Some electric clocks that you might find interesting. - Page 1
Forum section: electronics / general

author: lmester
author_rank: Regular Contributor
timestamp: March 04, 2018, 04:35:05 am
content: In another post, a reader noticed these clocks sitting in the background.My training is in electronics. A hobby of mine is collecting and repairing clocks. Probably not a common combinationThese clocks might be of interest to electronics enthusiasts. I have a large number of purely mechanical clocks. The two clocks in the first picture are styled to look like mechanical 400 day torsion clocks. They're actually more modern designs and are both battery powered.At first you might think that these are both quartz clocks. Notice that the one on the right does not say "quartz" on the dial.The clock on the right is an older design. It uses a one transistor circuit driving a coil. This provides the impulse needed to keep the pendulum rotating. A sense coil is used to trigger the circuit when the magnet passes over the coil. Both coils are wound on the same bobbin. The pendulum is used as the timebase to regulate the clock. There is an aluminum disc next to the blue capacitor. This is an eddy current brake. It's used to regulate the pendulum rotation. Many variations of this type clock were sold before quartz clocks became common. For more info on these clocks enter "ATO clock" into your favorite search engine.The second and third pictures show the electronics in this clock.The clock on the left is an early mass produced quartz clock. You can see the date code on the I.C. 7803. It's about 40 years old. It uses a Lavet type stepping motor to drive the movement. The Lavet motor is a single phase stepping motor that has a preferred direction of rotation. You can see the rotor in the lower right of the picture. A nice feature of this clock is the yellow trim cap on the left. That makes it convenient to adjust the clock.The pendulum on this clock is just there to make it look like a 400 day clock. It's not used as the timebase. Also, it's rotated by a circuit very similar to what's in the first clock.That 8 pin DIP on the board is what made inexpensive quartz clocks possible. Before these ASIC's were available, the circuit needed to lower the crystal frequency to a usable value was complex and expensive.The fourth and fifth pictures show this clock.Just how complex is shown in the last four pictures. This board and plug in cards are from a simplex master clock. It has a 1.6384 MHz TCXO. This frequency is divided by 32768 to produce 50Hz. The 50Hz is then amplified and used to drive a synchronous clock motor. This shows how crazy it was to use discrete transistors to make a 15 stage divider!

author: james_s
author_rank: Super Contributor
timestamp: March 04, 2018, 05:43:07 am
content: Clocks can be fascinating. One of my favorite clocks is one I found for a few dollars in a junk store. It's a 7-segment digital clock but purely mechanical with a pair of incandescent lamps to backlight it. When I found it the bulbs were burned out, I'm sure most of them got thrown out when that happened as you have to take the the back off to get to the bulbs.

author: lowimpedance
author_rank: Super Contributor
timestamp: March 05, 2018, 10:38:18 am
content: Thanks for the pictures, most interesting. As for electronics and clocks as a hobby combination, it may not be as uncommon as you think