Willkommen, Gast
Benutzername: Passwort: Angemeldet bleiben:

THEMA: Buried Wire Fence

Buried Wire Fence 3 Monate 4 Wochen her #1650

  • Dave
  • Daves Avatar
  • OFFLINE
  • Benutzer
  • Beiträge: 4
I am wondering why you choose 7.8Khz for the buried wire signal..? Is it possible to use say 38Khz.. If so what all would I need to change? Thanks...
Der Administrator hat öffentliche Schreibrechte deaktiviert.

Buried Wire Fence 3 Monate 4 Wochen her #1651

  • AlexanderG
  • AlexanderGs Avatar
  • ONLINE
  • Ardumower Sponser
  • Beiträge: 774
  • Dank erhalten: 351
Hello Dave,

-A- Why did we choose 7.8 Khz?
1. A lot of China robot mowers use the same frequency (Tianchen, Supoman, and compatibles). So, you can use an existing charger station of them which includes a signal generator of the same frequency.
2. The signal generator should be simple - because it's simple, it generates a simple square wave signal with multiple harmonics waves. That means it generates not only the 7.8 Khz main wave but also additional waves:

7.8 Khz - 1st harmonic wave (100% amplitude)
15,6 Khz - 2nd harmonic wave (12% amplitude)
23,4 Khz - 3rd harmonic wave (10% amplitude)
31,2 Khz - 4th harmonic wave (9% amplitude)
39 Khz - 5th harmonic wave (8% amplitude)
...
101,4 Khz - 13th harmonic wave (2% amplitude)

You can see the harmonics in the frequency spectrum (2nd graph) below.


signal5.png



The higher you choose the frequency, the more chances are that your harmonics enter a wide range used frequency (ham radio, radio broadcasting etc.)

We are working on a more complex signal generator that does generate less harmonics.


-B- Can I change the frequency?
You can change the frequency of the signal generator and the resonator amplifier (resistor R and capacitor C) in the sender and in the receiver circuits:

1. Change the frequency of the tone generator in the Arduino sender code:
tone(pinDir, 7800); <--- that's the frequency of the tone generator (I think the max. frequency the Arduino library can generate is 31767 Hz)

2. Adjust the coil/capacitor of the sender's resonator circuit, so that you get a minimum impedance at your choosen frequency (or in other words that the resulting resonant frequency is your choosen signal frequency):

You can use a resonant frequency calculator for this:
www.lautsprechershop.de/index_hifi_de.ht...s/t_schwingkreis.htm
www.deephaven.co.uk/lc.html
www.1728.org/resfreq.htm

Example (when choosing the original 7.8 Khz):
R=10 Ohm (Resistor)
L=33 mH (Coil)
C=0.012 uF (Capacitor)
=> resonant frequency calculator result: the minimum impendance/resonant frequency is at about 7.8 Khz (7999 Hz)

3. Adjust the capacitor of the receiver's resonator circuit, so that you get a minimum impedance for your choosen coil (or in other words so that the resonator works best at your choosen frequency):

Example (when choosing the original frequency 7.8 Khz and the original L=85 mH coil):
R=10 Ohm (Resistor)
L=85 mH (Coil)
C=0.0047 uF (Capacitor)
=> resonant frequency calculator result: the minimum impendance/resonant frequency is at about 7.8 Khz (7964 Hz)
Beitrag hilfreich? Dann unterstütze das Projekt indem Du den Ardumower Shop besuchst...
Posting helpful? Just support this project by visiting the Ardumower Shop...
Letzte Änderung: 3 Monate 4 Wochen her von AlexanderG.
Der Administrator hat öffentliche Schreibrechte deaktiviert.
Folgende Benutzer bedankten sich: autega

Buried Wire Fence 3 Monate 4 Wochen her #1655

  • Dave
  • Daves Avatar
  • OFFLINE
  • Benutzer
  • Beiträge: 4
OMG ... Thank-you so much for the extremely prompt and very detailed explanation.. I am very impressed with this project.. I have been working on my own mower for the last couple of years and this part of the project really plagued me.. I did have a working version of the transmitter/reciever and it worked well this summer but I feel like this project as a whole is much more detailed and put together.. I will be redesigning my system to utilize this software/hardware..

I do have one more question on the topic.. If the sender is using a 33mH inductor and a .012uF cap for a resonant frequency of 7999Hz .. Why not just use the same inductor and cap for the reciever? Why build a coil to 85mH?
Letzte Änderung: 3 Monate 4 Wochen her von Dave.
Der Administrator hat öffentliche Schreibrechte deaktiviert.
Moderatoren: autega
Ladezeit der Seite: 0.188 Sekunden
Powered by Kunena Forum
   
© Ardumower