Never mind the Buzzclock

Fair warning

So far, only one person I’ve told about this project thinks it’s a good idea. Everyone else looks at me wtih a mixture of pity and puzzlement, neither of which emotions seems to be mitigated by my explanation. Clearly, the best thing to do with the project is to bury it quietly, and where better to commit something to obscurity than on my blog?

A little bit of background

My eyesight is rubbish. With glasses on, I can see perfectly. Without them, I’m as blind as a bat. When I go to bed, I take off my glasses. If I wake up in the middle of the night, I am unable to find out what time it is without putting my glasses back on and looking at an illuminated clock. The problem is, that by the time I’ve done this (and waited for my ageing eyes to focus properly), I’m fully awake. If it turns out that it’s far too early to get up, it can take ages to get back to sleep.

The usual suggestions

Most people say “Can’t you get a clock with a big display?” It’s a logical suggestion, if you can see well. For me, the digits on a bedside clock would have to be about a foot tall for me to be able to read it without glasses. Others say “Can’t you turn on a light?”, but doing so brings me to full wakefulness (and runs the risk of disturbing my wife). Fools suggest “Can’t you just use an alarm clock?” I do. But if I wake up before it goes off, I want to know if it’s three hours before, or only one. If it’s only one, I’ll get up and do something useful.

The solution

Here it is, in all its glory:


No, it’s not the internet. It’s the Buzzclock. To use it, you press and hold the button on the top. It then tells you the current time by silently vibrating: one pulse for each hour, then one shorter pulse for each ten minutes past the hour. There is virtually no noise, no light and best of all no need to put on glasses. The time is not accurate to the minute, but it’s good enough to make the decision whether to get up or to go back to sleep.

Don’t laugh, it hurts my feelings.

Inside the box


It’s a bit of a squeeze. The brains of the device is an arduino Nano, connected to a battery-backed real time clock. The Nano is a very useful device – more or less the same functionality of an arduino Uno or Leonardo, but in a much smaller package. It’s also dirt cheap (about three of your earth pounds). You can plug it directly into a breadboard for prototyping, and then when you want to build the final device, you can solder it in to a PCB or stripboard, or you can plug it in to a terminal block breakout board, as I did.

nano adapter

The real time clock (RTC) module I used came from ebay, and also cost about £3. It uses a DS3231 chip, has a rechargeable backup battery and (unnecessarily) has 32k of flash memory on the same board. I guess the flash is there in case you want to use it for datalogging. The RTC chip also has a built in thermometer (I don’t know why).



The RTC and the arduino communicate over the two-wire I2C interface. This makes the wiring really simple. There are handy arduino libraries available to do all the heavy lifting. Thsi is a good thing, because the RTC chip has its own protocol for getting and setting the clock time, and the libraries wrap this into a nice simple set of commands.

The final component in the build is the vibration motor. This is one designed for mobile phones. As usual it’s from ebay and cost about a pound. This is a thing of beauty. It’s a small dc motor (it runs off 5V – the arduino can power it directly from an output pin) with an eccentric weight on its output shaft. When the motor spins, it vibrates. There is nothing special about that, except that it is tiny. The whole assembly is only about 10mm long. The engineering that goes in to mass producing those must be just staggering.


How it works

THe button is just a push-to close switch. As long as you hold it down, the arduino gets power. Let it go, and the power is cut. This way, the arduino uses no power at all when not in use. The RTC has its own backup battery, so it keeps track of time without using the main battery.

Every time you press the button, the arduino boots up. It then contacts the RTC to get the time from it, and sets its own clock. The output pin connected to the motor is brought high for half a second then low for half a second for each hour in the current time. After a full second pause, shorter pulses are used to indicate the tens of minutes after the hour. And that’s all it does. At four o’clock in the morning, when all is pitch black, its a very quick way of working out it’s too early to get up.

Setting the time

At the moment, you can only set the time by connecting the arduino to a PC and sending a string over the serial port. This is not a big deal, because the RTC keeps time over a long period. It’s only an issue when the clocks change to or from daylight saving time, and I can cope with the effort twice a year.

7 thoughts on “Never mind the Buzzclock

  1. What a wonderful, self-efacing article. If it works for you, why not? I’m fortunate enough to be able to see my projection clock after spending a couple of grand on laser surgery. Unfortunately, it is often several hours out, probably due to our concrete walls.

  2. Brilliant. What a great solution. You should produce them and sell them I am sure there are millions of people who need it.

    • It’s kind of you to say so, but I don’t think there are. I have yet to meet anyone who thinks it’s a good idea.

      • Maybe not millions, but what do you think of posting it to etsy or something where there is a very low monthly cost (i think 20 cents per item per month) and linking it here? Posting it up for sale may need a simpler way to program in the time like an LCD display and some buttons, but then it could be an extended function alarm clock. I mean, there are other buzzing time things, phone apps, sleeping alarms. I think blind people tell time with braille watches, but some group may find it.

  3. Very cool! And if it works, it works! I don’t think I have the mental fortitude when I’m half asleep though to count pulses…

    If you’re thinking of doing it again, same concept of ‘on only when held down’, but having LEDs project out onto the ceiling, and then just count the dots (maybe large dots, maybe a 9″ diameter on the ceiling, for hours and small dots, maybe 4 inch diameter, for tens of minutes) It might not be enough to wake someone, and my phone’s charging light is very visible on the ceiling at night.

    all in all, nice

    • Thanks for the kind comment. I did think of lights on the ceiling – indeed, I used to have a projection clock – but my eyesight really isn’t up to it without my glasses on. Counting the pulses really isn’t a problem. I only use it when I’m already awake enough to be trying to decide whether it’s too early to get up…

  4. Can I ask for a schematic of the circuit arduino and RTC, sir ?? I am currently in the process of learning to make a digital clock now. If the owner is willing, indeed I am very happy to receive knowledge from the master

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