I have 2 robot mower circuits that I want to switch between (my yard is too large for 1). I presently have it wired with a double pole, double throw switch where the positive and negative terminals are wired to their respective ends. It works just fine. I want to get away from a mechanical switch for a number of reasons.

I am wondering, can I go to a single pole, double throw switch? Can I join the negative terminals together so that the switch just toggles between the positive terminals?

If so, then I can replace my mechanical toggle switch with a bluetooth / wifi one and switch it remotely. My power supply provides 25.5 V @ 2A (I believe DC).

I need to find the correct part, but I was looking at something like this:
https://www.amazon.com/Shelly-Bluetooth-Automation-SmartThings-Compatible/dp/B0D8YPW46Y
https://www.amazon.com/Shelly-Automation-Compatible-shutters-required/dp/B09Y8ZG4K1 - 2 channel, I would have to programmatically operate this to ensure it is one or the other

If I read the label correctly, it can take 12VDC, 110-240VAC, or 24-48VDC. I'll update this once I find the right part, if I don't, then I suppose what I'd have to do is join "n" of these together and then in my app, I would enable 1 at a time. By join, I mean, share positive terminals, negative will be common across all switches and circuits.

I haven't been into electronics for quite some time and want to make sure I'm not going to end up with my hair smoking.

Thanks for your help.

 

It is not clear what you are trying to do.
You have two robot mowers, Robot1 and Robot2.
Each one is an autonomous battery operated mower.

Where does a switch come into the picture?

 

Sorry for not clearly stating.

No, I have 1 robot mower, but 2 circuits. I presently use a mechanical toggle switch to tell the mower where to go.

 

Sorry for not clearly stating.

No, I have 1 robot mower, but 2 circuits. I presently use a mechanical toggle switch to tell the mower where to go.

What do you mean by 2 circuits?
Where are the two circuits located?
What is the function of the two circuits?

Are you trying to switch 24 VDC battery power from one circuit to the other?
Then, yes, you can connect negative battery terminal to both boards.
Use the wireless relay board to switch positive battery power using a SPDT relay.
DPDT relay will also work, using only one single pole of the double pole relay.

Edit: Your wireless relay board must be powered from a battery source on the robot.

 

I will address the first 3 questions:
By 2 circuits, I mean, I have 1 circuit for the front yard, and 1 for the back.

Yes, it was a bit of a pain to sort out. I can share more details if interested, I spent 1 whole season of manual cutting time arranging the circuits and that is no joke.

Basically, I have built in some overlap where both circuits cover the same area, so the mower will end up cutting the same area 2x (in reality, it is random, but still, it is less efficient). I had to arrange the wire within the manufacturer's specs to ensure the mower can get back into the docking station just fine, "see the wire", etc. In essence, imagine my yard as a Venn Diagram with 2 circles and the intersection is the area the mower has to cut twice as a result.

I split the yard into 2 circuits because even though my yard size is less than the manufacturer's specs, after routing around trees and other obstacles, it apparently was too long for the mower to detect the signal and would randomly stop working in the middle of the yard. It worked most of the time, but it wasn't reliable. Secondly, after having done so, it is also somewhat nice because the backyard grows a bit quicker than the front and that allows me to easily prioritize cutting it more.

I am switching the power supply from the line. The power supply converts AC to 25.5 VDC @ 2A.

 

I think there is a gross miscommunication.

The name of this web site is All About Circuits.
When we use the word circuits, we generally are referring to electrical and electronic circuits. Hence, I thought that you were referring to circuit boards on your robot mower.

It is now my understanding that your use of circuits refers to the electrical perimeter wires that are laid into the ground to set the limits of the range of the robot mover.

Is that correct?

Hence, my apologies. Your usage of the word circuit is correct. It is simply that the word has different meanings in different contexts.

1) Circuit - a line, route, or path that starts and finishes at the same place.
2) Circuit - an established itinerary of events or venues used for a particular activity.
3) Circuit - a complete and closed path around which an electric current can flow.
4) Circuit - an electrical or electronic diagram or implementation of such diagram.

 

Yes, by circuit, I meant the perimeter wire.

My question was mainly around wiring the switch in this case to make sure I was doing it safely. The power source is outputting 25.5 VDC and I mainly wanted to know if it was safe to join the negative terminals together such that I could simply use the wireless switch above to toggle between the different perimeter wire runs.

 

Ignore everything I have said before.

The base station connects to the perimeter wire via two terminals. The perimeter wire starts at one terminal, loops around the lawn, and ends at the second second terminal on the base station. The current supplied to the perimeter wire is low voltage high frequency AC.

You can switch from one perimeter wire to the other using a wireless relay with DPDT contacts.
You can join the two wires at one terminal and switch between the two wires with SPDT contacts.

 

Ok - that leaves me with one question. Can I use the wireless device linked above then or will the low voltage, high frequency power not work with the Shelly 2 Plus PM or harm it?

The power supply isn't clear to me whether it outputs AC or DC and that voltage leads me to believe it is DC.

 

The 25.5 VDC @ 2A output is for charging the battery on the robot mower.

As far as I can tell, the Shelly Plus 2PM will not work for this application.
You need a relay where the relay contacts are isolated from the incoming power source.

 

Ah ok, so, then the only way for the Shelly to work then is if I power the Shelly independently.

Ok, I guess that makes sense, the Shelly can handle AC and DC, so, if the power source is 25.5 VAC that wouldn't cook the Shelly. The problem is that it needs its own power to ensure it can both charge and power the perimeter wire.

 

Ah ok, so, then the only way for the Shelly to work then is if I power the Shelly independently.

Ok, I guess that makes sense, the Shelly can handle AC and DC, so, if the power source is 25.5 VAC that wouldn't cook the Shelly. The problem is that it needs its own power to ensure it can both charge and power the perimeter wire.

No.
The mower base station powers the perimeter wire.

What you need is a wireless relay board that is powered from 120 VAC line supply.
Then, the output of the relay board has to have isolated relay contacts.
You can do this with a Shelly module and an external relay but that does not make sense to have two relay boards.

 

Here is a relay with WiFi connectivity.

Amazon.com: URURTM 1CH Dry Contact WiFi Relay Switch Module,DC 12/24V AC 100-240V,Tuya Smart Life app,Compatible with Alexa,Google Home : Tools & Home Improvement

 

I cannot find a remote relay switch that is AC powered.

Here is one that is DC powered. You will need to get a DC wall-adapter to power the receiver.

https://www.amazon.com/ZHOFONET-Control-Wireless-Contact-Security/dp/B09LQ6Q9VV/ref=sr_1_13_sspa

 

Thanks. I appreciate all of your help, I think I *might* be understanding.

1. COM - connect "+" terminal of mower power source
2. NO - connect "+" terminal of front yard perimeter wire
3. NC - connect "+" terminal of back yard perimeter wire (by default I want the back yard to be cut)
4. L - connect hot AC wire
5. N - connect neutral AC wire
6. S1 - not connected?
I could optionally connect this to something else where it would then be energized by 110VAC

7. "-" terminal of mower power source connected to all "-" terminals of perimeter wire

Is that correct?

The second link would be fine I think as long as the relay itself isn't consuming a huge amount of energy. I would think that would be preferable. Wifi / bluetooth isn't critical, just as long as I can toggle it without having to open a watertight box.

 

As far as I can tell the Shelly units will not work.

 

I measured the output from the power supply and on my multimeter's range of 200VAC, it measured .7. On 200 VDC, it measured .2. The power supply itself is labeled in DC, so I suspect that my multimeter is unable to measure it accurately because it is a high-speed switching power supply which I presume would look like a square wave and aid in creating a signal for the mower to pick up.

I looked at the Shelly units more and the wiring diagram on their site and fingers crossed, think it should work:
https://kb.shelly.cloud/__attachments/243531777/Plus 2PM DC wiring diagram-20240528-134203.png?inst-v=18a9fbc2-71ba-4b1c-be6a-5d99df125bc9

The 2 channel one is looking for 24 VDC+- 10%, so it *SHOULD* work. Oddly enough, the 1 channel model accepts 24VDC - 48VDC, but does not have any such pins for NO or NC, just switch.

I suppose we'll see.

Again, it'd be easier for me to have a relay where I could wire a "NO" and "NC" since that is what I want in this case.

 

No.
The Shelly unit accepts an input voltage and then relays that to the output.
That is not what you want.

You want to switch the output of the base unit to the perimeter wire.
Look for a relay that states dry contact relay and has NO, COM, NC terminals.

 

Hmm, let me think about it.

The mower power source does indeed go directly to the base / docking station, then I connected the docking station where I would normally connect the perimeter wire to the switch, positive, and negative respectfully.

Then, from the switch, I have each section connected. I think it is just a straight pass through, I suppose I'll find out soon.

Ah, perhaps I should disconnect the power source from the base station and measure that output directly. That would let me know if there is more going on in the base station than meets the eye.

 

Yes, you're right.

The output from the power supply is indeed DC, but what is sent to the perimeter wire is AC.

I also miscommunicated base station and mower power source. In my head, I thought I wired the power source directly to the switch, but I'm confused (I did this about a year ago and was thinking it will be a pain and I'll eventually want it wireless).

So, back to your earlier post, then, will this device work:
https://www.amazon.com/URURTM-Contact-Switch-100-240V-Compatible/dp/B0DM1BYRPS

Then, if so:
1. COM - connect "+" terminal of mower base station
2. NO - connect "+" terminal of front yard perimeter wire
3. NC - connect "+" terminal of back yard perimeter wire (by default I want the back yard to be cut)
4. connect "-" terminal of mower base station with "-" terminals of back and front yard

5. L - connect hot AC wire
6. N - connect neutral AC wire
7. S1 - not connected?
I could optionally connect this to something else where it would then be energized by 110VAC