K with a 100K??

see what happens is when i have the multimeter attached to read the voltages and i touch the electrode it only opens the drive AFTER i detach the multimeter.

I need to order my other stuff soon, so by weekend if I dont have it working i'll order the relays but will still try without.

Either way I'ma need some PNP transistors as i've only one.

Which on this page do it get? http://www.allelectronics.com//index.php?page=category&id=550200&p=1&template=

Sorry for troubling you so much. I've no clue about most of this stuff and its very confusing. Never learned anything about electronics in school.

 

Oh, seeing that the drive opens when you detach the multimeter... then i dunno... i'm gonna have to go back to the drawing board again!

I'd hold off before ordering pnp transistors until we get this pnp circuit figured out, i'm not sure about pnp transistors as i haven't played with them in ages, and seeing that my pnp dvd activation circuit isn't working properly, just hold on and one of us will figure this out. Hopefully guys like Cpemma and Cinnander see the problems we are having and give us a hand.

I want to see this get figured out too, i like learning stuff so it's all good

 

maybe you can direct them over here? I sent cpemma a PM same time as you but maybe you get can both of there attention.

 

That looks OK, 100mA rating and plenty of gain so it can take a fairly high value base resistor so not overload the QT IC. 2N3906 (200mA) are a useful general-purpose PNP, or the PN2905 at your link will take 600mA.

With PNP transistors the "high" signal at the base must be over [emitter voltage less 0.6V] for it to turn off, so you can't use, say, 5V from the QT to switch 12V across the transistor and load. You're measuring 3.26V between ground and 'E' which should be OK.

What's happening with the multimeter lead I don't know, sounds like something's over-sensitive or loose.

It does also sound like you just need a short pulse to the DVD switch to operate the tray, not a toggle action from the QT113.

 

I dont have the QT113 in toggle mode. It is in momentary mode. While at idle it output 5V. While electrode is being touched it goes to 0V/GND.

Not sure I understand what you are saying. How should I have this wired up for it to work then? I SHOULD be able to not use a transistor at all but that dont seem to work.

 

I just had an idea, i think i know why my pnp circuit wasn't working! Try this out, and let me know how it goes!

100k might be too big actually, maybe 10k or less would be better... try a couple out and see how you go, but don't go under 1k to keep the dvd safe.

 

You just taking guess here?

I will try it out. Thanks!

 

finally got around to trying that out. still no go.

like before, almost works. if I use the volt meter and have it connected to the qt113 output when i touch the electrode it opens tray. tried different resistor ratings and no go.when i check the voltages at the Emitter it only goes down to 0.7v. Im thinking for it to work its supposed to go to 0V. Correct?


I think im gonna give up on this, can you tell me how to wire up a circuit that uses a relay and transistor together (since the relay draws too much current)??

Unless you got another idea.

 

Damn.. i dunno why the pnp isn't shorting the dvd button to ground

If you just wanted to hook up a relay, you'd just have to use a circuit like this one:

But just connect to the relay coil instead of the invertor. and the relay output contacts short your dvd button to ground.

edit: actually... maybe just try hooking up the dvd button like this before you get the relay... so the dvd button goes to C, and you don't have to worry about the yellow 12v lead. Maybe i've just been using a pnp when i should have been just using an npn!

 

npn wouldnt work. its activated when it has voltage going to the base. The QT113 outputs 5v until being touched. then it outputs 0V. So PNP is what should be used. Or am I thinking of it wrong.

Anyways, I'll try it one last time. Thank you very much!


I still havent re-made my light switch circuit as it was messing up and flickering and I realized it was my solders coming loose. So I need to redo that and hope it works.

 

didnt work...... ((((((((

oh well. relays is how it will be then

 

Whoops, sorry, i got mixed up and forgot that the invertor circuit was npn since the qt113 was being used in toggle mode there

So for driving a relay, you wouldn't be using toggle mode, so we have the same problem! We'd need to get a pnp circuit working to drive the relay... now i think my previous circuit with the pnp & the 100k resistor should work perfectly, you'd just be leaving out the 100k and connecting the relay's coil there instead.

I really don't know why none of the circuits we have tried have not worked properly with the dvd I'll try it myself one day.

I guess one possibilty is that the pnp you tried using was faulty maybe?

 

not sure why they havent worked either. if i have the volt meter connect to the output of the qt113 then it works. LOL


maybe bad transistor. i'll be ordering more anyways so i could always try it again without relay with the new transistors.

 

UPDATE:

got the relays and stuff I ordered. I wired them up and I think this will work. Currently as soon as I plug in the circuit the drive opens up so thats telling me that I need to switch some wire or something.

The relay is an SPDT so I just need to put the dvd drive on the other pole i'm guessing.

I would have tried it already but I cant continue right now. But it seems like it will infact work!

 

I'd like to try this myself, but i have way too many things to do at home. I have a few projects of my own as well that are on hold

Don't forget that even without any pnp transistor or relay or whatever, just the low output from the qt113 should be enough to trigger the dvd tray open, so i've got a feeling there is some sort of wiring or connection error since none of the methods we've tried have worked.

 

we'll see. I only wired it up. Will test with meter to see where the problem is but I am sure it will work.



I hope!

 

Just in case, here's the relay version:

Notice that the earlier one was the npn version for a qt113 in toggle mode.

 

I tink a see what is wrong. I mixed up the collector and emitter.


nice coil