After reviewing the Rak Wireless miner in a previous blog post, after receiving my own Nebra miner, I’ll give a review of it.

The Nebra miner is one of the different Helium miner machine. It is at first a LongFi (LoRaWan) gateway. It includes a software to run it over a blockchain to create a global IoT network. you can get more details on what is helium in the linked blog post.

This review is on a Nebra batch #1, it is possible that some of the given information will not be valid in a couple of weeks when the batch #2, #3 … will be delivered. No need to precise it but this is an end-user review. I’ve ordered and paid my miner. I’ve no link with Nebra.

Let’s see what is in the box !

Inside the Nebra box, a pretty nice package, you have the Nebra miner, the power supply with all the connectors for using it anywhere in the world (but this is a 868Mhz version) ; the radio antenna, a network cable and 2 stickers !

It’s a really good choice to add a network cable as not all the miners have one and it is frustrating to be stuck because of it. The WiFi is not the recommended solution for connectivity so it is better to have the cable coming in the package.

The Nebra miner is a plastic box, a bit big compared to the RAK miner but nothing problematic. It’s correctly finished from the outside, the big Nebra brand on it. I like it !

The Batch #1 has some problem in the inside, I’m quite sure they will be fixed really quickly. But you need to make sure your antenna connector is correctly screwed or you will have to open the box and screw it correctly. This is an easy thing to do. Some miner has larger assembly problem according to the social network but nothing you can’t arrange on your own.

Let’s open the Nebra box

You don’t really need to open it (once the radio connector is correctly screwed) so, I did it for you to see what it inside.

You can see the Nebra mother board in the center, this one has a large connector for the Raspberry Pi handler on the back. The Nebra motherboard has also the LoRaWan concentrator connector. 2 USB connectors on the left and the secure element on the right. You have the Ethernet connector and Radio connector on the front side. There are 2 leds and the power connector also.

The 2 USB connectors are used for the WiFi connectivity and the BLE connectivity. As a consequence the WiFi performance will not be really good. Compared to the RAK miner where the metallic box was a problem, here, we have a plastic box but a really low quality WiFi antenna in the dongle located inside the box. So It is really better to use it with the Ethernet cable. For an indoor usage with the WiFi access point located 5 meters around, this is not a problem.

On the top right, you can see the raspberry PI. It is a compute module 3 with 1 GB of RAM and 32GB of Flash. There is no SD CARD so the miner run on the CM3 internal Flash. This is good as this flash is fast and reliable but in case of problem all the CM3 will have to be changed. This will be more difficult than getting a new SDCARD.

As you can see the Compute Module 3 just have a tiny heatsink on the top. There is no air flow or use of the enclosure to dissipate temperature. As a consequence the CPU temperature will be about 69°C in normal use, with an indoor standard temperature around 20°C.

The CM3 is stable (not like RPI4) so this should not be a problem. Personally I’m running some CM3 with such heatsink for a while and they are good up to now.

That say, you need to be careful if you use this miner in an outdoor enclosure or under a roof during summer.

The more surprising parts inside this miner is the large duct tape on the CM3 and the Motherboard. We could imagine they used it to attach the components as nothing is really retaining the CM3 adaptation board attached to the motherboard (this is a bit surprising btw). In fact these duct tape pieces does not retain anything.

I assume they have been added to pass the CE / FCC certification. They are protecting against electromagnetic some part of the circuit including the power stage on the motherboard and the I/O board (potentially power also) on the CM3 adaptation board.

This is a particular way to solve such issue but I assume it was the fastest way to do this. As a miner I’m really happy they found a such solution instead of making a new revision of the board with more standard shielded enclosure or rebuilt circuitry. Quick and dirty somehow, what is important today is to quickly get the miners.

You can’t miss the secure element on the board. The way it has been soldered is also quick and dirty. Seeing this, I immediately through about unsoldering it and see how to use it in a DIY ! LoL But right know it’s not the time to investigate such kind of hack:

WHAT WE WANT IS TO START MINING !

Installation

The installation is like for any hotspot, it is made with the helium application. I had some difficulties but they seems to come from the Helium application more than the Nebra Miner. The pairing process with the miner has been complex:

• The pairing button is placed between power supply and antenna so once everything is connected it is a bit complex to access (this is a really little issue)
• The pairing seems not working a second time : during the 2 tries I had to do, pairing process was an immediate success on the first time but then I had to reboot and wait before being able to pair again with the miner.

There are two leds on the front of the miner. The first one (orange) seems to be the power indicator. The second one is unknown. (it may be documented somewhere but when getting the device you don’t know) Sometime it is fixed green, sometime flashing green. So I’m not sure of it.

The Chain synchronization has been quite fast (synced during the night), this is really good.

Operation

Nebra ha deployed a simple but really useful solution to monitor the miners. This is really nice when you have remote miner and you want to monitor them and reboot them. Apparently Nebra is using Balena.Io platform (you can check my blog post about Balena.io here) to monitor and access the miners. So you also get an access to some of the metrics and remote operations.

This is a real plus for the Nebra miner. You need to pay attention that if you shutdown the miner you won’t be able to restart it remotely … The RED button !

The dashboard shows board temperature (Compute module), memory and Flash state. The information about revenue sounds incoherent today but it should be related to the Helium API. To register your miner in this dashboard and access to the information, you need to enter two information printed on the back of the miner and on two separated stickers.

So make sure the miner is not accessible by a third party of these information have been removed or this third party will be able to remotely restart / stop your miner.

You need to enter the RPI serial and the Mac value (this one is set without the “:”) this is to prove your ownership and add the miner to your dashboard.

Return on experience

After 4 months, one of my two Nebra has a problem with the LoRaWAn concentrator, the reason is not clear up-to-now. To fix this quickly I gave a try to a RAK 2247 SPI concentrator and this is working correctly since. So this concentrator sounds compatible.

Conclusion

The Nebra miner, even if the one I received is a batch 1, is correctly finished and ready to be used. I’m not sure how it will be in a year or two mostly due to the temperature inside and the choice of USB extension but for now it’s good to start. I’ll update this post if anything significant comes with the use.