Old Technology: Mechanical Automation sequencers.

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
26,291
I was doing some sequence routine programming in Assembly, and recalled the old method of mechanical sequencers.
Not sure if anyone remembers or are familiar with them, but I oddly I could not find any reference to them on the WWW.
The typical one had a drum with rows of raised points on it and as it rotated slowly or indexed, the points would close a contact in the circuit, in order to activate it.
It was a simple form of pre-PLC control etc.
Anyone recall them?
Or have a link?
.

.
 

SamR

Joined Mar 19, 2019
4,492
There were some clockworks with flat circular disks very similar to a disk recorder. Except the disks were brass/copper? with punched "bumps" on them to activate a limit switch type mechanism. That had to be at least 1940-50s technology (if not earlier). Don't recall ever seeing a drum mechanism other than in a picture or illustration.

Aha...
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Industrial Timer Company - Programmable Timers
 
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Jon Chandler

Joined Jun 12, 2008
433
Big Clive on YouTube has a great video on animated neon sign controllers. The first part of the video talks a bit about the history of neon signs, while the last part shows one of the controllers in action. Very much worth a watch!

Clive provides a number of links about these signs in the description of the video.

He also provides a link to Great Lakes Sign Products who still manufacture and sell these mechanical sign controllers!
 

Thread Starter

MaxHeadRoom

Joined Jul 18, 2013
26,291
There were some clockworks with flat circular disks very similar to a disk recorder. Except the disks were brass/copper? with punched "bumps" on them to activate a limit switch type mechanism. That had to be at least 1940-50s technology (if not earlier). Don't recall ever seeing a drum mechanism other than in a picture or illustration.
Those are very similar, this was back in the '80's when I came across them, the last I remember was in a Plant that was associated with the milk processing plant.
 

Ya’akov

Joined Jan 27, 2019
6,857
I was doing some sequence routine programming in Assembly, and recalled the old method of mechanical sequencers.
Not sure if anyone remembers or are familiar with them, but I oddly I could not find any reference to them on the WWW.
The typical one had a drum with rows of raised points on it and as it rotated slowly or indexed, the points would close a contact in the circuit, in order to activate it.
It was a simple form of pre-PLC control etc.
Anyone recall them?
Or have a link?
.

.
When I was working at the Boston Museum of Science they were very common in exhibits. As @vu2nan points out, we knew them as cam timers. I just starting trying to get PLCs into exhibits as replacements when I moved on, particularly for exhibits that really needed sensors like temperature rather than hoping time would remain constant.

[EDIT: typo corrections and insertion of mysteriously missing words to make sense.]
 
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SamR

Joined Mar 19, 2019
4,492
The early PLCs were a rear bear to work with, horribly expensive, low I/O count, and their "Tape" drive was a cassette tape deck. Note that in this rack chassis only 1 card was I/O but you could buy an expansion chassis. Can't remember the count but not much (8-16 contacts?). Honeywell developed them to be used as package boiler burner controllers. We weren't even able to program them and had to depend on Honeywell so they basically never changed after installation. Tape backup was only used if and when they became corrupted and had to be reprogramed. One reason why clock based mechanical ones remained in use for so long.
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Reloadron

Joined Jan 15, 2015
7,084
The typical one had a drum with rows of raised points on it and as it rotated slowly or indexed, the points would close a contact in the circuit, in order to activate it.
I remember them well. Worked with ones driven by small shaded pole motors geared down driving a shaft of cams so they had dwell times. Some had a dozen micro-switches on them. The cam lobes were adjustable. Most had been running since the mid 60s so about 30 years service when I worked with them early 90s. Just like pictured in post #8 and post #4.

Ron
 
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MisterBill2

Joined Jan 23, 2018
13,808
I still have one of those cam timers that ran a spot welder. 3 cams and a solenoid to engage the clutch to start the cycle. Clap, close, weld, release. It has a synchronous motor so the times are always the same. Quite a museum piece. And it cost more then than a small PLC from Automation Direct costs now.
 

Ya’akov

Joined Jan 27, 2019
6,857
look mum no computer on youtube had a project using what I think you're looking for. The devices get a signal and they increment one step around the device. He has a video explaining the operation.
Here is a link to his projects page on it.
https://www.lookmumnocomputer.com/projects#/electromechanical-visitor-counter
While pretty neat, uniselectors (a kind of stepping switch) aren't the cam timers (a time-based sequencing switch) the TS was looking for. Cam timers have discrete switches (I've only seen microswitch versions) that are mounted on a rail above one or more cams sharing a common shaft driven by a small motor. The cams have set screws to hold them to the shaft, so can be rotated around as needed. The cam is made of two pieces that overlap so it can be adjusted from a complete, uniform disk to a cam with a notched edge up to about 50% of the circumference.

When the motor is energized and the shaft rotates, the switches are operated by the cams according to the notched part. If the notch under the switch actuator it remains in the normal position. If the cam is full size, it operates the switch. By clever adjustment of the rotation and size of gap or non-gap depending on your point of view, complicated timing sequences with make-before-break and break-before make switching can be created.

The maximum sequence time is dependent on the speed of the motor. Most cam timers I have seen use small synchronous motors and so offer one sequence length. But I have seen speed adjustable versions. The variety of never uses of cam timers is impressive. One or more timers, combined with latching relays, can do some pretty sophisticated things. (They could even be combined with uniselectors!)
 
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