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Perimeter sender/receiver few questions

A

alda

Member
Today I placed 100m of perimeter wire. Measured resistence is 2ohm, so I used also 10ohm 50w resistor.
So I have 12V and 12ohm = 1A
Question is, if it's normal that resistor is very hot (you can't touch) when sender is running ?
When I go manually (by hand, motors off) with mower inside/outside, position is good detected, but when I start a motors, detection isn't working correctly.
It looks like there is a big noise from the motors. Is there any possibility how to decrease noise ? I know bigger distance from the motor is a solution, but any other like metal shield and etc ....
Thank you
Alex
 
In this article Kurzschuss explained something about the perimeter (but in German).
http://www.ardumower.de/index.php/d...oren-generator/1212-schwaches-perimetersignal
It looks like there is a big noise from the motors. Is there any possibility how to decrease noise ?
Zum Vergrößern anklicken....
Must do:
Drill ALL cables.
Connect coil direct to amplifier circuit (or use bnc RG174 cable http://www.ardumower.de/index.php/d...e-mit-stoerungen-an-der-empfangsspule#10009). Only connect ONE GND to amplifier circuit. Do no GND loop like in the article above.
In my tests, the coils must be 15cm minimum away from the motors to decrease the noise.


Maybe helps:
Use maybe shielded cable for sensors and connect schielding on one side to ground.
Suppress motor noise: https://github.com/Ardumower/ardumower/tree/master/Dokumentation/Motor Entstoerung
The problem, that the resistor gets hot is, that most energie are blown away in the resistor instead of perimeter wire.
See first link.
In my opinion, for 100m 1A is very big but I could be wrong.

Hope that helps you a little.
I don't want to translate all infos from Kurzschluss. If you are not able to translate correctly with google, don't hesitate to ask
:)
 
Hello Roland,.
thank you for your answer. What I already have to decrease a noise is :
-motor body grounded
-only one GND for amplifier
-coil directly to amplifier

But noise is still too high (looking on smag value)

What I can see as good working solution, is increase distance from motors to coil, but it's problem for me increase a distance from motors.

Question is, if the noise is going via cables or it's magnetic field. But if it's better with bigger distance, it looks like a magnetic field problem .....
Also strange is, that this noise isn't here with mow motor.

Alex
 
Hello Alex,

if the noise is going via cables
Zum Vergrößern anklicken....
Have you twisted the cable? Very important. ( above I used drill which was the wrong word)

Also strange is, that this noise isn't here with mow motor.
Zum Vergrößern anklicken....
Same in my robot. I think there is no problem in case the motor is monunted perpendicular and the field is 90° to the coils. And therefore the electro-magnetic-field has no influence.

Maybe you can show some pictures from the inside and coil mounting. How far is you coil away from the motors?

What I can see as good working solution, is increase distance from motors to coil, but it's problem for me increase a distance from motors.
Zum Vergrößern anklicken....
If you take a look at this picture: http://www.ardumower.de/index.php/d...eme-mit-stoerungen-an-der-empfangsspule#10009 the coil is maybe 5cm more away from the motors than your coil. And I think that is a total of 15cm from the motors.
On this picture you can see the twisted cable also.
 
Hello,
I did a tests with following results :
-twisted the cable - not working
-coil distance - yes working, but must be a far away

So I did a test with second motor shield :
I made a simple motor shield and place over motor :

WP_20170514_20_33_16_Rich.jpg


and here was a positive influence on the smag :

WP_20170514_20_32_40_Rich.jpg


I tested on one motor, but for both motors I tested simple plate :

WP_20170514_21_03_09_Rich.jpg


result was also good :

WP_20170514_21_03_01_Rich.jpg


stabilized :

WP_20170514_21_04_14_Rich.jpg


I think not bad

Alex
Attachment: https://forum.ardumower.de/data/media/kunena/attachments/1183/WP_20170514_20_33_16_Rich.jpg/
 
Zuletzt bearbeitet von einem Moderator:
So I spent some time with tests and mower rework with following results :
I changed ALL wires from normal to shielded - no major influence on the interference
I moved all electronics from the front to the back to have a motor driver as far as possible from the perimeter coil - no major influence on the interference
So only two things affect improvement :
1. Distance of the perimeter coil from the motors
2. Metal plate (only plate, cover not necessary) between motors a and perimeter coil

One question regarding regarding distance of the perimeter coil from the motors : Let say, coil is 10cm before the mower - is any possibility adjust how fast mower will stop when detect perimeter ? Because not cutted area around perimeter ? :

cut.jpg


.... I will continue with my tests ....
Alex
Attachment: https://forum.ardumower.de/data/media/kunena/attachments/1183/cut.jpg/
 
Zuletzt bearbeitet von einem Moderator:
perimeterTriggerTimeout is the time in ms to drive forward after crossing the perimeter before starting to drive back.
 
So shielding is finished.
I tested on the desk measured values (short loop with 10ohm resistor) and smag value with running motors with perimeter sender off is around 95.
What is strange, that value with running perimeter sender when I'm inside loop is around -1700, but when I'm out of the loop is 300. Normaly +-value must be same right ?
I also tried ADC calibration, but results are still the same.

Alex
 
Hi
Yes it s strange, on my mower the value at for example 5cm inside or outside of the area are the same 1200 or -1200 only the sign is opposite.
You say short loop . Maybe it s the problem. Try with 5m between the 2 wire
By.
 
Hi
When I say 5m between wires it's minimum a square of 5 by 5 m to avoid perturbation in signal.
But I really not sure it's the problem.
Are you sure your receiver is ok (shunt of the capacitor etc...)
By
 
Maybe you can try to invert the sender output to verify if the negative value is greater than the positive
 
I tried also values on my 100m loop and problem is the same. One value is higher then orher. ADC value after calibration is 518 and when sender is off, measured value is 0.
 
Hi
When you make the adc calibration the sender.need to be off.
In my mower at the output of the receiver there is 2.5 V so the Adc calibration value of 518 is perfect (half of 1024).
The mesure value of 0 is normal when sender is off.
Did you make the test with the wire invert at the output of the sender?
By
 
Sure I did a ADC calibration with sender off and charger off. When I invert sender, problem is the same but with + values. Mean it's changing if positive or negative value is lower. Question is, how detect if problem is sender or receiver? Sender and receiver I have a original from the shop.

Alex
 
Hi.
I think you put the scope directly on the output of the sender.
I can't find the unit on your scope Where is the 0V and what are the unit ?

At the output off my sender i have +8V and -8V

Here the file
senderscope_2017-05-29.jpg



But in your case i'am not sure the problem is the sender .
I think the receiver or a problem in the ADC.
With the console you can read some value like for example loopspersecond and by pressing v the perimeter value read.
Attachment: https://forum.ardumower.de/data/media/kunena/attachments/3545/senderscope_2017-05-29.jpg/
 
Zuletzt bearbeitet von einem Moderator:
Hi,
I also think that sender isn't a problem, but I want go step by step :

WP_20170529_10_21_21_Rich_2017-05-29.jpg


So it's +6V -6V

Strange is that with run mode I can see a "ghosting" (first picture in my previous post), but in stop mode it's ok.
If I will compare with pictures from Wiki, singal looks ok.

Scope was on the resistor which is in the loop.
Is possible set fix ADC value for analog perimeter input to 512? Maybe my value 518 after calibration is a reason.
Attachment: https://forum.ardumower.de/data/med...183/WP_20170529_10_21_21_Rich_2017-05-29.jpg/
 
Zuletzt bearbeitet von einem Moderator:
Hi.
Yes the first picture is Strange but maybe the scope ????
At the beginning you have trouble with motor,When you got the wrong value Did a motor rotate or all is stoped ?
Again are you sure the receiver is correctly change like in the WIKI (Shunt the capacitor ?).
I think The ADC calibration is not the problem .

Orientation of the coil ?? Can you take a picture

Good luck
 
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