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'[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:
| __ |
-o| |o-----------+---- ANTENNA
-o| |o-+ ___ |
| ___ | ___
1K 1K |
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.
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> 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
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Something like this?
On 4 Feb 2006 at 1:49, Jinx wrote:
part 1 117 bytes content-type:text/plain; (decoded 7bit)
> Something like this?
> File: prox alarm.gif
Yup, same principle
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