Portable Mesh Node with VOIP and Wifi

The main use for our mesh network is emergency communications. The purpose of having our own data network is that hopefully it will be up and functional when all other services are down like power, phone, Internet, etc. At our main nodes we have battery power and at some sites generators. The meeting points during emergencies are at the 4 LDS church buildings in out district. Due to church policy we can’t permanently install any equipment at church building. So we need a temporary and portable setup that can be quickly deployed at the church.

In our community individuals in each unit are assigned to be an Emergency Communications Specialist. This individual is responsible to relay communications from the block captains to the district coordinator, who then will communicate with the city. These individuals may or may not have a HAM license. Right now none of them do in our district. They are soccer moms, retired folks, parents, etc. So we needed a setup that could be used by anyone not familiar with radio equipment or AREDN software.

This setup also needed its own power supply as we can’t expect there to be grid power at the church building. We also need wifi access to the mesh network so they can use a cell phone, tablet, laptop to use Mesh Chat or other IP services on the mesh. We decided to incorporate VOIP with ATA phones since everyone knows how to use a phone.

Described below is the design we came up with and build instructions. The setup has a tripod with a 10′ piece of EMT. A 2.4Ghz 20db patch antenna with a Ubiquiti Bullet M2-HP flashed with AREDN is at the top of the EMT. A 100′ CAT5 able is ran from the bullet to the indoor unit. The indoor unit is a plastic battery box with a marine deep cycle battery inside. Attached on top of the battery case is a project enclosure with a VOIP ATA adapter, wifi access point, battery low voltage cut off, and 3 voltage regulators.

The battery used will power all the node components for about 5 full days. The battery charger selected is perfect for the job since it will power the load when it is float charging keeping the battery voltage at 13.1v during the float cycle. Fancier battery chargers will rotate between float and bulk with this load on it. That is ok but will wear out your battery faster.

Here is a pic of a finished unit:

Here is what the outside tripod with antenna looks like:

Below is a block diagram of how things are connected together. The bullet connects to the mesh network and is connected to the indoor unit with a 100′ CAT5 cable. That cable plugs into the top of the indoor unit in a CAT5 wall plug. That RJ45 is connected to a POE injector that is attached to a voltage regulator. The bullet will handle 24v down to 10.5v. Optimally it is best to run it around 12v. We have a 100′ cable the voltage is going over so we set the regulator to 15v and after the 100′ cable that ends up being around 14v to the radio. With a 300′ cable the drop is to 12v. So we can use either length just fine with a 15v input. You can play with numbers with this online POE calculator. The data part of the CAT5 plugs into the VOIP ATA adapter. This has 2 RJ45 ports and has been configured in bridge mode. The second port of the VOIP ATA adapter plugs into the wifi access point. The VOIP ATA adapter needs 12v. Our battery will supply as high as 14.6v while being charged, and down to 11.0v when the low voltage cutoff will disconnect. 11.0v is a good point to stop the draw on the battery to preserve its life and not ruin it. So we have a step up and step down regulator that will supply it 12v when the input voltage is higher or lower than 12v. We also have a 5v regulator that supplies the wifi access point and a USB light.

Here is a block diagram of all the components connected together.

Ok now that you have a good idea on why we built this and what it does, here are instructions on building one yourself. Here is a component list. I buy everything I can from Amazon since I have Amazon prime and it would take forever to try to find all this stuff locally, and it just shows up at my door :). The whole setup will cost you around $500 – $700 depending on what stuff you already have.

Component	Notes
POE Injector	Combines Ethernet + 15v from the voltage regulator.
2 x ATA Phones	These phones have a backlight which is nice. Any ATA phone will do.
VOIP ATA Adapter	Connected the phones to the mesh. Need to have 2 RJ45 ports. Once for the radio and one for the access point.
Step Up Converter	Takes out 11-14v from the battery and steps it up to 15v for POE to the Ubiquiti radio.
Wifi Access Point	Gives wifi access to the mesh network.
Step Up / Down Converter	Setups up or down the battery voltage to a constant 12v for the VOIP ATA Adapter.
Project Box	Box to put all our parts in. Does not need to be this exact size.
Voltage + Current Display	Shows the battery voltage so we know how much juice is left, and how much current we are using.
Power Switch	So we can turn it on and off.
5v Converter	5v converter for the wifi access point and USB light.
Low Voltage Cut Off	This cuts off the battery when it gets too low. If you drain it too low it will ruin it.
USB Light	If there is no power you are probably going to want this.
USB Keystone	USB jack from the wall plate to put the USB light in.
RJ11 Keystones	Outlets for the ATA phones.
RJ11 Keystones	Wall plate to hold the keystones.
RJ11 Keystones	RJ45 keystone for POE to the radio.
100' Ethernet Cable	Patch cable to attach the indoor unit to the radio.
Ubiquiti Bullet M2HP	Radio to connect to the mesh. Any AREDN supported radio will work.
Panel Antenna	20 db antenna for our radio.
Tripod	These are actually speaker tripods but work perfect for this. They come in a pair so give one to a friend.
Battery Box	Box to hold out battery and to mount the project box to.
Battery charger	Charges the battery and runs the electronics. Keep this plugged into the battery all the time even when not using the node. The battery requires a trickle charge or it will go dead.
Sand Bags	These hold down the tripod. A $4 / 50lb bag of sand from Home Depot will fill 3 of these.
Battery	122 amp hour deep cycle battery. Make sure you get a deep cycle battery. If you use a regular car battery it will ruin it quick. This will run the node for 5 days.
1" 10' EMT	This fits nicely into the tripod stand. Your radio will be about 12' off the ground. You can use a telescoping pole if you need more height.
USB Connectors	USB solder on connectors to plug into the regulator and USB keystone.
Solder	Solder to connect all the wires and plugs.
Terminal Plugs	These attach to the power switch.
20 Gauge Wire	For all the internal wiring in the project box.
Heat Shrink	These protect the solder joints. Use a heat gun to shrink in on.
Ring Terminal	Ring terminals to connect to the battery.
14 Guage Wire	Connects the battery to the Low Voltage Disconnect and the power switch. Get some black too.
5.5mm x 2.1mm Power Adapters	Wires up the POE injector and the VOIP ATA Adpater.
CAT5 Cable	Ethernet cable to wire the VOIP ATA Adapter to the wifi access point and the POE injector.
RJ45 Connectors	RJ45 connectors for the CAT5 cable.

Tools needed:

Wire strippers
Wire ties
Double sided sticky tape
Soldering iron
Dremel with plastic cutting wheel and bit
Screw driver
Screw gun with drill bits
RJ45 crimp tool
RJ11 crimp tool
Hot glue gun

First step is to configure all the gear. Flash your Ubiquiti radio with AREDN software. The you need to configure the VOIP ATA adapter to connect to your Asterisk server and use bridge mode. Then configure the wifi access point to be in AP mode and change it from using Smart DHCP to have a static IP address.

Now it is time to assemble the indoor unit.

Start with measuring and marking the project enclosure with a pencil with where you want the components to go. For the wall plate you only need to cut a hole big enough for the connectors to drop into the box. Leave enough room to screw the wall plate to the box.

Then mark holes for the voltage display and power switch.

Now drill out the corners of the boxes to make the Dremel cutting easier.

Now use your Dremel with the plastic cutting wheel to cut out the squares. Cut one line at a time and then use a flat head screwdriver to quickly remove the melted plastic from the top. If you don’t do this then you will have to cut it off later when it is dried and that sucks. Don’t use your fingers unless you want to get burned. I did all the cutting in a box to make cleanup easy and keep all the shavings for going all over. Earmuffs and safety glasses are a good idea.

Now everything is cut out you should have something like this:

Yeah I know, my Dremel skills could use some work :). Now try to fit the switch and voltage display. You may need to trim some spots to get it in. Drill some holes for the wall plate too.

Make sure to mount the wall plate with the UP label on the back in the direction you want it. Now screw the plate to the box and you should have something like this:

Now we are going to attach the project box to the battery box. Put the two together where you want them and drill a couple of holes between the two and attach some small bolts and nuts to hold them together. Then drill another hole for the wires to run down to the battery. Use the spots in the pic to prevent any shorts. The low voltage cutoff has solder points on the bottom so you for sure want to avoid a bolt under there.

Use double-sided sticky tape on the studs to mount the components in the box. We will hot glue them in too so don’t worry if they are not super secure right now. Run about 16″ of 14 gauge wire from the low voltage cut off down into the battery box. Connect the wires to the battery IN connection like in the pic. Set the dip switches on the low voltage cutoff to shut off at 11.4v and reconnect at 12.1v.

Now mount the VOIP ATA adapter and the wifi access point.

Now lets set the voltages on the regulators. Hook up a 12v power supply, one came with the VOIP ATA adapter if you need one, and a multimeter to the other side. Then you turn the POT, the tiny screw on the blue box, to adjust the voltage. Set the step up regulator to 15.0v and the step up / step down regulator to 12.0v.

Ok wire everything up using 20 gauge wire. See pic and block diagram for reference. The black wire from the voltage display does not go to anything so put some heat shrink or tape on the end so it does not short anything. Hot glue the components in place so they don’t move around. Use sticky tape to secure the regulators to the box, then hot glue those too. This pic is missing the 5v regulator. See a below pic for placement.

Ok now solder the connections together. A pair of Helping Hands sure helps. Basically you are going to solder up all the reds together and all the blacks together. The blacks will all connect to the yellow wire from the voltage display and the reds to the red wire on the voltage display. Solder the small red wire from the voltage display wires in with the reds too. The small black wire from the voltage display does not connect to anything. Cut off the end and slide a piece or heat shrink on the end. Put some heat shrink on before you solder so you can slide it down over the solder connection and shrink it on. I find it is easiest to twist all the wires together, then solder them together. Then do the same to the other end you will connect, then solder them both together.

Ok now do the USB connections. Solder the connectors to 20 gauge wire, then cut the USB cable that came with the wifi access point and solder it to them other two connectors. Make sure to get the polarity correct like in the pic. Heat shrink on the solder connections.

Now plug that cable into the regulator, wifi access point, and the USB jack in the wall plate. Wire up the RJ45 to the injector and the RJ11’s to the VOIP ATA Adapter. Now everything is connected and should look like this. Make a small patch cable to go from the LAN port of the ATA adapter to the wifi access point.

I connected the battery cables to a 12v power supply to power it up and test the voltages and polarity going to the expensive items to avoid releasing magic smoke :). Now add the connectors to the battery cables.

Now attach the battery cables to the battery, positive side first. Also attach the battery charger plug to the battery then snap the top on. Now you are all assembled and should look like so.