Stationary relay nodes for newbies

#1

Why should I set up a stationary relay node?

The best reason is to increase the coverage area of the goTenna Mesh network near you. There are benefits on multiple levels: (1) You benefit yourself, since you immediately increase the reach of your own goTenna Mesh devices by enabling a “hop” between your device, the stationary relay node, and your intended recipient. And if you set up multiple stationary relay nodes – each one spaced a good distance apart, but within the range of another stationary relay node – you enable your goTenna Mesh device to achieve multiple hops between you and your intended recipient – extending the effective communication distance. (2) You benefit other goTenna Mesh owners in your area because your stationary relay nodes will handle hops to and from their devices. (3) The very presence of a stationary relay node in your area increases the value of goTenna Mesh devices to others, thereby promoting adoption of this technology by your neighbors. The more prevalent the mesh is in your area, the greater the likelihood that others will acquire their own devices. They may even establish their own stationary relay nodes, extending the reach of the mesh even further. (4) Your purchase of extra goTenna Mesh devices benefits the pioneering goTenna Mesh product development team, enabling reinvestment of profits to develop future product enhancements and ever-more-capable product lines; (5) You increase the incentive for third-party software developers to create new software apps that unlock the vast potential of this nascent technology. In turn, those new software apps raise the utility and value of your goTenna Mesh devices to you!

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#2

Okay – you’ve made me a believer in the benefits of establishing my own stationary relay node, and I want to promote the adoption of this technology in my local area. My problem is that I’m not a techie, so I need someone to provide step by step information on how to do it. Where do I start?

You’re in the right place. The goTenna Mesh Community contains a wealth of knowledge and connects you with the product development & support team as well as other enthusiastic users, experimenters, and third party software developers.

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#3

What is needed to setup a stationary relay node?

The answer is “it depends on the configuration that you choose to setup”. There are many different configuration approaches, each with their respective pros and cons. Here are a few approaches, listed (roughly) in order of increasing complexity…

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#4

Configuration 1:

The most simplistic approach is: (1) Charge up an extra goTenna Mesh device. (2) Turn on the device by holding down the power button until the light comes on, then release the power button; (3) Triple press the power button and watch for the light to turn on. (4) Triple press the power button again to confirm the request for relay mode. If relay mode activation was successful, the light will flash 3 times and then the light will turn off. (5) After the light turns off, you can confirm that the device is in relay mode at any time by pressing the power button briefly one time. The light will flash three times to confirm that relay mode is activated. (6) To maximize the effective range of the relay node, keep it in a vertical orientation, and raise it to an elevated position. The higher the elevation vs. the surrounding terrain, the better the effective range of the device. If you’re keeping it indoors, you can place it in a window on the top floor of your building, in the attic, etc. If you’re placing it outdoors, you can use a string tossed over a tree branch to raise it high up off the ground.

Note that this most basic configuration will require you to retrieve the stationary goTenna Mesh relay node and replace it with another fully charged unit about once per day, because the internal battery powers the device for about 24 hours of operation before the charge is depleted.

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#5

Configuration 2:

To avoid the burden of performing a daily retrieval for recharging, a more desirable approach is to use an “always on” external battery and a micro USB cord to supplement the power to the relay node, thereby extending the period of time before retrieval & recharge are necessary. Rechargeable lithium battery packs made for recharging cell phones are popular choices. Again, make sure that any such battery you are considering using has an “always on” setting so that it doesn’t turn itself off after it tops off the charge on the goTenna’s internal battery. Some good options are available here: https://www.voltaicsystems.com/battery-packs, but this is just one manufacturer’s options. If you shop around, there are others. The selection of an external battery should also consider how many days of relay node operation you want to achieve before you’ll have to retrieve and recharge the goTenna Mesh and its external battery.

The goTenna Mesh’s internal battery capacity is 589 mAh. To power the goTenna Mesh for 7 continuous days, you would need an external battery pack with a capacity of approximately: 6 x 589 mAh = 3,534 mAh. Assuming you start the stationary relay node with a fully charged internal battery in the goTenna Mesh unit, you’ll get 7 days of operation before the internal and external battery are depleted and require recharge. Similarly, if you want to power the stationary relay node for 30 days, you’ll need to start with a fully charged goTenna Mesh, and a fully charged external battery pack with a capacity of 29 x 589 mAh = 17,081 mAh.

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#6

Configuration 3:

To COMPLETELY avoid the burden of retrieval & recharging, an even more desirable approach is to set up a persistently-powered stationary relay node. The easiest method to provide persistent power is to connect the device to an A/C electrical outlet. You’ll need a USB A/C adapter and a long micro-USB cable. Plug the A/C adapter into an outlet on the top floor of your building, or in your attic, or on your roof (if you have a weather-proof outdoor A/C outlet on your roof), and connect the micro USB cable between the USB A/C adapter and the goTenna Mesh device.

Power the unit on and activate relay mode, then place it in a vertical orientation where it has elevation and good visibility. Note that if you place it in a location where it is exposed to weather, additional precautions are necessary to prevent moisture ingress at the electrical connections. There are various ways to prevent it. Most involve using a watertight plastic box capable of enclosing the goTenna Mesh device. A hole is drilled through the plastic box to permit pass-through of the micro-USB cable to the goTenna Mesh unit. The gap between the drilled hole and the sides of the USB cable is filled in with a tight-fitting rubber grommet, or a waterproof self-curing sealant such as RTV, silicone caulking, coax-seal, or shoe goo. The same approach is used to permit pass through of the other end of the USB cable to the USB A/C adapter that is plugged into the weather-proof outdoor A/C outlet.

As long as your A/C adapter outlet provides uninterrupted power, your goTenna Mesh device will stay powered on in relay mode, so it eliminates the burden of periodically retrieving and recharging the relay node and/or external battery. If, however, external power to the relay node is lost, AND the internal battery in the goTenna Mesh unit is permitted to completely discharge, the unit will not turn itself back on once external power is restored. The power button on the goTenna Mesh will need to be pressed to turn the unit on, and then the normal procedure will need to be followed to place the unit back into relay mode.

This inability of the unit to restart itself makes it imperative that external power interruptions do not last long enough to permit the goTenna’s internal battery to completely discharge. Should that happen, the stationary relay node will be out of service until it is accessed by someone to manually power it on and place it into relay mode again.

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#7

Configuration 4:

In many instances, an A/C electrical outlet won’t be available, so a different energy source will be needed to persistently-power the stationary relay node. The most common approach is to use a solar panel to charge an “always on” external battery pack, and to connect the external battery pack to the goTenna Mesh by a micro-USB cable. The external battery pack selected will need to be capable of simultaneously accepting the charge current from the solar panel, and sending the discharge current from itself to the goTenna Mesh unit. Not all battery packs can operate in this manner, so make sure your external battery can do this before using it in your setup.

Naturally, there are a number of questions that arise when you consider setting up such a system. “What power generation output do I need from my solar panel to keep my external battery pack from fully discharging?” and “How do I determine the external battery storage capacity that I need to ensure that the goTenna Mesh never loses power?” These questions will be answered in turn.

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#8

What power generation output do I need from my solar panel to keep my external battery pack from fully discharging? The answer is that it depends upon three considerations: (1) Your geographic location; (2) The orientation and quality of sun vs. shade throughout each day of the year; (3) The highest number of consecutive overcast days anticipated during the poorest power-generation month of the year for your location.

Fortunately, there is an excellent article with a link to a free online photovoltaic calculator that can help you calculate your needs, thus avoiding the costly and time-consuming process of experimenting to determine them through trial and error: https://www.voltaicsystems.com/blog/estimate-solar-irradiance-iot-device/

When entering input to the photovoltaic calculator, use the “off-grid” tab of the calculator. Enter the solar panel’s peak output in watts into the field labeled “Installed peak PV power [Wp]”. Enter the external battery’s storage capacity in watt-hours into the field labeled “Battery capacity [Wh]”. Enter the discharge cutoff limit for the battery into the field labeled “Discharge cutoff limit [%]”. If you don’t know the discharge cutoff limit for your battery and you are using a Lithium ion polymer battery, a conservative assumption is to input 40 into that field. Enter the power consumption per day in units of watt-hours into the field labeled “Consumption per day [Wh]”.

Since the goTenna Mesh device’s internal battery has a storage capacity of 0.589Ah, and the battery voltage is 3.7V, the amount of power you would need for one day is 0.589Ah x 3.7V = 2.1793Wh. That’s the power you would need if the energy conversion between the output of the solar panel to the input of the external battery, and back again to the output of the external battery, to the input of the goTenna Mesh was 100% efficient. In real world conditions, the energy conversion is far less than 100% efficient. The linked article states “With lithium batteries, we typically assume 50% of that power is lost going into the battery and back out to the device. That power loss comes from heat as electrical energy is transferred to chemical form and back again, as well as from regulation.” If you want to assume 50% efficiency due to energy conversion and regulation, then you’ll need to adjust your input to the photovoltaic calculator. You would enter “4.3586” into the field labeled “Consumption per day [Wh]. (That is 2 x 2.1793Wh = 4.3586Wh)

Next, enter the angle that the solar panel is raised above horizontal into the input field labeled “Slope [degrees]”. As noted in the linked article, the optimal angle for power production varies with month and geographic location. Be sure to recalculate the power production at various slope angles to determine the optimal slope for the worst power-producing month of the year, which will be December in the northern hemisphere, and June in the Southern hemisphere. If you exercise the photovoltaic calculator for Brooklyn, New York, you’ll find the optimal slope in December is a tilt of about 70 degrees up from horizontal. Next, enter the Azimuth angle in the input field labeled “Azimuth [degrees]”. In the Northern hemisphere, if you are able to orient the solar panel so that it is aimed directly to the South, that will provide the best power-production. In this case, enter “0” into the Azimuth input field. Finally, click the button labeled “Visualize Results” to obtain a bar graph that illustrates results expected for each month of the year for the power consumed (labeled “energy output”) and for the excess power delivered by the panel (labeled “energy not captured”).

One final consideration: If the solar panel will not have an unobstructed view of the sun throughout the day each day of the year, you will need to scale down the power output value you enter for the solar panel in the photovoltaic calculator. (i.e., if the sun tracks behind trees, buildings, and/or clouds during the course of the day, you’ll need to make a conservative assumption about the reduction in power production that will be output from the solar panel to the external battery.) Let’s say that you know the panel will be placed in a location where it will only have direct line of sight to the sun for 50% of the daylight hours on a clear day. Let’s also say that passing clouds will cause intermittent exposure to the full intensity of the sun during the periods of the day when there should be an unobstructed line of sight. You might make the conservative assumption that the output power of the solar panel is only 25% of the rated peak value, and adjust the input field in the photovoltaic calculator accordingly to help you understand expected performance under these conditions. The idea is to take these things into consideration to ensure that the panel you purchase has a high enough energy output to prevent full depletion of the external battery pack and the goTenna’s internal battery. As previously mentioned, you need to keep your relay node up and running continuously, or a manual intervention will be necessary to depress the power button and to place the device in relay mode once the solar panel recharges the batteries in the system. For this reason, it’s best to err on the side of selecting a solar panel that produces too much, rather than too little power. (It will save you the aggravation of periodically visiting your stationary relay nodes to reset them. Depending on the difficulty of accessing them, this may be “priceless”.)

In the end, you’ll still need to try out the system you design to verify adequate performance in the varying conditions at your location, but the photovoltaic calculator and the tips above will help you select the right solar panel for your needs the first time.

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#9

How do I determine the external battery storage capacity that I need to ensure that the goTenna Mesh never loses power, in conjunction with the solar panel selection that I have made using the photovoltaic calculator?

You need to consider the maximum number of days of overcast weather in your location expected during the month of the year that produces the least amount of power from your solar panel. So in the Northern hemisphere, you should be looking at the most consecutive days of overcast weather in the month of December. In the Southern hemisphere, consider the most consecutive days of overcast weather in the month of June. This type of information can be obtained by querying a historical weather database for your location. One such database is linked here: https://weatherspark.com. Studying the historical data will allow you to estimate the worst case. If, for instance, you are in Brooklyn, New York, and the historical data indicates that the highest number of consecutive days of overcast weather on record in December was 15 days, here’s a conservative method for determining the external battery storage capacity you’ll need to ensure that your goTenna never loses power.

You start with the conservative assumption that the energy output from your solar panel on an overcast day is zero. This means that you’re assuming your external battery is losing power at a rate of 2.1793Wh per day. In a 15 day period, the external battery would lose 15 x 2.1793Wh = 32.6895Wh of power. A 44Wh external battery, such as this one: https://www.voltaicsystems.com/v44, used in conjunction with the goTenna’s 2.1793Wh internal battery, would keep the system powered through the rough patch of weather, and when the sun once again emerges, the solar panel will gradually recharge the external battery pack. If you are in Brooklyn, New York, using a solar panel with a 6 watt output, a slope of 70 degrees, an azimuth of 0 degrees, and you have unobstructed line of sight to full intensity sun throughout your December day, you can expect to replace the 32.6895Wh of power that was drained from the external battery pack in about 3.1 days of full intensity sun exposure. Then your system will be ready to endure just over 21 days of zero energy production from the solar panel without the goTenna Mesh ever losing power.

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#10

That pretty well sums it up in terms of panel, as well as battery pack, sizing. The calculator gives what I consider to be minimum values. In making your final hardware choices, go for the next size bigger IMO and experience. At 40 degrees North latitude, I’ve found that a 6W minimum size panel is what you need as reliable starting point.

For more info on such basic user friendly set-ups, along with lots of pics, visit the UMESH thread: Urbana, Illinois, Now a goTenna Mesh Ambassador City!

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#11

@MeshTheWorld Wow, will have to come back after work hours to read everything but thanks for this primer & call to mesh! :slight_smile:

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#12

I have one stationary set up and connected to A/C power but I would love to know if there is a way to see if I am actually doing anything to help anyone. I know I’m the long run someone will use it, but how can I get a stats sheet listing the amount of jumps passed through my GoTenna to show mine is being useful and not just sitting there?

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#13

@Kaf2321 you don’t. If you watch it you can see the light when it is relaying messages. But AFAIK there are no counters on how many times you’ve relayed. It is a numbers game. We need more people out there with mesh to get more hops available and better end to end connectivity.

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#14

aspexin is correct. Look for the flashing lights. In fact, look for them on your personal goTenna Mesh, because if you’re near your relay, you will see the LEDs on it flash 3 times when the node relays nearby. When you’re not sending or receiving a message, paired nodes also relay whatever they pickup unless it’s the 6th hop already.

Another thing to do is to post your relay on the node map at https://imeshyou.gotenna.com/ . Not everyone does, but the more people are aware of what others may be doing, the more the mesh gets used.

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#15

Thanks for your reply - I hope you find this information helpful, and that you decide to set up some stationary relay nodes of your own. :smile:

Don’t hesitate to ask for advice from the folks in this community if you have any questions. We’re here to help.

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#16

It would be really helpful to have a setting for the Mesh node to automatically power it back up in relay mode when power is restored, particularly since there is no way for a normal user to determine whether the node is running without physically pressing the button. That the node stays powered off after power is restored after a battery discharge makes it less appealing to place nodes in hard-to-reach-but-rf-favorable places with intermittent power sources.

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#17

Your concern is shared by goTenna and those of us who operate relay nodes. At one point it was hoped this functionality could be effected by a firmware update, but it was eventually concluded it could only be done with a hardware change in the device itself. I hope this change becomes effective soon, but this will require a slight redesign in production to accommodate a new switch.

Right now my 8 nodes are sitting under a diminishing layer of snow that is supposed to be replenished on Saturday. I’m looking at some work once conditions to climb improve, I suspect.

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#18

+1 to that, Mike – I would LOVE to see a product improvement released that permits a goTenna Mesh to power itself back on in relay mode once power is restored. Even if I have to purchase new goTenna Mesh units to get this capability for my stationary relay nodes, I would do it to improve the tenacity of my solar-powered relay nodes. Seeing the volume of posts asking for this across many past topics, it appears that many others feel the same way.

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#19

You got that right. Lots of us want this. I too will invest in new hardware if I have to. I had to move my nodes I had out of the attic as I developed a bum knee and climbing up to replace the battery packs when they eventually die (solar power during winter only bought me about 14 days of juice) is no fun. The nodes are on the 2nd floor but they lost about 12’ of height with the move.

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#20

Can you communicate with others on the stationary relay node? I set on up a couple months ago, it’s always on, using both electrical outlet, and an anker battery and solar panel, and nobody every responds when I shout to the public channel… super bummer