Ohms Law Clock





Introduction: Ohms Law Clock

Epilog Challenge 9

This is an entry in the
Epilog Challenge 9

Here is one for the electronic geeks, which I am proud to say that I am one of them.

I am no expert in electronics, just a tinkerer, usually something associated with an Arduino.

However, sometimes I need to do some maths using Ohms Law and I can only remember two parts of it at a time.

If I try to remember a third, I forget one of the others. I think that I have an EEPROM issue in my brain.

Maybe I could swap out my brain for a number of Arduinos with extended EEPROMs as there is a lot of space in there. Maybe a future project.

We digress.

Ohms law is often described and displayed as a pie chart, split into four sections for Volts, Watts, Ohms and Amps, and each of the four is split into three sections for the appropriate equation.

Round pie chart with four sections and three parts to each section? hmmmmm, that makes twelve even parts in all. Looks like a clock to me.

Step 1: What I Had to Do

I found an old clock in my garage that was obviously surplus to requirements for some reason.

The plastic front has got damaged somehow. It looks like something has melted itself onto it???

I cleaned up the battery terminals and put a new battery into it, and to my surprise, it still worked.

I did a search on the internet with my favourite search engine for an Ohms Law pie chart, and came up with a lot of images.
There are lots and lots to choose from. Black and white, multi coloured etc. I went for a quite simple one in black on white. Easy for my useless printer to handle.

I loaded the image into my favourite, affordable, drawing package, and resized the image to the dimensions required for my clock and printed it out.

My clock is quite large, which is probably why it became surplus to requirements at the time, and has a clock face of 220mm in diameter. Too big for A4, but my useless printer also does A3, when it feels like doing as it is told.
I got there in the end after getting two unwanted A4 size cropped versions on A3 paper.
My image has a nice defined border to it, so it was easy to trim around it.

As I said, my clock has a damaged front, so it was built without a front. I’m sure that it will soon become a home for a lot of homeless dust particles.

Once the front was off (10 seconds), I gently prised the hands off one at a time, making sure that I didn’t mangle them in any way. The hands were surprisingly hard to remove on my clock, so if you are going to attempt something like this, beware!

Now that the hands were out of the way, it was just a case of making the correct size hole in my new clock face and gently gluing it in place. In my case, plan A was not so gentle and the face rippled, so I printed out another one for plan B. The glue that I eventually used was a simple and very cheap School/Office/Craft paper adhesive stick. (Pritt Stick, UHU Stick etc) My first attempt was with PVA because I have what is left of a gallon (about half) that I purchased for a woodwork restoration project that I did a while ago. Even though I was gentle, it just made the paper wet, and made a bit of a mess.

Once the face is on and looking cool, it was just a matter of putting the hands back on in the right order. Because mine were hard to remove, I was wary about the amount of pressure needed to replace them, but it worked out fine.

Step 2: My New Clock

I put the battery back in and it sprung into life. I got distracted at this time for about ten minutes and when I returned, the clock had the correct time. I had forgotten that it was a radio clock even though it had a symbol on the original face.

The clock is now on the wall of my workshop, just above my bench. I am hoping that the Ohms Laws will eventually sink in, either via osmosis due to close proximity, or just by being instantly visible all of the time.

Not an Arduino in sight!



  • Epilog Challenge 9

    Epilog Challenge 9
  • First Time Author Contest 2018

    First Time Author Contest 2018
  • Paper Contest 2018

    Paper Contest 2018

We have a be nice policy.
Please be positive and constructive.




Quick! Fix the Resistance Formula before anyone notices.
Notice that you have the formula at 5pm being the same as 11pm. 5PM is incorrect.
It is not "R=V2/R". It is "R=V2/P" (or more correctly R=E2/P). "P" for Power (Watts).

Don’t you just hate it when that happens :)

I was wondering why my circuits never work :)

Good spot.
Another lesson in not taking for granted what is on the internet.

Nice job but you do need to fix the “5 o’clock” error pointed out by Dave

Thanks, I had forgotten most of those formulas.

You should rotate all of the areas and formulas by 30° so that they line up with the hours on a clock

Great clock!

it is absolutely geeky!