Cool clock!

[SirNickity]

I saw this in the Make kit guide — really cool idea, and great job on the implementation. I built mine in an evening and it works perfectly.

Some ideas and observations for the tinkerers out there:

The gap behind the digital display
I didn’t want to have a large gap between the board and the digital display (call me OCD if ya like ;D) so I used some low profile resistors to help it sit closer to the board. It still isn’t quite perfect, but the offset is hardly noticeable. Another idea, if it’ll fit your mounting scheme, might be to mount them on the back and solder the top side.

(Incidentally, I used Panasonic ERO series resistors, but they are unfortunately now discontinued by the manufacturer. The Stackpole RNM series looks to be equivalent. These are available as a special order from Digikey. I put in an order for 500 of 10K 1% so we’ll see how that goes.)

The PM LED
So … I may have tried to use the board without reading the instructions first 😮 and like others, didn’t notice the caveat about the PM LED not being lit during operation. I wondered if it might be possible to use PWM to set the LED to partial brightness when it’s acting as an indicator, but still allow full brightness during detonation. Well… looking at the design and an Arduino pin reference, it appears the LED is connected to one of the Analog In pins, so no PWM. Bummer.

Maybe a possible fix would be to swap the 74HC595 pin 12 (ST_CP, or “latch”) and PM LED resistor pins (these are pin 25 [AIN3] and pin 5 [PWM3], respectively, on the micro). Now, I haven’t read the code, so I’m just assuming the latch isn’t driven by PWM — correct me if I’m wrong.

Anyway, just wanted to drop in say thanks for the kit.

[Michael]

SirNickity, thanks for taking the time to post. The latch isn’t driven by PWM, but both timer1 and timer2 are used by the clock (one to multiplex the display digits, and another for timekeeping), so most PWM pins aren’t usable for PWM. Pins were also chosen for ease of board layout. Good ideas, though!

Wasn’t aware of the low-profile resistors –thx for the info.

Now, I hope you build a cool looking clock for the gallery!
http://nootropicdesign.com/defusableclock/gallery.html

[Author]

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