Automatic monitor brightness controller


Dilshan Jayakody writes:

This is an automatic “monitor brightness controller” based on environmental light conditions. This system use USB port base sensor unit to measure the light level and control monitor brightness accordingly. We design this system to reduce the eye stress by matching the monitor brightness with environmental lighting.

Project info at Dilshan Jayakody’s blog.

A 1-meter-diameter small transmitting loop for 7 MHz, part 1


qrp-gaijin has been working on a 1-meter-diameter small transmitting loop for 7 MHz:

I’ve decided to try constructing a smaller, more traditional loop of 1-meter diameter. A smaller loop means smaller radiation resistance, and that means that small values of loss resistance become more significant. Great care must be taken in all aspects of construction to minimize the loss resistances.
This series of articles will detail the progress of the project.

Project info at qrp-gaijin blog.

Mains 230VAC isolator


Jaanus Kalde has built an isolator box:

Probing mains powered schematics is hard. Most oscilloscopes are earth referenced, so connecting ground probe to random spot of mains connected device will make a small explosion. Also there is the risk of electric shock by touching wrong part of the schematic while being in contact with something grounded like a desktop computer case
To combat these dangers I built an isolator box. I took an 1:1 transformer rated for 230 VAC 50 Hz mains voltage used in Europe. With 0.76 A current output capability it gives me ~170 W to play with. To make it even more useful I added a second output that goes through a diode bridge and has bunch of filter capacitors. This gives me rectified DC voltage to use, since most schematics rectify it anyway.

Project info at Jaanus’ blog.

Building a simple circuit probe

Probe 4

Vicente Jiménez has published a new build:

Sometimes you need to check one circuit and test some of its nodes. Usually a tester in voltage mode is a good solution, but it has a pair of problems. First, it measures about zero both when the node is driven at zero volts and when the node is floating (not driven at all). Second, it gives the information on the tester display, so you need to take the view from the circuit to the tester to check the voltage.
The proposed circuit somewhat qualifies as a logic probe. It should give no indication when the node is not being driven and it should give a different indication when the node is driven at high or a low voltage.
A lot of logic probes are not self powered. They rely on the circuit supply to operate. In my case I would like the probe to be usable also a as a continuity tester. If we set ground in one point of the circuit and we probe another point, the continuity can be detected between both points because a low level will be driven even if the circuit is not powered at all.

More details at r6500 blog.

(Nothing less than) The perfect tea timer


Michael from Acidbourbon has built the “perfect” tea timer project.  He wrote a post on his blog detailing its assembly:

Maybe you just drink coffee. Then this article is not particularly interesting for you. But if you like a cup of black or green tea once in a while you might know the problem: You prepare your tea and you let it stand for a minute too long. Then it is bitter. So the next time you use the timer functionality of your smartphone … unlock the screen, open the timer app, enter something like “3:00″ (minutes), press start, pour boiling water over the tea, wait. Then your phone beeps like crazy while you are fumbling around with the hot and wet teabag you want to dispose of. Finally you unlock your beeping phone with your wet fingers, open the timer app again and silence it. Pure stress.
Of course that is a first world problem and you could just deal with it. Or if you are a tinkerer, like me, you might want to build yourself the perfect tea timer. The desired properties are:

Very small
Extremely simple user interface
When finished it plays a short melody and goes to standby by itself
Not expensive
Long battery life

Project info at Acidbourbon site.

Check out the video after the break.

A DIY wearable posture sensor


Want to improve your posture? This wearable posture sensor from Coretech Robotics will remind you whenever you slouch and help you maintain a good posture:

Posture sensors/monitors have been a recurring theme on this blog. They are supposed to remind you of your posture and prevent you from slouching, which can be a cause for back pain and headaches.While my previous sensors were either fixed to a chair or desk, this time I wanted to create a wearable version, that would allow for free movement. As always, one of the main goals was to make this project cheap and easy to reproduce.

Project info at Coretech Robotics site.

PWM dimmer for RGB LED


Lukas Fassler has designed and built a PWM dimmer for RGB LED:

In my last post I’ve described the design and construction of my LED dimmer project. This project here is similar but a bit more involved. It controls RGB LEDs so it can not only change the brightness but also the color of the light. Instead of a simple pot it used a pair of rotary encoders with push buttons. One controls the brightness, pushing its button turns the light on or off. The other changes the color, pushing its button toggles between color and white.

Project info at Soldernerd site.


Music Thing Modular Axoloti control board


Tom Whitwell from Music Thing Modular built a DIY control board for Axoloti, that is available on Github:

Axoloti is a very nice €65 audio board from Belgium, the closest thing I’ve yet seen to an Audio Arduino; lots of easy analog ins and outs for pots and switches, enough power to do interesting audio, and a nice visual patching system. A bit like a Nord Modular for 2016.
I’ve put together a simple control surface for my Axoloti; pots, buttons, LEDs and a joystick.

Project info at Music Thing Modular site.

Check out the video after the break.

Instruments for the GSXR


Josh from imsolidstate made a new dash panel for his streetfighter based on an ATmega128, a Planar EL 160×80 display, and an Epson S1D13700 controller:

Since the GSXR is now a street fighter the factory gauges won’t do, and I wanted something I could log air/fuel ratios with so I can jet the bike. I went a little overboard making a new dash.
I had a Planar 160×80 EL graphic display that’s been in my parts bin for years that I’ve always wanted to use, and this was perfect. Unfortunately it doesn’t have a controller so I had to interface it to the CPU with an Epson S1D13700 graphic controller. The display indicates speed from a GPS module, air/fuel ratios from the wideband O2 sensor, engine temp, battery voltage, time from GPS, and RPM. I used a light sensor to sense ambient brightness levels and dim the display by changing TC/R in the graphics controller. The refresh of the display is high enough to allow a large dimming range without flickering. The EL display can be refreshed at up to 240Hz.

Project info at

Check out the video after the break.

Mullard 3-3 Amplifier project (part 2)


Dilshan Jayakody writes:

This is a second article related to Mullard 3-3 Amplifier Project and in this article we introduce HT transformer and HT power supply related to this amplifier. As mentioned in previous post, power supply unit of this tube amplifier is constructed using 400V 5A bridge rectifier, 220µF (400V) and 82µF (400V) electrolytic capacitors.
The most vital component of this power supply is HT transformer and due to limited availability we construct this transformer by ourselves.

More details at Dilshan Jayakody’s blog.