b.kainka
I used Basom to program the Tiny13. The source is so short I can show it here. I used an integration time of 10 µs. At the beginning I collect a reference value Ref to know the LED voltage without signal. This is used later to detect the voltage loss caused by an RF signal.
Bas and HEX files: http://www.elektronik-labor.de/AVR/Sparrow/SparrowRX.html
Cheepit upload via Sound: http://tiny.systems/categorie/cheepit/RFDetector.html
Video:
The project goes on. Leander made a simple transmitter: The ATtiny13 generates an RF signal around 300 kHz and is tuned to match the LC circuit. A second LC circuit receives the RF energy. He also built a simple data link using two coils with hardly any additional components on the Tiny13.
'ATtiny13 RF receiver
$regfile = "attiny13.dat"
$crystal = 1200000
$hwstack = 8
$swstack = 4
$framesize = 4
Config Portb = &B000000010
Dim T As Byte
Dim N As Byte
Dim D As Word
Dim Ref As Word
Dim Diff As Word
Config Adc = Single , Prescaler = Auto
Config Timer0 = Pwm , Prescale = 8 , Compare B Pwm = Clear Up
D = 0
For N = 1 To 20
Portb.3 = 1
Portb.3 = 0
Waitus 10'integration time
D = D + Getadc(3)'LED2 voltage
Next N
Ref = D / 20
Do
Portb.3 = 1
Portb.3 = 0
Waitus 10'integration time
D = Getadc(3)'LED2 voltage
If D >= Ref Then
Pwm0b = 0
Else
Diff = Ref - D
If Diff > 2 Then
Pwm0b = 128'sound and LED1
Waitms 50
End If
End If
Loop
End
Yann Guidon / YGDES
Rhea Rae
mircemk
jurc192
Your circuit reminds me of a capacitive touch sensor I built using a microcontroller and a single resistor to detect the presence or absence of a human finger near an antenna plate. I used an output pin to alternately drive the antenna high then low through the resistor each time the threshold voltage was crossed. On an input pin directly coupled to the antenna, the software measured how long it took to charge and discharge the capacitive load in order to determine if a finger was near the antenna. <p>
Here, you appear to be cleverly using a diode (LED) to rectify an AC e-field. Then with a microprocessor input pin, your software leverages the internal pull-up, FET, and gate capacitance as an oscillator, comparator, and integrator. <p>
My question is whether this is a detector of precisely modulated RF or is it simply an indiscriminate RF noise detector <i>a la</i> Marconi? In other words, can your technique being used to “tune in” to a specific modulation scheme (e.g, a sine wave frequency or DSSS), or can it only measure the <i>amplitude</i> of a broadband AC/RF field that is capacitively coupled to your antenna? Curious… Does your technique reject the DC/electrostatic component of the e-field?