Simple obstacle avoidance sensor for free-running robots
Free-running robo-car must has some obstacle sensor to avoid hitting walls. I've described ultrasonic distance sensor that can measure the distance to an obstacle, but there are simpler sensors that use infrared LEDs. They can't measure the distance but they can indicate that the distance is short. Those are so called obstacle avoidance sensors. They can be used in robots to avoid hitting obstacles or as sensor indicating for example if the doors are open or closed.
Using analog joystick boards to control components of electronic circuits
To control robots, or some electronic values we often need some potentiometers. One potentiometer is just one value. To make things easier for controlling multiple parameters at once joystick were invented. Nowadays you can get cheap "analog" joystick for your microcontroller that allows you to control signal from two axis - X and Y. That can be used for example to control where and how fast a robot-car is going. Such joystick has two potentiometers moving in perpendicular axis.
In this article I'll cover the basic 5-pin joystick boards. There are also Arduino shields or more advanced joystick boards that may have more pins and more features.
Controlling servo and stepper motors with pyMCU
Servomechanism, or a servo for short can be found in RC car models where they can turn the wheels or flip ailerons in RC planes. They can also move mechanical arms and grippers. Making it simple a servo is a motor with some gears and electronic controller that knows the current motor position and can set it to any requested from the supported range. Simple servo can move only in some range, like 180 degrees, but there are also continuous servos. With a big bunch of servos you can create a hexapod - mechanical spider.
Stepper motors can be handy in devices that require very precise movement (like CNC machines). The motor moves in steps and each step is triggered by a electronic pulse. You can precisely control by how many steps the motor will move.
Controlling DC motors with pyMCU and DRV8833 motor controller
DC motors can be found in many devices. In do-it-yourself projects they can be used to create robots like "smart" cars driving around and avoiding obstacles. Such motor can be turned on and off, and we don't get any control of the rotation speed or direction. To control such motors some controllers were designed. They take a shape of integrated circuit containing H bridges. You can find multiple driver boards on the market. They differ in the amount of supported motors, or their power. More powerful motors using more amps will require better, more expensive motor controllers. For cheap robot-sets for Arduino and alike you can usually use the weaker and cheaper controllers, or also boards that integrate motor controllers with other robotic features (some Arduino shields, RaspiRobot, Rover 5 etc.).
In this article I'll showcase Pololu DRV8833 dual motor driver controlled with pyMCU microcontroller. It one of cheaper drivers intended to use with weaker motors - just like those in small robots. Other motor controllers should work in very similar like if not identical way.
Configuring various browsers for Selenium web applications tests
Selenium can test your web applications quite easily (at least the frontend). To perform the tests it launches a webdriver which in most cases will be Firefox. But what about other browsers that may interpret CSS/JS differently, or what about mobile browsers on mobile devices? Selenium does support them, but to get them working some extra configuration is required. In this article I'll show how to make other browsers work with Python Selenium client (on Linux).
Cooling e2v EV76C661 sensor
I reviewed IDS Imaging UI-1240ML-NIR-GL camera equipped with EV76C661 sensor. When using high gain and longer exposures around 30 ms for Saturn dimmer channels the noise - hot pixels were quite apparent. On rolling shutter the noise (at least read noise) should be low. So most of the visible noise should come from dark current. To check that I've cooled the camera using a fridge to few deg below zero. Below you can see how the noise lowered when the camera cooled from ambient 20C to around 0C (39.46ms exposure, gain 355 - max).
A Peltier cooled camera would be very desirable. It would allow easy Neptune and Uranus imaging at much longer exposures (or Jupiter methane band) without overwhelming noise. Saturn would like that too. Plus maybe some DS imaging if it would handle ~5 min exposures at low noise.
As global shutter gives a lot of noise even when cooled we can look at EV76C660 which works only with rolling shutter and offers on the paper even higher sensitivity and only ~3e read noise. However those sensors aren't available in machine vision cameras - either due to rolling shutter or they are just unavailable on the market. I would really wan to see a cooled camera with such sensor. Even for planetary imaging the shutter isn't perfect but it seems to work if the conditions aren't bad.
Review of IDS Imaging UI-1240ML-NIR-GL camera
IDS Imaging UI-1240ML-NIR-GL is a camera that I use from some time now. It's equipped with one of newest CMOS sensors - e2v EV76C661. In the past I tested cameras with the previous generation of e2v CMOS sensors - IDS cameras, as well as Ximea. New generation promises higher sensitivity. Is that true I'll try to answer in my review.
Schiefspiegler - a tilted mirror telescope with no obstruction
Schiefspiegler is probably the most popular of tilted telescope designs (TCT). It consists of two mirrors but the secondary is moved aside so that it doesn't shadow the primary mirror. Both mirrors are tilted for the design to work. Such design gives no obstruction - which is very handy for planetary imaging or observing. Schiefspiegler were initially made in Germany, and now they are sometimes made by amateurs.
If you would want to get a complete set of mirrors for such telescope then you can visit Vistara website. You can get a mirrors set with 108 mm primary. You also get optics report and instruction on how to build a telescope with such optics. Somewhat bigger sets should also be possible.
Schiefspiegler by Vistara may even look like so:
The primary mirror is in the mount base while in the funky nose we have the secondary.
Combining RFID, NFC and QRCodes with django-oscar online shop
You can write a lot of tutorials about making web apps. So to make something different lets talk about using some hardware and combine it with a shop. I'll show how to use RFID, NFC and QRCodes with a django-oscar based shop.
RFID is close range radio communication. It can be used in many places like in logistics to track packages, or for identification cards. You need a RFID reader and a RFID tag with the radio device. The tag may be a sticker, a clip or something else (a lot of shape and sizes). The the tag is put close to the reader the electromagnetic field induces current in the tag that powers the radio devices. It sends back data to the reader. In most simple RFID standards it will be just unique identification number. In writable tags it may be an URL pointing to the product on the website.
Using Arduino sensor boards with pyMCU
There is a lot of boards that can be used with Arduino. There always will be something new to test and use. In this article I'll present three boards working with pyMCU - buzzer, ultrasonic distance sensor and an alcohol sensor.
