
Transistor Wall Clock - kens
http://www.transistorclock.com/
======
baxter001
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...](http://www2.nationalgrid.com/uk/Industry-
information/electricity-transmission-operational-data/) 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 :)

~~~
tcas
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](https://www.youtube.com/watch?v=fJyWngDco3g)
Although the article doesn't mention it in specific, that's what the comments
say is happening.

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dperfect
Similar project: [http://techno-logic-art.com/clock.htm](http://techno-logic-
art.com/clock.htm)

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jack-r-abbit
I've seen that one before. Truly an amazing work of art.

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pthreads
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.

~~~
kens
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.

~~~
dynode
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).

~~~
javawizard
And how many transistors does that translate to?

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pps43
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.

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IvyMike
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.

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

~~~
jccooper
They have that: [http://www.ttlclock.com/](http://www.ttlclock.com/)

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timonoko
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.

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

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

~~~
amelius
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](http://www.zbattery.com/zbattery/batteryinfo.html)

~~~
unwind
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.

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listic
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.

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

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huangc10
This is so cool. As an Electrical Engineer turned Software Engineer, this
makes me miss working with hardware :(.

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ganeumann
Just don't bring it to school with you.

~~~
Houshalter
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.

