Antennas in standard chassis: connected?

[JohanB]

Hi,
(Deutsche Version unten)

When attaching the antenna cables to the standard chassis, the outside of the antenna cable screw connects with the metal (conductive). If you attach multiple antenna's (XBee and WiFi) to the chassis, this means these antenna's are connected. Somehow, I don't think this is a good idea but I don't know much about antenna's.

Does anybody know and how did you mount your antenna's to the chassis?
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Beim Anbringen der Antennenkabel am Standardchassis verbindet sich die Außenseite der Antennenkabelschraube mit dem Metall (leitfähig). Wenn Sie mehrere Antennen (XBee und WiFi) an das Chassis anschließen, bedeutet dies, dass diese Antennen verbunden sind. Irgendwie halte ich das für keine gute Idee, aber ich weiß nicht viel über Antennen.

Weiß jemand wie du deine Antenne am Chassis befestigt hast?

Vielen dank
Johan

 

[ama]

Where did you mount your antennas? Given that everyone ought to have external antennas now with the metal mower bodies, I was surprised not to find any pictures of ardumowers with visible twin antennas.

 

[JohanB]

I mounted them in the side panels. In that way, when the cover needs to be lifted, the wires are not a problem.
in response to my own question: it appears that both ground connections of the antennas are connected to the common ground anyway. So, the common connection via the chassis is not an issue. As long as you remember that it’s grounded and don’t connect anything else, of course.

 

[ama]

Mounting on the side panels certainly solves the wiring for everything but the gps antenna. I was thinking of having the ESP32+gps boards and all 3 antennas on the roof plate (the boards obviously mounted on the inside). That way I would have 2 flat cables + the breaker cables going to the lid, all of those cheap and easy to replace. But perhaps mounting the two antennas elsewhere and accepting that the sensitive multiband cable has to be handled carefully when opening the mower is a better strategy.

 

[cat]

Where did you mount your antennas? Given that everyone ought to have external antennas now with the metal mower bodies, I was surprised not to find any pictures of ardumowers with visible twin antennas.

First I mounted them in the side-walls until on the first test-run one Antenna broke.
Then I moved them to the back wall underneath the top-cover.
So far they are safe there.

 

[cat]

When attaching the antenna cables to the standard chassis, the outside of the antenna cable screw connects with the metal (conductive). If you attach multiple antenna's (XBee and WiFi) to the chassis, this means these antenna's are connected. Somehow, I don't think this is a good idea but I don't know much about antenna's.

Very good question!

The more disturbing consequence is that the two aluminium front-pillars that are probably designed to supply the charing current (via the top screws) to the PCB 1.4 board are electrically shorted now! Uh Oh!

 

[JohanB]

@cat The front-pillars should never be used to conduct the charging current, as they are always electrically connected. The design for the charging station also features isolators for the screws to mount the balls on the cover plate. See https://wiki.ardumower.de/index.php?title=Charging_station#Install_the_charging_contacts So, these connections should obviously always be kept isolated from the rest of the mower circuit.

As I wrote: "As long as you remember that it’s grounded and don’t connect anything else, of course." Works well in my case, and I will be adding charging contacts soon. Of course, if you isolate the antennas as well, this is probably a safer way to avoid troubles in the future.

 

[ama]

Very good question!

The more disturbing consequence is that the two aluminium front-pillars that are probably designed to supply the charing current (via the top screws) to the PCB 1.4 board are electrically shorted now! Uh Oh!

How so? The board should be isolated from the alu extrusions by the 3dprinted spacers/holders.

I ended up adding my antennas as per 1.jpeg above. I hope they won't break off.

 

[cat]

How so? The board should be isolated from the alu extrusions by the 3dprinted spacers/holders.

I think that the PCB 1.4 is designed so that you can use metal screws instead of the plastic spacers there that connect to the CHARGE+ and CHARGE- via the aluminium-pillars to the top screws. This is a cool idea and would be necessary for a docking/charging station that the robot can automatically use.

How would you get the charging connections for a docking station to the outside now with the shorted pillars?

I ended up adding my antennas as per 1.jpeg above. I hope they won't break off.

They will break if the bot gets too close to a sidewall, flowerpot, etc. because they go beyond the wheel. Have some spares ;-)

 

[JohanB]

@cat the pillars are already electrically connected together via the screws to the chassis. You cannot use the pillars to conduct the charging current unless you take care to isolate them from the chassis. Even if you isolate the antennas from the chassis, this is the case.

Attached is a picture of my mower. The antennas are mounted on the side and for me that works well. Choose an option that suits you best

 

[goosst]

First I mounted them in the side-walls until on the first test-run one Antenna broke.
Then I moved them to the back wall underneath the top-cover.
So far they are safe there.

So if I understand correctly, you have mounted them under the cover without any issue on signal reception? (picture: https://forum.ardumower.de/attachments/ardumower-2-jpeg.3036/)
I would prefer to keep the height of my robot limited to get under a low fence ... .