Post by thread:[PIC]: QT113H emulation

I EXTREMELY need help. I'm using the proximity sensor QT113H. It has an antenna who senses objects, hands, etc from up to 1 inch in distance and makes the output high as long as the object is in the range. The problem is I NEED want to emulate this behaviour wiht a pic 12F675. This is what I'm doing: The antenna is a piece of flat cable working as a capacitor, Here is the schematic: VCC GND + + | __ | +-o| |o-+ -o| |o-----------+---- ANTENNA -o| |o-+ ___ | -o|__|o-|---|___|-| | 470K VCC | + | | ___ | ___ +-|___|----+---|___|-+ 1K 1K | === GND created by Andy´s ASCII-Circuit v1.25.250804 http://www.tech-chat.de Basically I'm seting the GPIO2 to charge the ANTENNA 'capacitor' and after a short interval I use the AD0 to read the voltage over the ANTENNA 'capacitor' With no objects the voltage is higher then with na object. This is working great but with a short range, I need to increase it to up to 1 inch. I REALLY apreciate any help and I would pay for a solution. Regards, Octavio Nogueira Tato Equipamentos Eletrônicos Ltda (11) 5506-5335 ====================================================== spam_OUTnogueiraTakeThisOuTtato.ind.br ICQ# 222558485 BASIC Step - O microcontrolador mais fácil do mercado BASCOM - O mais poderoso compilador BASIC para ATMEL http://www.tato.ind.br ProPic tools - low cost PIC programmer and emulator http://www.propic2.com ======================================================

> The problem is I NEED want to emulate this behaviour wiht > a pic 12F675. Octavio, I've done something similar with CMOS logic, and I'm sure it would work with a PIC. I'll draw a schematic later today Basically, a 4011 oscillator drives a diode bridge at ~ 75kHz (frequency not too important). Across the other bridge terminals is a 1n0 cap, and from there to ground is a 47p cap. The aerial is also connected to this bridge. When an object like a hand or finger disturbs the aerial's field, the voltage across the 1n0 drops. A CA3140 op-amp amplifies and smooths this, followed by a Schmitt trigger to make a digital output. The output of the amp is easily measurable. I forget the gain off-hand, think it might have been about 20

--Message-Boundary-17019 Content-type: text/plain; charset=US-ASCII Content-transfer-encoding: 7BIT Content-description: Mail message body Something like this? Mark On 4 Feb 2006 at 1:49, Jinx wrote: {Quote hidden}> > The problem is I NEED want to emulate this behaviour wiht > > a pic 12F675. > > Octavio, I've done something similar with CMOS logic, and I'm > sure it would work with a PIC. I'll draw a schematic later today > > Basically, a 4011 oscillator drives a diode bridge at ~ 75kHz > (frequency not too important). Across the other bridge terminals > is a 1n0 cap, and from there to ground is a 47p cap. The aerial > is also connected to this bridge. When an object like a hand or > finger disturbs the aerial's field, the voltage across the 1n0 drops. > A CA3140 op-amp amplifies and smooths this, followed by a > Schmitt trigger to make a digital output. The output of the amp > is easily measurable. I forget the gain off-hand, think it might > have been about 20 > > > > --

You could also do a search for theremin. It's a musical instrument that uses fields. I know there are plenty of schematics available. <http://www.google.com/search?hl=en&lr=&q=theremin+schematic&btnG=Search> On 2/3/06, Octavio Nogueira <.....nogueiraKILLspam@spam@tato.ind.br> wrote: {Quote hidden}> > Well I have the 1MHz from PIC output available. > > Octavio Nogueira > Tato Equipamentos Eletrônicos Ltda > (11) 5506-5335 > ====================================================== > nogueiraKILLspamtato.ind.br ICQ# 222558485 > BASIC Step - O microcontrolador mais fácil do mercado > BASCOM - O mais poderoso compilador BASIC para ATMEL > http://www.tato.ind.br > ProPic tools - low cost PIC programmer and emulator > http://www.propic2.com > ====================================================== > > -----Mensagem original----- > De: .....piclist-bouncesKILLspam.....mit.edu [EraseMEpiclist-bouncesspam_OUTTakeThisOuTmit.edu] Em nome de > Jinx > Enviada em: sexta-feira, 3 de fevereiro de 2006 10:50 > Para: Microcontroller discussion list - Public. > Assunto: Re: [PIC]: QT113H emulation > > > > The problem is I NEED want to emulate this behaviour wiht > > a pic 12F675. > > Octavio, I've done something similar with CMOS logic, and I'm sure it > would work with a PIC. I'll draw a schematic later today > > Basically, a 4011 oscillator drives a diode bridge at ~ 75kHz (frequency > not too important). Across the other bridge terminals is a 1n0 cap, and > from there to ground is a 47p cap. The aerial is also connected to this > bridge. When an object like a hand or finger disturbs the aerial's > field, the voltage across the 1n0 drops. A CA3140 op-amp amplifies and > smooths this, followed by a Schmitt trigger to make a digital output. > The output of the amp is easily measurable. I forget the gain off-hand, > think it might have been about 20 > > > >