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Using the electric utility frequency for timekeeping — How accurate is it?

The Analog-Style LED Clock uses the 50 or 60Hz from the electric utility as a time base to keep accurate time without the use of a crystal oscillator. The clock automatically detects whether it is connected to 50 or 60Hz and adjusts accordingly.  A question I’m often asked is “How accurate is the electric utility frequency?” The short answer is that it is surprisingly accurate.

In the 1920’s Laurens Hammond invented an electric clock driven by a synchronous AC motor. It kept time using a motor that was in sync with the 60Hz frequency generated by the utility companies. He gave away hundreds of these clocks to power stations as an incentive to maintain a steady frequency which allowed his inexpensive clock to be used anywhere in North America. Hammond went on to help create the Hammond Organ which used a synchronous AC motor to drive a “tone wheel” generator which created perfect pitches for the organ.

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Analog Style LED Clock now available on Tindie.com

The Analog Style LED Clock is now available on Tindie.com! Tindie is a marketplace for maker made products. They have over 4,000 products listed from makers like me.

Tindie adds layers of protection for both buyers and sellers. For example, they will hold your payment until your order has shipped. Check out the Tindie Guarantee!

I sell on Tindie

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The Kit is Available!

The Analog Style LED Clock Kit is available to purchase! My goal when I decided to sell it as a kit back in June, was to make it available by December 1. June sounds like a long time ago, but the time really has flown by fast!

I missed my target release date by a week. I guess that’s not too bad. Especially since it’s still in time for Christmas! Hint, hint! 😉

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New website is live!

I just went live with the new site! Got some more tweaking to do, but it’s about 95% complete. Feel free to check it out! In particular, you might want to head over to our Downloads page and check out the user’s manual – complete with operation & assembly instructions, troubleshooting, theory of operation and schematics.

I anticipate that the kits will be available in about a week. If you have any questions or feedback about the site, please don’t hesitate to contact me.

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Built new board

I got my new PCBs earlier this week and they look great! I built a board today, taking pictures as I went to put in the assembly manual. The board looks and works perfectly! Now I have to update the manual, make a couple of tweaks to the firmware, and add ordering capability to the website.

Speaking of website, I’ve been working on a new site using WordPress and using the WooCommerce plugin. I’m really impressed with the capabilities of this software. A bit of a learning curve, but it’s allowing me to create a very capable and professional looking site! I’m really looking forward to going live with the new site!

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1st kit built

Keith finally got time to assemble his clock. It came out looking great! There were a few issues with the assembly instruction, but other than that, there were no problems.

Now that Keith has built his clock, and I have his feedback, I can proceed with re-spinning the board. While waiting for his feedback, I completed the rest of the manual. I just need to update the assembly portion with new pictures and make some adjustments to some of the instructions. And I assembled more kits. The components will all remain the same — just need to add the new board and manual.

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1st kit delivered

This is an exciting day and a milestone in developing the LED Clock kit!

I delivered my first kit to my friend and coworker, Keith, who also owns KABtronics.com. He has been a great inspiration to me in developing this project into a kit. Keith will be giving me valuable feedback on building the kit and proofreading the manual for clarity, mistakes and omissions.

At this point, the manual is not complete, but has instructions to build and operate the clock and some general troubleshooting information. Also, the PC Board will need to be re-spun to incorporate the additional diode and correct some markings. While I’m at it, I will be making some other enhancements to the board as well. At this point, I’m thinking I’m about 6 weeks away from having a finished product.

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Fixed alarm sound

I fixed the alarm sound. With the Senior Project clock, the buzzer and the buttons were connected to the same port. On the new clock, they were connected to different ports. I did not update the button reading routine correctly, so the buzzer output was not working at the moment a button was being read. This resulted in a little distortion being introduced into the signal going to the buzzer. This was easily fixed once I figured out what was causing the problem.

However, I made a discovery while troubleshooting this problem. While looking at the buzzer’s waveform on an oscilloscope, I saw voltage spikes being generated by the buzzer’s coil. I realized that I needed to add a diode to the circuit to protect the microcontroller from these spikes.

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Built the prototype

I assembled the first board, using a Zero Insertion Force (ZIF) socket for the microcontroller. The socket has a lever to release the microcontroller so it can be inserted and removed without any force. This allows it to be removed a lot easier for programming.

I adjusted the code for changes in the pin assignments and got the new clock working, except the alarm sounds strange. I suspect it’s a software issue of some sort, but will have to troubleshoot it later.

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