is anyone familiar with the QT102 touch sensor?

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M

moinmoin

New Member
hi
i urgently need help with a circuit for a qt102 touch sensor (quantum research group). the problem i'm having is that i need to drive led's from it and it makes them very low in brightness when i use the same battery source than for the touch switch ... i think i need to drive it from a separate battery source and need help with a circuit design... mosfet maybe?
i am not so familiar with electronics but have come quite far with this project and do not want to give up now.
the battery source is 3.6V
here is a link to the datasheet of the QT102 : **broken link removed**
right this is it ...hope to hear from someone soon.
thanks
regards m
 

The data sheet states the max load is 2ma, if your led draws more than this you need to use one of the circuits shown on the data sheet to drive your led. The chip will drive the transistor and the transistor will take the load. I would think that the chip would drive an input of a pic ok, if you are using one, then you could drive your load from the pic or use a transistor to drive your load. Your answer is on the data sheet.
Do you have a circuit you are using, could you post it?
Good Luck
 
Last edited:
In addition to a transistor stage to drive the Leds, you may benefit from isolating the QT from sharp supply anomalies by using a small choke and some decoupling caps on the supply line to it.

rgds
 
thank you for replying so promply!
the led's i'm using run on 80mA directly from the battery.i am using four of these led's. If needed i can use a 3v button cell to drive the touch circuit which is the simplest one from the qt102 manuel figure 1.1 Sense Connection. could someone tell me which other circuit i have to use to run the led's separately from the switches power supply. i need quite ac detailed description as i'm not yet so fluent with my electronics.
thanks a lot for further help.....

m
 

You would use Figure 3.4 from the data sheet **broken link removed**
You should use one power source for the Touch Circuit and one for the Led's with a common negative line.
 
just having a closer look at the circuit and i realise that i'm not familiar with some terms. also i do not know which digital transistor to use.
if i use a 3.6v battery pack for the external led's and a 3v button cell for the touch switch what resistors do i need to make it work... and what is the load?
thank you for advise
m
 
help! please!!!

hi
anyone out there who knows? i'm really desperate to get this working as i need this to work for a product design prototype presentation on friday.
i'm sorry for my lack of knowledge in electronics, i'm just starting.
thank you for any advise!
regards
m
 
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