As a hobby I try to receive 5.3 kHz radio signal, emitted by many commercial heart rate chest belts, to my Arduino microprocessor program through an analog digital converter port of Arduino chip, less than at 1 meter distance.
The signal sent ideally by the belt is 5.3 kHz burst of (sine?) wave during about 6 milliseconds once for each beat of the heart, and nothing is sent in the meantime.
The Arduino chip and the program can take 8-bit samples from the analog circuit hardware interface at the rate of about 20 kHz, and do some processing at 16MHz (e.g. filtering, limits comparisions, timing).The least significant bit would be minimum of 1 V / 256 = 4 mV.
Ancient crystal radio receivers used
1. a wire antenna,
2. an inductor
3. a capacitor (f = 1/(2*pi *sqrt(L*C))
4. a germanium diode (0.3 V )
5. ear phones
No external power supply, no amplifiers.
In this case no ear phones (5.) are needed. The diode (4.) can (?) be omitted also, because the software can find the ups and downs of the voltage converted to numbers in the microprocessor memory.
Crystal radios must have had the antenna signal voltage over 0.3 V in order that the earphones produce any sound (?).
That size of voltage would be enough for Arduino adc (analog digital converter) and program to work on, 0 - 1 V would be ideal.
A. Could we also omit the inductor(2.) and capacitor (3)? Do their work of filtering (tuning) in the software, provided Arduino has enough processing power. If trying this, which kind of antenna to use, exactly (!) ? (links?)
B. If using components 1, 2, 3, this should apply:
f = 1/ (2*pi*sqrt(L*C)) = 5.3 kHz
The components become large (smaller would be better) Anything to do for that? Antenna?
---
I have discussed the earlier phases of the project also here
The signal sent ideally by the belt is 5.3 kHz burst of (sine?) wave during about 6 milliseconds once for each beat of the heart, and nothing is sent in the meantime.
The Arduino chip and the program can take 8-bit samples from the analog circuit hardware interface at the rate of about 20 kHz, and do some processing at 16MHz (e.g. filtering, limits comparisions, timing).The least significant bit would be minimum of 1 V / 256 = 4 mV.
Ancient crystal radio receivers used
1. a wire antenna,
2. an inductor
3. a capacitor (f = 1/(2*pi *sqrt(L*C))
4. a germanium diode (0.3 V )
5. ear phones
No external power supply, no amplifiers.
In this case no ear phones (5.) are needed. The diode (4.) can (?) be omitted also, because the software can find the ups and downs of the voltage converted to numbers in the microprocessor memory.
Crystal radios must have had the antenna signal voltage over 0.3 V in order that the earphones produce any sound (?).
That size of voltage would be enough for Arduino adc (analog digital converter) and program to work on, 0 - 1 V would be ideal.
A. Could we also omit the inductor(2.) and capacitor (3)? Do their work of filtering (tuning) in the software, provided Arduino has enough processing power. If trying this, which kind of antenna to use, exactly (!) ? (links?)
B. If using components 1, 2, 3, this should apply:
f = 1/ (2*pi*sqrt(L*C)) = 5.3 kHz
The components become large (smaller would be better) Anything to do for that? Antenna?
---
I have discussed the earlier phases of the project also here
