A Bit Big for a Bit, But

Right on, @blindbento! I like the example project ideas and the way you are thinking of this module as also being a digital pulse-timeout combo.

@chris101, how about replacing the imaginary segmented LED’s with an LCD Display? Then you could monitor your WWVB signal on screen with a mode button, clean up the clown barf, and reduce to one output.

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Yep, the only ways to get very delayed signals is via the cloud bit or the Arduino bit at the moment. However, both can do far more interesting things than keep time. :grinning:

If it is possible to add an LCD like on the oscilloscope bit, that would be fantastic. All of the pots and switches could be replaced with one encoder/button combo.

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@blindbento, I really dig that lucid-dream mask! I played with ld back in the day and it’s an amazing experience. :man_with_turban:

Displaying the time is not the main thing this bit does: it’s purpose is to provide analog representation of the time that works in the littleBits system. I had considered using slow serial data previously, but decided instead to represent time with continuously increasing voltages.

I can think of two ways to handle alarms: internally with a specific pattern of discontinuous output, or externally, using for example an arduino or threshold bit.

[quote=“blindbento, post:28, topic:22739, full:true”]
… As the WWVB signal also accounts for daylight savings, there would be no need to rewrite the code on the Arduino to account for that. :smile:

Both WWVB and the DS3231 on the Chronodot handle DST (although I live in DST-free Arizona :sunglasses: ), leap years, and leap seconds!. This is a huge bit of work off the software!

I’ve looked at LCDs, but I have also thought about nixie tubes!

They go well with the metal can transistors and 1960’s ULF radio transmissions, eh? :wink:

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If you can come up with lots of examples where converting an analog time signal to binary on/off switch is a must, wouldn’t it be better to have that right on the bit? :grinning:

I think that the final bit would be two bitSnaps tall due to the size of the components. This would leave room for an analog time out. That could be changed for seconds/minutes/hours output. The hours output should be 0 to 23 for a full day.

With just these two outputs, several experiments could be done to measure the accuracy of two clocks. Going back to your original day clock, you could use the alarm to mark when your clock actually did wrap over to a new day using a cloud bit. This way you can have it appear in a nice spread sheet without having to stay awake and write down the time manually. :calling:

Most of this advice is for if this is not a one-off bit. I think that Nixie tubes are cool, but they are pricey for commercial production. :moneybag: When it comes to making thousands of units, even a savings of ten cents can make a major difference in the final price.

I’m glad you like the idea for using littleBits as a lucid dreaming aide. I’m not sure it would be so simple without an alarm function. :sweat_smile:

Yes, please use Nixie tubes, and while we’re at it, let’s ask @Philip_Verbeek to put vaccuum tubes on his radio bit. :slight_smile:


Haha, That would be sooo cool. I like it!

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I love tubes - they are so cool and so retro, but for the sake of ease of use and design, I am so glad that we have solid state now! I will however keep my eye out for some cool nixies. Never can tell when they’ll be needed! I read somewhere though that 7 segment LEDs are almost as nostalgic. I don’t see it, but then I have a bunch of those!

@chris101, look at this Robot by @drthuler! The kids put a clock in Robot’s belly! :slight_smile: :clock1030:

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Very cool! Clocks are in right now, and those kids know it. :smile:

Hey Diego (@drthuler), what kinds of features would you like in a time bit (especially, as the kids in your chapter have used a clock already)? Join in if you have any ideas!

I’ve not had much ‘bench-time’, but have been working through some of the ideas from the conversation with you, and @blindbento as noted above. I added a display, especially for those who would want to use the time bit as a clock:

This also relieves the output bitSnaps of their ‘clock’ duties, and they can do alarms, timers, or the original analog H, M, S. I ran out of board space, so, just like Manhattan, it’s built ‘upward’. This configuration, with the display above the antenna, is not ideal though.

As you can see here:

the antenna is pretty crowded.

When the display is powered on (it doesn’t even need to be active), there is RF interference, and the error rate when receiving the time from WWVB doubles. It can take much longer to lock on to the time, and the times of availability are limited to a few hours after midnight. If I elevate the display another centimeter, then everything is fine.

I am also considering making the display separate and optional.


Hi Chris @chris101,
Nice multi-storage bit !
Can you make a little bullet summary of all the functions you now have built in?

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I’m sure that most of the components on the lower part of the circuit would be on the underside of the PCB.

The antenna would on the upper part of the PCB with the clock display LEDs on the lower part where all of the digital logic is. That should avoid interference.:satellite:

I cant wait to see what else you can accomplish with this bit now! :grinning:


Hey Alex, @alexpikkert

I’m always open to suggestions, but I want to stay within a simple philosophy for this device. Like all littleBits modules, it’s actions are easy to understand, and limited. First and foremost, this is an input module that knows the time, and can inject it into a littleBits circuit. But it also has some special features, because, … I mean you just HAVE to, right?

Right now it has these main features:

  • keeps the time accurately to the exact second,
  • outputs analog time through three bitSnap connectors, hours, minutes and seconds. Analog time can be used to drive an analog or digital clock, engage with a circuit that needs to know the time, activate alarms, etc. It can even keep track of the music using the synth kit.),
  • displays the current time with either an optional or built-in digital display,
  • keep track of how long it has been since it’s last setting, and resets automatically by contacting ‘ulf’ radio station WWVB. (The device can be configured to receive WWVB in Colorado, MSF in the UK, DCF77 in Germany, or two different frequencies of JJY in Japan. Right now, this would need to be set up at manufacture time, however a new chip and antenna from C-Max promises automatic transmitter switching. I have a CME 8000 chip in this device, but do not have the less than an inch long CMA-MF multi-frequency antenna… yet!) Here is a map of world-wide coverage:

  • ‘clown barf’ display (flashing pink, yellow, green, blue and red super-bright LEDs) is a visualization of WWVB’s various states. ‘Clown barf’ is displayed while the time is being set by WWVB. ‘Clown barf’ can be turned off with a toggle switch. The switch ‘clicks’ satisfactorily,
  • time can be set on demand by momentarily pressing the ‘set’ button. When this happens, the device contacts WWVB, and then sets the clock to the received time.

I’m working on manual setting, alarms, and timers:

  • if the ‘set’ button is held down, the time can be set using three pots, representing hours, minutes and seconds. When the button is released, the time continues from the new setting. NOTE: within a day, the device will contact WWVB, and the time will be reset to the Real Time, unless WWBV receiver has been turned off,
  • alarms are set by selecting ‘alarm’ on the ‘mode’ switch and setting the time as described above. When the switch is returned to ‘time’ mode, the clock returns to normal operation, but the alarm time is remembered. When the alarm time happens, the ‘clown barf’ comes on, and HIGH LOW HIGH LOW pulses are sent to all three analog outputs,
  • timers can be set on any of the outputs. In ‘timer’ mode, the time is set, and then counts down to zero. When zero is reached, the alarm sequence happens - barf, and pulses on the selected output.

Some hardware features:

  • the WWVB radio, Arduino microcontroller, and Chronodot RTC can be turned ‘off’ by putting it into a low power sleep mode. While sleeping the device consumes less then 25 microamps,
  • a lithium battery keeps the system alive, but in sleep mode, when it disconnected from power. Nothing is displayed, but the time, alarm progress, and timers continue to run. Nothing happens when they reach completion while in sleep mode,
  • The device is sized so that it connects with the arduino bit and the wireless transmitter. The foot spacing and underside clearance is such that it fits onto a mounting board.
  • A 5 female pin header brings the sda, scl, ground, +5v, and +3.3v out for connection to a user device. This can also be used to time-sync computers, TVs, and other digital equipment. I’d like to make this a better connector, but what is close and standard?

That’s my current (and near-term) feature list. What else does it need?


Hi Chris @chris101,
thanks for this nice detailed overview, now it is much easier to think about the design…

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Hey @blindbento!

I’m not even close to designing a double sided pcb for this! If it ever gets to that stage (and I am not counting on that happening) I will leave the design of the manufacturable device to professionals. I’m just building some devices (I’ve got 4 of them now) that I can work out some ideas.

The added display works nicely, but it’s causing big problems for the radio. I moved the display device from the upper left of the board, above the antenna, to the lower right corner, and it still interfered:

The culprit may be the two 72mm leads that connect to the display module. When the display powered off, everything is fine, the radio receives the signal normally. As soon as the twi signal is turned on - even if the display is off, the interference starts. First thing I’m gonna try when I get a minute, is shorter leads. I would prefer to put the display back up above the antenna. But if that is not possible, I’ll need to do some major re-designing of this device.

Another thing I need to do is change the way the output opamp and filter resistors/caps are wired up. Not for RFI, but for output impedance and current. You may notice I’ve removed some parts around the OPA4342.

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Cool, thanks Alex! I look forward to your ideas.

It’s been 6 months, so I want to give an update on this:

I have made several hardware mods, and have taken many of your suggestions into the design. The Atomic Clock has been running every day for over 5 months now, syncing the time as needed to keep perfect accuracy. It is always within one second of UTC.

Here it is, being used in my house as a radio time beacon:


Hello can you help me? I’m looking for the op amp used in the littlebits, I saw that you bought it. I’m confused with so many options that appear to me when I type LMV321z on google, haha. I would also like to know what is the SOT353 that you mentioned. thank you !

Hi @Eduardo_1448. I think the lmv321 chip only comes in smd packages. I searched Digikey, and sot353 is the package they had. I only tried etching and using smd parts this one messy time:

After that I decided to use thru hole op amp. I found a rail to rail thru hole dual op amp that Adafruit sells: TLV2462. I’ve used it a bunch and really like it. Here’s the link: https://www.adafruit.com/product/808?gclid=EAIaIQobChMI8Mye-a6A4AIVSsDICh0xwwVQEAQYASABEgLS7_D_BwE

I hope that helps. What are you making, if you don’t mind me asking?


Hi @Eduardo_1448, (and hello again @JackANDJude!)

According to the TI datasheet, Jude is correct when she says the LMV321 is only available as a surface mount device. The clock in this thread uses a 14 pin device, the OPA4342, which has four opamps on a single chip. I bought them on ebay. They fit the requirement to buffer one input and three outputs perfectly. Like the LMV321, the OPA chip is rail to rail (input and output), but the 321 can source much more current (60mA for the LMV321 vs 16mA for the OPA4342.) On the other hand, having four opamps in a single chip is useful when using bulky through hole chips.

There are other rail-to-rail opamps available to the hobbyist market as well. I too have used the TLV2426, for example in this 8 bit clock which needs only 2 amplifiers:

If you want exactly the characteristics of the LMV321, Sparkfun has a breakout board for the LMV358, which is the dual amp version of the LMV321.

Have fun in op-amp land!