Meter clock: keeping “current” time. Read more about the clock:
I’ve seen a few meter clocks in my travels of the web, and I love the idea. A few days ago, I decided that I must have one of my own. Such began the “How to do it” pondering cycle. I had seen builds where the face plate of the meter is replaced. This works, but I wanted to try and find a way to do it without modifying the meter, if possible. After some more ponderation, I came up with what I think is a serviceable idea.
I came across this style of milliamp meter on Amazon. They’re not quite 0-60 mA, but the 0-100 mA (a 0-20mA meter for the hours) is close enough. And they were cheap. So yay.
Part of my requirements were that the clock run off of an Arduino Pro Mini I had lying around, and with minimal additional parts. In order to drive the meters with some degree of precision, I would use the PWM pins to vary the effective voltage across a resistor in series with the meter. This would, by the grace of Ohm’s Law, induce a current that, based on the PWM duty cycle, would be scaled in such a way as to move the needle on the meter to the corresponding hour, minute, or second.
One minor issue came up in the form of the max current the GPIO pins on the ATMega328 chip can source/sink. The pins can source/sink a maximum of 40mA, a bit far from the 60mA needed for the minutes and seconds meters. Enter the transistor.
Using a simple NPN transistor switch circuit, I was able to provide the current for the minute and second meters from the 5V supply. The PWM signals switch the respective transistors on and off, effectively varying the voltage across the resistors in series with the meters.
The resistor between 5V and the meter is actually 2 1/4 watt 100 Ohm resistors in parallel for an effective resistance of 50 Ohms. The two in parallel was necessary as 5V x 0.06A = 0.3W (more than 0.25 that a single 1/4W resistor can handle safely).
Meter clock: keeping “current” time - [Link]
A stable single transistor sine wave generator, that works with many values of input voltage. In PartSim you can easily change the value of the resistors and capacitors and observe the effect on the frequency of the oscillator. If you are manually calculating the frequencies, make things simpler by keeping the values of the resistors and capacitors equal (R5=R6=R7 and C1=C2=C3). You can see in the simulation that it takes a while to begin oscillating, and in ideal conditions it would need a signal to start oscillating, however in practice, noise begins the process without it.
2N2222 Phase Shift Oscillator - [Link]
Here’s Aon’s finished project the ytimer a visual feedback timer:
A countdown timer with super bright 7-segment displays that flash when the time is up, instead (or in addition to) an audible alarm.
The design is based on a PIC16F886 microcontroller which drives the displays using a TLC5916 LED driver and dual P-channel MOSFETs. A rotary encoder with a push button is used for input, in addition to two microswitches, one for power and one for toggling sound. The sound switch also toggles a green 0603 indicator LED.
The device is powered from two AAA batteries, which will hopefully deliver adequate battery life.
ytimer, visual feedback timer - [Link]
Want to build your own world clock? Check out Wouter’s DIY word clock instructables:
…I have found one DIY project that really stands out: Elektronika.ba’s wordclock, proving that it is possible to build your own wordclock that is as pretty as the original. Also, here is a video of the manufacturing process of the original: QLOCKTWO manufacturing
I have decided to build my own version, taking some queues from the sources in the above and making some changes (and adding some mistakes) of my own. Along the way, I have tried to take many pictures and I have written a build report in the form of this Instructable.
DIY word clock - [Link]
Johannes’ Numitron GeekWatch features Numitron tubes housed in a hideous 3D printed case:
Numitron tubes are cut-down version of Nixie tubes, but instead of having a wire-mesh anode with a cold-cathode display, uses a seven-segmented indicator commonly found on digital meters and clocks.
Old School Tube Watch - [Link]
A breakout board for the 555 timer exposing the leads astable or monostable implementation.
Hello, my name is Patrick Grady and I’m a highschool senior in the US. I’m an avid programmer and tinkerer and love anything related to electronics and computers.
This past winter I took a class in Digital Electronics and was introduced to the 555 timer. One of the most common applications of the 555 timer is the astable mode, which is unfortunately rather clunky to build on a breadboard. This 555 breakout board does more than expose the 555’s eight pins: it sets you up to run your 555 timer in astable mode with slots to insert two resistors and a capacitor of your choice. This board eliminates all the wiring for the 555 timer. The 555 Timer Breakout Board Plus will cut out the tedium of setting up the 555 timer and will allow hobbyists to dig straight in to their projects.
As a electronics hobbyist myself, I recognize the usefulness of this simple device, but also acknowledge its relevance is limited to the niche market of hobbyist electronics. If you want this device or think a friend could use it, please contribute to the campaign and buy a 555 timer breakout board!
555 Timer Breakout Board Plus - [Link]
Elia wrote an article detailing his binary wrist watch project:
I have just finished my binary wrist watch project (well, the new revision anyway). I was surprised at how small I was able to make it compared to last time.
I chose to go with the “super-yellow” color LEDs as they fit the purple OSHpark PCB very nicely. The biggest challenge was actually making a good looking wrist band for the watch. I originally intended to use a design like this but it turned out that due to lack of enough para cord I had left, I went with a simpler design that I had done once before.
DIY binary wrist watch - [Link]
Here’s a voltmeter clock project based on a multimeter clock design by Alan Parekh:
I have used three voltmeters and mounted them on a wooden plinth with a clear Perspex cover to give the clock an industrial look.
I have modified Alan’s code to run on PICBasic Pro version 3. I have also added the following.
Switched display On and Off (keeping battery backup as per Alan’s design) but also allows me to turn meters Off in full power mode.
Synchronization to my Master Clock every 30 seconds
Synchronized LED & Re-Synch LED
Synchronization On & Off
Transistor meter drivers
Separate hourly Chime Circuit
Pulsed “tick tock” seconds sound.
Voltmeter clock project - [Link]
Kyle wrote an article detailing his DIY automatic water timer:
Now that I have power and output figured out, I need to work on the control aspect. 555 timers are great for simple applications requiring up to a few minutes of delay. At 10 minutes, the RC values needed would boarder the danger zone of the timer not functioning correctly due to the leakage current of the capacitor and the small charge current of the resistor. I could have cascaded two or more timers together but that would be sloppy so I fell back on my trusty friend – the ATtiny micro controller. This would allow me to make changes as I want without redesigning the board.
DIY automatic water timer - [Link]
Kerry Wong writes:
As I mentioned in my previous posting, there was an issue with my Wavetek 907 microwave frequency generator. While everything was fine during my initial testing, the frequency display is now stuck with an out-of-range display and the adjustable frequency range is limited to between around 6.9 Ghz to 7.9 Ghz (instead of all the way up to 11 Ghz). My initial suspicion was that the PTC heater inside the YIG-Gunn oscillator was malfunctioning. But as it turned out, it was something else.
Since initially my gut feeling told me that the YIG oscillator might be at fault, I thought I would at least try taking it apart to see if it was something trivial to fix. And even if it is beyond economical repair, it would at least be a pretty interesting teardown of the YIG oscillator itself.
Wavetek 907 repair, YIG oscillator teardown - [Link]