Dish antenna for the amateur radioastronomy

In the previous article I discribe low noise amplifier for the 21cm band. Today I wanna show you construction of the dish antenna where this amplifier can be used.

Continue reading “Dish antenna for the amateur radioastronomy”

Low noise and low cost amplifier for radio astronomy, 21 cm band.

21 cm band also known as Hydrogen line is one of the important bands in radio astronomy.

Please read this wikipedia article if you not familiar with Hydrogen line.

Nowadays even radio amateurs can observe this signal from the outer space, thanks to modern hardware.

One of the most important part of the any receiver is antenna and input stage. Typically input stage is some kind of the amplifier with extremely low noise and high gain due to weakness of the space signals.
In this article I want to describe simple and cheap amplifier for the first stage of the receiver.

Continue reading “Low noise and low cost amplifier for radio astronomy, 21 cm band.”

Powerful DC motor driver using IR2110

To control speed and rotation direction of the DC motor we need some type of the motor driver, one of the most popular schematic is H-Bridge. For the low current and voltages we can use some integral solution like L293D and so on. But if we need more power and reliability we have to build some custom H-bridge using mosfet transistors. This type of the transistors requires careful and proper driving itself. One of the most popular integral solution for driving mosfets is IR2110 from Infineon.
In this article we will discuss how to use this IC to build powerful DC motor driver.

Continue reading “Powerful DC motor driver using IR2110”

Autonomous Allsky camera with Raspberry PI. Part 3: shooting night sky in FITS using QHY5-IIM camera

This is a third part of the Allsky cycle.

Please read previous articles to get complete information about this project:

Part 1. Autonomous Allsky camera with Raspberry PI: overview.
Part 2. Autonomous Allsky camera with Raspberry PI: powering and lightning protection

This time I will show my utility and script for shooting night sky and processing of the images.

Continue reading “Autonomous Allsky camera with Raspberry PI. Part 3: shooting night sky in FITS using QHY5-IIM camera”

Isolated USB to RS485 adapter

RS485 is a standard for use in serial communications systems. Electrical signaling is balanced, and multipoint systems are supported. This communication standard is used in a wide range of computer and automation systems. RS-485 is used as the physical layer underlying many standard and proprietary automation protocols used to implement Industrial Control Systems, including the most common versions of Modbus and Profibus, also used in building automation as the simple bus wiring and long cable length is ideal for joining remote devices. It may be used to control video surveillance systems or to interconnect security control panels and devices such as access control card readers.

In this article I will show how to build simple and reliable USB to RS485 adapter with galvanic isolation and ESD protection.

Take a look at the second version of this adapter.

Continue reading “Isolated USB to RS485 adapter”

Autonomous Allsky camera with Raspberry PI. Part 2: powering and lightning protection

This is a second part of the Allsky cycle and I want to describe powering and protection of this device.

Please read first part to get basic information about this project.

Continue reading “Autonomous Allsky camera with Raspberry PI. Part 2: powering and lightning protection”

Autonomous Allsky camera with Raspberry PI. Part 1: overview.

Allsky (or weather) camera is one of the most important part of the modern observatory.
It’s very important to monitor sky condition during night observations, especially when observatory is remote controlled or should be fully automatic. Different vendors provides different solution. But all they are share the same problems: very high prices, lack of autonomy (PC is required) and lack of useful sensors like a temperature, sky temperature and so on. So, to build complete system you need: camera itself, PC, weather station, cloud sensor. Full price and complexity of this system is very high.
But this not a Jedi path, right?
With this article I’m starting the cycle of the materials dedicated to fully autonomous device, based on Raspberry PI. This device contains two cameras and a lot of sensors.

Continue reading “Autonomous Allsky camera with Raspberry PI. Part 1: overview.”

Connecting HTU21D temperature/humidity sensor to the Raspberry PI using simple C i2c interface

Previously in my projects I’m always used well known DHT22 (AM2302) temperature/humidity sensors. But I found that this sensors is not very stable and subject to hungs. In my case this device is worked about two weeks and then stops responding untill power rebooted. This is absolutely unacceptable on some distant and autonomous devices. After some googling I found that I’m not alone and some peoples also expirienced such problem.
I’ve decided to replace this sensors to something more reliable and more accurate. My choice fell on HTU21D from the Measurement Specialties. HTU21D is a quite reliable and precise sensor, much newer than DHT and uses standard i2c bus instead own 1-wire protocol. I2C interface was a determinative and in this article I want to describe connection of this device to the Raspberry PI in details.

Continue reading “Connecting HTU21D temperature/humidity sensor to the Raspberry PI using simple C i2c interface”

Isolated eqmod adapter for the telescope control

There are popular and quite cheap amateur telescope mounts from different vendors: Sky-Watcher, Celestron and so on.
Most of that mounts contains motors and some controller schematic. User can control this devices in different ways. One way is to use mount’s handcontroller, other way is connect to computer and use some software to control and guide the telescope. Such connection can be made through special adapters (often called eqmod). Technically this adapter is just some kind ot serial converter, RS232 to UART (TTL) or USB to UART.
Here I’m describing a very reliable and simple adapter with galvanic isolation that I was developed and made.

Continue reading “Isolated eqmod adapter for the telescope control”