Basic Homelab running on low power NUC

 Generally speaking a Homelab is a personal, non-commercial environment where individuals can set up, experiment with, and manage their own IT infrastructure. This can include a variety of hardware and software components, such as servers, networking equipment, virtualization platforms, storage systems, and more. However most people only need to host a few services such as home automation, personal websites, media servers or backup and storage.

There are plenty of videos on YouTube where users are showcasing their homelab setup, some of which are pretty advanced setups with rack-mounted servers and professional-grade networking gear. In fact, most users will never need all these and when you start a homelab you begin with a list of services you want to host.

A proper enclosure for CNC3018 Offline Controller

I like to have an offline controller for my CNC3018 machine because I want to keep my computer away from the CNC during usage. There is a lot of dust and cut material scraps which shouldn't get into fans and electronics. Speaking of electronics, the offline controller of CNC3018 is just a bare PCB stacked between two nicely machined acrylic plates. There is absolutely no dust protection. Here is issue #1. The next one is that this controller hangs around the CNC. There is no way to attach it to the frame. And the third issue one will encounter when using the offline controller is the loss of computer communication. That is right. If the offline controller is plugged in, you cannot connect to CNC via USB. Basically, both USB interface and offline controller share the only available serial port of the ATmega328p based mainboard.

I decided to fix all these issues. Following is a 3D printable enclosure which can be attached to the side of the frame on existing screws. And regarding the serial port issue, there is an optional cable connection mod you can do. Below is the result.

CNC3018 Offline controler attached to frame side

PID control for DC motor with optical encoder

In the previous post I gathered information about a cartridge slide unit taken from an old inkjet printer. As I found out, the printer used a common DC motor to move the cartridges on X axis, however with the addition of an optical encoder with strip, the cartridges could perform precise movements. So, I want to interface this to Arduino. Original printer electronics such as motor drivers were of no use (proprietary ICs without public datasheets).

I had to drive the motor with a L298N H-bridge module and for the encoder I built a PCB which replaced the original one used in printer. The software is not as simple as you may think. I just can't turn on motor until the reading of encoder equals the desired position. Suddenly stopping the motor will not result in a sudden stop of the sliding block. Due to inertia, it continues to move a bit, even with the motor electrically shorted. The proper approach requires a PID (proportional-integral-derivative) control algorithm which adjusts motor speed using PWM.

The motor with optical encoder wired to Arduino

Optical encoder motor control for printer slide unit

I disassembled an old inkjet printer without working cartridges. Buying replacement ink cartridges was not worth because the price of both black and white and color ink cartridges equals the price of a new printer. I couldn't throw away the printer without taking any usable electronic and mechanic parts from it. To my surprise, the cartridge holder is placed on a metallic sliding unit that seemed interesting.

Cheap design though. Plastic block sliding on metal axis, but since it did its job in the printer, it may work elsewhere too. However, instead of using a stepper motor to control the sliding unit, the manufacturer has chosen a closed loop system with a regular DC motor and an optical encoder with a strip. That's the approach for most home-use printers. When looking for a way to control such a system with Arduino I didn't quite found something that worked.

The printer slide unit with a custom encoder PCB

Fixing a broken rotor coil of 775 motor

I powered a 775 motor and strange things happened. The motor was new, never used before. In less than 10 seconds while it was supplied with voltage, it looked as if something was attempting to block the axis from spinning, I heard crackling noise from the motor then smelled some smoke. Not good... yet it was still spinning. It's worth mentioning the context in which this happened. I was testing a power supply I'm building, and because something went bad the 12 V motor received 30 V with plenty of current (about 7 A). I would expect it to fail under these circumstances, but not in this way and not as fast. Overheated rotor coils and short-circuited windings is what should have happened.

Yet the motor was completely cold and still spinning when I powered it again (this time from 12 V). A short piece of copper wire came out of it - something bad has happened inside. So, I ended up with a partially broken motor. The next thing I did was to open up the case.

775 motor case opened

Chucks for mini drill tools

Miniature drill tools are a must have for everyone who is making his own printed circuit boards (PCB) at home. Not limited to this, drill tools have many uses as rotary tools. Although the motors you will use for DIY tools have smaller power than a Dremel tool, some of the accessories can be used for small work. You can attach cutting discs, sanding, grinding, carving and polishing attachments. What works and what doesn’t depends on the motor you use, the type of drill chuck and the material you are using it on.

Building your own miniature rotary tool is usually cheaper than buying a Dremel tool. If you want something for PCB drilling only, the motor can be very small. And small motors are found in a lot of devices (do not expect to use a motor from a CD/DVD drive for this purpose, but motors from toys, old cassette players, hair dryers, printers, scanners etc. can drill a hole through a PCB). If you are lucky enough to have a motor from battery operated vacuum cleaner or drill machine (like the 775 motor), you can build something very powerful.

Transmission line baluns for VHF and UHF

A balun is a device that converts a balanced signal to an unbalanced signal. Depending on construction, a balun may transform impedance too and may be used for connecting signal lines of different impedances. In radio applications, baluns are used most of the time for adapting a transmission line to the antenna. This post will show you some easy to build baluns, designed for receiving antennas working in VHF and UHF radio and television bands. However, these baluns can be also used for transmitting antennas. They are easy to build because you only use cables similar to the antenna feeder cable.

Most used antenna class for all radio communications is the dipole. Since it's called a dipole, it has two connection points. Therefore it is suited for balanced signals. The antenna can be connected to a receiver using a twin lead cable. But in this case the receiver must have balanced input and similar impedance with the antenna. But the most used type of cable is the coaxial type, which is unbalanced and has a different impedance too. Let's see what are the basic types of connections between the antenna and the feeder cable.

Homemade PCB with toner transfer method

The toner transfer method is a cheap and easy way to make your own printed circuit boards (PCBs) at home. A laser printer is used to print the design on paper. Not all paper types are suitable for this kind of usage. The paper is placed with the printed side over the copper side of the circuit board and then the whole thing is heated. Most people use with good results a common iron, but if you have a laminator, use it instead of the iron. When heated, toner melts and sticks to the surfaces. The idea is to make it stick to the copper layer. After heating, the board is submerged in water and the paper should be easily peeled off from the copper side. A good transfer means no toner remains on the paper. Once this is done, the board can be etched using whatever method you want (ferric chloride for example).

This method is widespread among hobbyists because is cheap and easy. However, for some, the results are unsatisfactory and variable. I will share some of my experiences with this method.

Homemade PCB with silkscreen

Heatsink for RTL-SDR dongle

Some of the popular RTL2832U based DVB-T dongles that can be used as SDR tend to heat too much. As temperature increases, frequency drifts and sensitivity drops. Some dongles, especially those using R820T may stop working at all at high temperatures.

Marko Cebokli (S57UUU) used a thermal camera to measure the temperature of the dongle. He measured up to 85°C at the tuner chip (R820T). His images prove also that the dongle PCB doesn't do a good job at dissipating heat.

Although I'm using a R820T2 dongle (which is said to heat less than the predecessor R820T), I was surprised to see that after only 10-15 minutes the dongle was hot. Opening it up, I discovered that all ICs were hot (the tuner R820T2, the RTL2832U, the 1117 regulator, even the EEPROM was heated inside the closed case of the dongle).

How to align satellite dish

After some unsuccessful tries to align a satellite dish do you think it's rocket science? Well, the calculations are difficult but the practical thing isn't. Despite what many believe, it is easy to align a satellite dish as long as you know the parameters than can easily be calculated online these days. Of course you are looking towards the sky, but you must be looking towards the satellite. This is not the usual practical guide to satellite dish installation. For that there are plenty of resources and video clips on YouTube. I'm gonna explain all the steps required to successfully receive signal from a satellite and explain why you do that and that. Everything from mounting the dish, connecting the LNB and receiver and looking for signal on the right frequency.

Make a wideband antenna matching transformer

Most do-it-yourself TV antenna projects I could find use a readymade impedance matching transformer between antenna and cable. But what should you do if you can't find one at your local supplier? Let's attempt to make one with nothing more than some copper wire and a ferrite core. You could use some hard to find double hole pig-nose RF ferrite cores, but this transformer performed fairly good with ordinary toroidal cores.

This matching transformer can be used for VHF and UHF reception (from 50 to about 800 MHz). The input is 300 ohms balanced and the output is 75 ohms unbalanced, ready for coaxial cable connection. I found out that a device similar to what is presented here is used in commercially available antenna preamplifiers with 300 ohms input.

Make a multifeed LNB bracket for your satellite dish

Although a satellite dish is designed to receive signal coming from a single direction, by placing additional LNBs near the main one you will be able to receive more than one orbital position. Thus, each LNB will receive signal from a different satellite. You can receive in this way signal from satellites placed at near orbital positions. Having multiple LNBs fitted to a dish is called multifeed and it comes with advantages and disadvantages. The main advantage over a motorized dish is the fact that it is a fixed installation and you can change channels instantly without waiting for the antenna to move. However, the additional LNBs that are not placed in the middle focal point will receive lower quality signal than the main one.

Brackets for multiple LNBs are commercially available, but I found them rather... rigid. Most of them are for 2 or 4 LNBs and don't allow too much fiddling to get the best signal quality. Let's try to make that bracket. It must keep a constant focal distance and should follow the inverted reflection of Clarke orbit. The focal distance depends on antenna and orbit reflection depends on dish size, receiving location and satellite positions. The distance between LNBs is proportional with dish diameter. You will learn how these parameters affect the LNB bracket shape and size and how you can calculate distance between LNBs.

Photo courtesy of Paul Lucas on Flickr

Connect multiple satellite receivers to a single LNB

A TV satellite receiving installation is usually made up of a dish, LNB and receiver. A single LNB is designed to feed one receiver. Yet in some circumstances, depending on received transponders properties, a LNB with a single output can feed multiple receivers, although the number of received transponders will lower. The best solution is a multiple output LNB.

Gray-Hoverman, the wideband TV antenna

In the past, air TV channels were broadcast on frequencies ranging from 170 MHz to 860 MHz. The VHF-Hi band covers 175 to 230 MHz, while UHF covers 470 to 860 MHz. This is a large interval, covering two bands and it is difficult to receive with a single antenna. But, nowadays the UHF band for TV broadcasts is getting smaller. Frequencies starting from 600 MHz are being repacked for mobile networks.

The Gray-Hoverman antenna has been designed by Doyt R. Hoverman and it was patented in the sixties. It only covered the lower part of UHF, from 470 to 720 MHz (21 - 52 channels). If that could have been a problem, it's not anymore. The average gain in this frequency range is 13 dBi with reflector and 9.2 dBi without it. With some additional elements, this antenna can also receive the upper part of VHF from 170 to 230 MHz, with an average gain of 8.1 dBi with reflector and 6 dBi without it. The overall gain is not too much but, since it is easy to build and wideband it's worth a try. The original design has been republished and distributed according to the GNU GPL version 3 license.