Hi, i have built a mobile platform with two powered wheels at the front and a caster type wheel at the back so that it will travel around. There are whiskers on the front so that when it hits an obsticle it will reverse, turn and then go forward again. I now want to contain it in an area without walls.
My mother has a Mowbot which picks up a sinusoidal signal from a burried wire in the lawn and I thought that I could find out the frequency her robot uses so that I could run my robot inside her perimiter. This way I can consentrate on building a receiver and get it working without having to build a transmitter at the same time.
My Question :-
How do i find out what the frequency of the signal running round her lawn wire is ?
Get a scope outside and hitch a piece of wire onto the probe to act as an aerial (antenna). Ignore the 50Hz or 60Hz mains signal that you will also get - I assume the frequency you are looking for will be higher than that.
"The border wire creates a loop around your lawn which connects to MowBot’s garage which in turn is plugged into the mains. The wire carries safe electric current which MowBot detects as it passes over it, making it turn around and go in the opposite direction."
Thanks Dch & Willi.
1. I have borrowed a Frequency counter and will try putting a 1" coil of 10 loops on the aerial and see what frequency it picks up.
2. I tried the Mowbot people but they would not say what frequency was used. Hence why i need to find it myself.
If there are two signals being sent down the cable, will the frequency counter show them seperately or will it try to combine them. i have seen other designs using both one signal and others with two (one for border and one for returning to the garage).
Wow bananasiong, that is just what it does. Did you make the bot in the film ? what i want to do is find the frequency of the wire around my mother's garden so i can build a received to use her wire loop.
Any assistance you can give will be greatly received.
Ya, the perimeter wire is just a few loops of wires connected from the output of the 555 timer with a current limiting resistor. I made it to be around 10 kHz. Maybe your Mowbot is not using this frequency.
I doubt it's that high, induction loop sys are normally low frequency or very low frequency, (30kHz to 300kHz or 3kHz to 30kHz). Your frequency counter starts at 300MHz which is far too high.
Hi, any idea how i can measure a lower frequency if this it too high.
I am at a loss how i can find the signal i require. i can do the mechanical / programming bits (albeit slowly) but the electronics bit is a bit of a mystery.
Measure the signal at the "transmitter" e.g. where the wire loop goes underground.
First attach a voltmeter (so you know what you're dealing with) then the frequency counter. If you suspect that the signal is coded or there are multiple frequencies, use an oscilloscope.
Hi Hero, thanks for the note.
I have looked for a cheap low frequency Frequency counter but can only see them from 50Mhz. Have you seen any that would do the job or any ideas where i should look.
Hi the Frequenct Counter i borrowed was 1Mhz-gGhz.
If i understand correctly :-
1Hz = 1
1Khz = 1,000Hz
1Mhz = 1,000,000
I think i am looking for something between 50Hz and 80Hz. I will see what i get with this device, if nothing meaningful i will have to look at more expensive options.
You are correct but I don't think the system will be working at such low frequencies, it's more likely to be between 50kHz and 80kHz than 50Hz and 80Hz.
Hi, i am back. i received my IBQ2006ST Frequency counter in the post this morning and took a reading of the signal coming from the perimeter wire.
the reading was fluctuating between 73Hz and 80Hz with the aerial in line with the wire and up to 83Hz with the aerial at 90 degrees to the wire.
Could there be 2 signals going down the wire one in the low 70's and one up at 80Hz ?
I suppose i will have to build a receiver that i can tune into the frequency between 70 & 80Hz.
Any suggestions or offers of help with PCBs would be accepted - i have plans from a guy (his website) who has made one already.