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Transistor Wall Clock

transistorclock.com

62 pointskens28 comments

An interesting point would be that frequency of the AC power line is used for timing, what's more your supplier will generally try to normalize the frequency http://www2.nationalgrid.com/uk/Industry-information/electri... if if they're alternating too fast they'll slow it down to compensate and give an accurate long-term average.

I wonder if home-solar converters have this feature built in :)

Home solar converters will need to synchronize to the mains power supply like any generator before connecting. The power supply capacity of the grid is orders of magnitude more powerful, so connecting it out of sync will still cause it to sync, however, it most likely won't be pretty. Once it's connected, the grid will force it to stay in sync.

Here's a video of a generator who's synchronization system is being "hacked": https://www.youtube.com/watch?v=fJyWngDco3g Although the article doesn't mention it in specific, that's what the comments say is happening.

Similar project: http://techno-logic-art.com/clock.htm

I've seen that one before. Truly an amazing work of art.

I am just curious is it not be possible to use a crystal oscillator and hence not be dependent on the power line for timing? Are they not doing it just on principle i.e using only transistors, resistors, diodes and capacitors? I vaguely remember building an AM transmitter in high school using a crystal oscillator and transistors but no ICs.

You could use a crystal oscillator, but you'd need a bunch of circuitry to divide the frequency down to 1 Hz. The lowest-frequency crystal I could find is 20kHz. In other words, it's a lot easier to start with 60Hz than 20kHz when you're using individual transistors.

It's not that bad.. typically you use a 32.768kHz ("watch") crystal then divide by 15 to get one second. You can do it with two chips (a bunch of solutions, one is two 7468).

And how many transistors does that translate to?

Probably 30, but you dont need existing transistors needed to divide 60hz down to 1hz, so the change in parts count might be smaller.

Edit: Previously said 30, but it looks like its 60. Each JK flip flop takes 4 transistors.

Edit: Back to 30, the bistable circuit in the clock uses two transistors each.

You need 15 triggers to go from 32768 Hz to 1 Hz. Existing circuit uses 4 triggers to divide 60 Hz by 10 and another 3 to divide by 6. You can repurpose those so you only need 8 extra triggers. Two transistors each means 16.

You can also save 6 transistors from existing dividers because all divisions are by 2. So net total is 10 extra transistors for division, plus at least one in the oscillator itself.

To nit-pick, of course the division is not by 15 (that'd give 2,184.5333... Hz) but by 2 to the power of 15, i.e. 32,768. Typically implemented by a 15-bit counter.

I purchased and assembled this kit. It was fun, although it's pretty time consuming.

Do you want to get better at soldering? You'll get better at soldering. In fact, if your kit works, you'll have made 2700 good solder joints.

Would be cool to have a similarly exploded IC version next to it.

They have that: http://www.ttlclock.com/

Where is the vacuum tube version? I have always wondered if is possible to make complex vacuum tube logic circuitry just by hand in one big container and suck the air out. In this case in a glass container because you want those glowing clock numbers to show.

That's a lot of resistors. Makes me wonder about the power consumption.

Probably not very much power. Diode transistor logic with 10k and 100k resistors in a 9V circuit, worst case you're looking at about 1 mW per resistor. I suspect LED driving current dominates the power consumption of the device.

The manual (http://www.transistorclock.com/tranmanual.pdf ) has the spec. Answer: 5.7 Watts.

That is quite a lot. The table in [1] shows that an average 9V battery has a capacity of about 3.5Wh, meaning you can use this calculator for a little over half an hour on a single battery.

[1] http://www.zbattery.com/zbattery/batteryinfo.html

The product is called "transistor clock". It's a clock, for wall hanging, it's not a calculator and the images on the page of TFA show a power cable.

I guess it only counts time right with the (US) 60 Hz power supply? Then, it's strange that they made it show time in 24-hour format.

A lot of Americans use the 24-hour format by default.

Engineers generally use 24h time and SI everywhere on Earth (at least when engineering), regardless of local customs.

According to the website, you can just change a couple wires and it will work with 50 Hz power. This changes the divide-by-6 circuit to divide-by-5. http://www.transistorclock.com/50Hzmod.pdf

This is so cool. As an Electrical Engineer turned Software Engineer, this makes me miss working with hardware :(.

Just don't bring it to school with you.

Haha, came here to say that, you beat me to it.

Just don't make it look like a bomb on purpose, and take it out during English class, and then plug it in and set the alarm off.

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