Brains and Updated Vertical word clocks.

The recent clock building spurt resulted in my stock of clock brains being depleted. I went to make more only to discover that I had run out of the underlying circuit boards and was low on most of the other parts. So, time to stock up. Big order at digikey and another run of custom boards. I took the opportunity to update the circuit board design before ordering more. I designed this board using the pad 2 pad software package. It is free and despite not being an EE, I was able to sort out how to use it with relative ease. This revision to the board was a simple tweak to the screen printing. Boards were ordered and showed up within a week or so. They worked. I regret not adding a 2nd set of connectors for the LED strips. Those would help when those troublesome solder joints go wrong ( which is #1 issue when building these).

Word clock circuit board layout Revision 5.3

A quick tour of the clock brain

The image above shows the top side of the custom circuit board (same design with traces and ground plane removed is shown below).

On the top left, there is a place to attach the trinket M0. The trinket M0 is sold by Adafruit (a great place for electronic hobbyists). It is a small but powerful little micro controller that manages all the aspects of the clock. The dual rows of 5 pins on this board are designed to mate with the 10 pins on the trinket M0. The M0 is powered by the Bat+ and GND pins. If you follow the thin red trace from the Bat+ location, you can see how it splits with one path heading down towards the positive terminal on the big cap and the other path heading across to the 5v input on the upper right. Pins 0 and 2 to receive the time signals from the clock chip (labeled IC1 in the middle of the board). The M0 then determines which LEDs to illuminate (and what color) and sends the appropriate signal out of pin 1, through a 150 ohm resistor and then over to pin 2 on the level shifter chip ( lower right, labeled 74AHCT125N). The logic shifter converts the voltage levels on the logic signal from 3.3 volts (which is what the trinket M0 speaks) to 5 volts (which is what the LEDs want to listen to). From there the LED logic signal along with power and ground exit from the 3 wire connection ( labeled G 1 5v) in the middle of the right hand edge ( white, green and red wire trio on the photo below).

In the bottom center, we see the location for the 2 buttons that connect to pins 3 and 4 allowing adjustment of the time of day. These are cleverly labeled Min and Hours in hopes that I will not forget during clock assembly. The trinket M0 is connected to the buttons via pins 3 and 4. Normally, the M0 is weakly holding those pins at 3.3 volts. When the button is pressed, that pin gets connected to ground and the voltage drops to close to 0 volts. The M0 can detect this voltage drop and increments the time by an hour or minute depending on which button was pushed. The Rst pin (reset) and the USB+ pins are not used. The pin labeled 5v is supplying a weak pull-up voltage for the clock chip data pins which is likely not necessary given that one can set the pins on the M0 to have similar pull-up characteristics.

Same board design, showing the connections between components. The software, converts these to traces automatically.

The bottom left of the board is the place where a “big capacitor” lives. This is here to protect the LEDs from a power surge when the poser supply ( upper right) is connected. When power is first applied, this capacitor soaks up the surge before it can hit the first LED. The balance of the parts (mostly located in the upper center of the board are there to help the clock chip work and talk to the trinket M0. These include the crystal that provides a reference for the clock, some pull-up resistors (labeled 4.7k) to help make sure the conversation between the clock and the trinket is smooth, and a small capacitor that helps keep the clock running smoothly. Lastly, there is the backup battery holder (labeled 1250) which keep the clock running when there is no power. The large areas of red in the image are the ground plane which helps keep the entire thing from having issues with interference.

Below, you can see it almost fully assembled. The buttons are on the other side of the board. That way, the board can be mounted to the clock in a relatively neat fashion.

Word Clock board, stuffed. (missing the power connection and backup battery).

I used a few of the last batch of clock brains and a few of the new ones to power a new, shorter variant of the vertical word clock. The vertical clock is one of my favorite clock designs. The original version is great but a bit too tall to easily fit on my clock display book cases. The height is dictated by the dimensions of the available LED strips. In the taller original, I use 2 leds per word and leave every 3rd LED off. This help isolate each word from the others when illuminated. In this new, shorter version, I cut the height by 33% by decreasing the gap between words and not skipping every 3rd LED. So rather than being 60 LEDs high, this new design is 40 LEDs high. The perfect height to sit next to the large square word clock in a bookcase.

OG vertical word clock and large square word clock.

New shorter vertical word clock, next to large square word clock.

These new vertical word clocks are available at both the Track Park Gallery and at Compound Contemporary Gallery in a natural wood or black finish.