Paradise Robotics Forum
Robotic Lawnmowers => Lawnbott => Topic started by: roninwar on August 11, 2011, 05:48:37 PM
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So as some of you may remember from the other forum, I have a rather large yard - over an acre. I have also had problems with dead zones in my back yard - which is about 85% of the total space. I have fixed that particular problem by investing in a signal booster and mapping out "islands" with the perimeter wire. That has worked well except that these little islands require some maitenance in the form of my weed eater.
Now the center of the yard, as you all know, does does not get as much attention/cutting as compared to the areas around the perimeter wire. This is much more noticeable when the area is large. So what I decided to do was invest in another power supply and signal generator to form another zone inside the larger one which has the signal booster. This second perimeter wire I ran just like one of those islands that was done with the original.
I have spaced the wires from 5 inches, 8 inches, and 12 inches apart - when at 5 inches the signals tend to cancel out and the bot keeps going through the "island" wire as if it's not there. With the other two though it does something totally unexpected from my little knowledge of electricity and signals, ect.
The robot would encounter the wire, back up, go straight forward until it hits the wire(s) again, and repeat until I get tired of watching. What I was expecting was what happens with the original perimeter wire and the islands created - where the bot hits the wire, backs up, and turns a little prior to going forward again.....
Does anyone know what I am talking about and is able to explain to me why?
I wish I could include a drawing as it would make a lot more sense...
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You need to switch the polarity of the second zone. That's my guess. The behavior you are describing sounds like what I saw when I was testing my bot outside the parameter (sending it down the block in the middle of the street).
The bot doesn't know what side of the wire it is on, it just knows the direction of the signal. So, it will "bump" and go on the outside if you start it on the outside. But, I believe, if you start it on the inside, and it thinks it went over, before giving the "out of bounds" error, it will back up and try to get itself back inside. I'm guessing when it backs up, it detects the signal from the primary (telling it that it is inside the parameter again) and begins to mow.. then hits the secondary wire and thinks it fell outside again.
Of course, this is all speculation.
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roninwar,
Here is how you can post a drawing/picture etc.
To Post a picture/drawing:
!. Hand draw your layout on a sheet of paper.
2. Scan it in and save as a .jpeg file.
3. Go to:
http://tinypic.com/
Click on the Browse… button
Find your .jpeg file and select Open (on a Mac)(whatever on a PC)
The location of the file on your computer will show up in the File: window
If it is the correct file you wish to upload then click the UPLOAD NOW! button.
(http://i53.tinypic.com/f1l4j.jpg)
You will get a screen such as this one asking you to enter the scrambled code.
Enter the code and click on UPLOAD NOW!
(http://i53.tinypic.com/21npbb4.jpg)
You will get four addresses that you can used depending on your requirements.
Select the second one (IMG Code for Forums & Message Boards) and paste it into your Forum message.
Simple as that, hope this helps.
Note: If you find an error let me know so I can correct it.
(http://i53.tinypic.com/dra1lh.jpg)
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Thx guys.
I've been kind a busy lately - hopefully I can get a pic uploaded soon.
Regarding the polarity(?) - I did switch the two around - same thing happens -
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Hi, I cannot imagine that two signal generators on the same yard would work unless you are using them one at a time. The robot will sync to one or the other generator, not both, and if both are on at the same time, they could interfere with eachother (very likely). I hope the dealer you purchased the power supply and booster from did not mislead you. If so, I suggest returning them.
Robotlady
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hmm. thought the signals should be ok as long as they are the same frequency...no dealer input
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Not sure, but could you take a larger area and break it up to form pseudo-zones? The boundaries would be the standard 10 inches in width so that it would occasionally mow when it returns to base.
Something like this
-----| |---------| |-----------|
| | | | | |
| | | | | |
| | | | | |
| -- - |
| |
---------------------------------
The two middle boundaries would be 6 feet from the bottom. This would be one zone, but the bot would spend more time bouncing back and forth.
This help?
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My vote is to nix the second PSU/Transmitter and run two switches or relays. Double wire your yard from the charging base and call it a day. I don't see why something like this wouldn't work:
(http://www.jzdocs.com/gallery/main.php?g2_view=core.DownloadItem&g2_itemId=1747&g2_serialNumber=2)
The only negative I can think of is that you would be wasting power when the relays are energized. If you don't mind running more wire, you could probably use a single DPDT switch (or relay) and wire it strait from the charger so that you only have one switch to flip (or relay to activate) and your done. You might even be able to mount it on top of the charging base.
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@roninwar, I understand that it may seem logical that if the two signal generators are at the same frequency it would work. However, they actually are not at the same frequency. Each transmitter will have an independent crystal oscillator to create the communication frequency. It is virtually impossible that the two oscillators will be at exactly the same frequency. The difference may be undetectable, but there will still be a difference by a tiny amount. I would expect the receiver to tune to one of them and not the other.
Another problem that can happen is a beat frequency could be created. When two signals of slightly different frequencies occur in the same place, the signal waves can add up in a way that creates a new, different frequency, called a beat frequency. The beat frequency could interfere as well.
Maybe I am wrong, but since it is not working these issues could explain why...
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Here is a layout that breaks a yard up into 6 parts. It uses the 'boot' method of keeping the bot into the area and allowing for a fast return when the time is up. It does require that set times are established so the timer is in sync with the bot. It also requires a lot of wiring but what the heck, it's Summer, ya have nothing to do.....well.....
(http://i56.tinypic.com/sym1pf.jpg)
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Wow, impressive! Much more sophisticated than my idea :). Is the 1/4 gap the width between zones or length between the border and where the wire broadens? Can you explain why this is set this way. Do you ever have problems sneaking out of morning area1 and morning area2-by the 1/4 inch gap?
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This idea has been kicked around quite a bit on the 'other' forum so most of the old hands have seen it before. One of the guys came up with the 'boot' and it really works. I didn't get into the details of the boot for the above reason. However I'll point out the finer points here for everyone who doesn't know about it.
The wires going to the top of the boot can be touching each other (I show 1/4 inch gap between them).
They shouldn't be much more than 3 to 6 inches in length before turning to form the side of the boot. Remember, the bot does it drunken sailor walk varying from side to side of the perimeter wire by about 3 inches. The 6 inches is a safety factor… The boot is nothing more than a skinny flower bed that you have wired around. And, yes, the bot can get lined up so it goes right through that small area. However, it has to be a straight shot, soooo, if you were to lower the perimeter wire down about 3 inches about 3 feet before the boot it would hit the perimeter wire and not go through.
The sides should be between 10 and 12 inches apart. I found that 8 to10 inches fits the 3200 models. Robot Lady says the 12 inches is better for the 3500 models. When you first layout your yard test it by making the bot hit the sides. Vary the distance to fit your bot. It stands to reason that the closer the wires are the more grass that will be mowed. Too close and the bot escapes into the next area.
At the toe the gap between it and the outer perimeter wire should be between 3 and 6 inches. The top of the boot can be 4 inches in length. If the top and bottom are too close the signal will be cancelled, so keep the bottom parallel with the outer perimeter wire. I show it at an angle which is wrong. The bigger the gap the more chance the bot can escape to the next area.
How this thing works is really neat. When it's time for the bot to return and it hits the front side of the boot it turns towards the toe, tries to make the sharp turn back at the end of the toe, overshoots, and catches the bottom outer perimeter return wire. Just what you would like for it to do since it's returning, right. If it's in the center area and hits the back of the boot it either tries to follow the wire around the flower bed, there by ending up at the toe. Or it hits the upper outer perimeter wire, runs over to the next boot and ends up at it's toe.
The drawing is NOT to scale as we are talking about Roninwar having a 1 acre lawn. So, in his case each area is 1/6 of an acre. The boots will be quite a ways apart.
If I get a chance I'll redraw it and edit the posting with a new drawing.
Almost forgot:
In Area A 1 at start up the bot backs out, spins it's blade up to speed, and either start to mow or go around the charger to find the perimeter wire.
When the switch is set to mow in the Morning it follows that procedure.
When the switch is set to mow in the Afternoon it does the same except it runs into the B wire and is blocked from mowing in Area A 1. Or it hits the wire and follows it to the other two B areas.
The wire coming from the switch can be almost along side the charger house until it gets to the entrance then it should leave room for the bot to turn around should it come back into that area as it mows the B area 1.
I've never used this set up so you're on your own with building the switch and getting a good timer that will last the season. Maybe one of those xmas tree timers.
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wow Toolbelt.... :o impressive.
It really looks like I may end up with too much wire for even the signal booster to handle, don't you think?
I may have forgotten to mention that there's another 1/4 acre in the front of the house...
If it ends up to be too much wire maybe I can use the second signal transmitter for the front of the house...manual carry every 3rd day or so...
Has anyone actually completed this layout? I never came across this discussion on the other forum.
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Even though it requires a lot of wire it cuts the amount of wire that has a signal traveling through it in half. So, you may not even need the signal booster....
Oscar the Lawnbott came up with the boot so search his postings.
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I replaced the layout with the new drawing. The bump out is nothing more than the wire NOT running is a straight line. The bot needs to be lined up with the gap at the top or bottom of the boot in order to make it through. The bump out will hinder that from happening.... it's say here in fine print at the bottom of the page..... ::)
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I will give this a try later this season when the weather is not too hot.
The only concern is the switch...
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I can not seem to come up with a way to make this switch work... What can I use?
toolbelt, can you provide me with a link to Oscar's original post/thread from the other forum?
I think this layout would do wonders for my back yard (as there are areas in the center that the grass is very long, despite the robot spending most of everyday there (extra battaries)).
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I don't understand your question. If you are talking about parts etc for the switch, I suggest you go to Radio Shack and ask them to sell you a switch that fills the drawing requirements that I posted. It may not be a 9 volt one but you would still need a transformer to provide the DC voltage for it. When the timer switches from OFF to ON the transformer would provide DC power so the switch would activate switching from Line A to Line B. When it switches to OFF the switch would go back to normally closed to Line A.
Here is an old link to one of the postings from which you can do some searching for his original posting. This link covers most of what was discussed. If you go directly to the old site the forum link does not exist (I didn't see it if it was there) Oscar came up with the boot/toe thing prior to this posting. http://www.bamabots.com/board/index.cgi?act=ST;f=1;t=218;st=0
The layout should also work even if you have a 3500 and run it backwards around the perimeter wire to a zone.
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Hi All,
I recently found out the maximum wire length with a signal booster is 1,000m or 3,280ft. A general recommendation is to use a signal booster when the wire length is greater than 600m/ 1968ft, but I have seen the need at 1500 ft as well (perhaps in that case the customer also had a loose connection).
If the wire length exceeds the maximum length, the strength of the signal will go down, but since the configuration reduces the distance the signal has to travel it **might** make up for it. At some point, though, the signal will become too small for the Lawnbott receiver to lock onto it and it does not matter how much cancelling you have. It is strictly dependent on wire length. All you could do is experiment and see if it works.
Also, using one robot transmitter in the front and the other robot's in the back is an excellent idea. Just make sure the one not in use is turned off, or bear in mind that if you leave it on you might see some issues.
If you try the wiring configuration to see if the "no signal" performance improves, I would be very interested to know how it turns out.
Robotlady
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Hey Toolbelt a big thanks for the boot layout. I have been having the no signal problem for some time now and the same poor mowing in the center of the yard. My back yard is 500' by 100'. I have recently installed a 10" by 180' tongue through the center of the yard. I still get some loss signal events, but not enough to impede the mowing. I have been thinking of doing something like this and not being one that reinvents the wheel will install your layout. Thanks Mel
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Your welcome, but a ton of the credit goes to Oscar the Lawnbott who came up with it.