Search RFCafe.com                           
      More Than 17,000 Unique Pages
Please support me by ADVERTISING!
Serving a Pleasant Blend of Yesterday, Today, and Tomorrow™ Please Support My Advertisers!
   Formulas & Data
Electronics | RF
Mathematics
Mechanics | Physics
     AI-Generated
     Technical Data
Pioneers | Society
Companies | Parts
Principles | Assns


 About | Sitemap
Homepage Archive
        Resources
Articles, Forums Calculators, Radar
Magazines, Museum
Radio Service Data
Software, Videos
     Entertainment
Crosswords, Humor Cogitations, Podcast
Quotes, Quizzes
   Parts & Services
1000s of Listings
 Vintage Magazines
Electronics World
Popular Electronics
Radio & TV News
QST | Pop Science
Popular Mechanics
Radio-Craft
Radio-Electronics
Short Wave Craft
Electronics | OFA
Saturday Eve Post

Software: RF Cascade Workbook
RF Stencils Visio | RF Symbols Visio
RF Symbols Office | Cafe Press
Espresso Engineering Workbook

Aegis Power  |  Alliance Test
Centric RF  |  Empower RF
ISOTEC  |  Reactel  |  RFCT
San Fran Circuits

Crane Aerospace Electronics Microwave Solutions



Temwell Filters

Please Support RF Cafe by purchasing my  ridiculously low-priced products, all of which I created.

RF Cascade Workbook for Excel

RF & Electronics Symbols for Visio

RF & Electronics Symbols for Office

RF & Electronics Stencils for Visio

RF Workbench

T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads

These Are Available for Free

Espresso Engineering Workbook™

Smith Chart™ for Excel

RF Cascade Workbook 2018 - RF Cafe

Build a Candle Snuffer Using a 555 Timer
Cool Product Report

Featured Product Archive

The inventions and products featured on these pages were chosen either for their uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough to warrant an appearance.

| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 |

<Previous                     Next>

 

Signetics 555/556 Timers 1973 Databook - RF CafeA couple days ago I posted an update on the Watkins-Johnson databook page that had an unauthorized gag graph titled, "WJ-G1/SMG1 Phase vs. VCTL vs. Frequency vs. Phase of the Moon." When RF Cafe visitor and sometimes contributor Dr. Marek Klemes* read that, he sent me a note about remembering this "Delayed Light Turn-Off" circuit from the Signetics 555/556 Timer Databook. It took a bit of creative Googling, but he managed to find the datasheet (to the right). The text was a bit washed out from the original low resolution scan, so I reproduced the labels (green).

Signetics NE555 timer schematic for a "Delayed Light Turn-Off" circuit - RF Cafe

Signetics NE555 timer schematic for a "Delayed Light Turn-Off" circuit from their 1973 databook.

This Rube Goldberg-ish contraption works thusly:

After a delay determined by the values selected for R1 and C1, the output of the NE555 timer goes high and causes resistor RL to heat up enough to ignite match M1. M1 subsequently lights the fuse on firecracker FC1, which has tied to its body a string that wraps around a pulley and holds a rock (which weighs precisely 2π pounds) suspended in space atop a bellows. Once the firecracker explodes, the rock falls on the bellows, causing a puff of air to snuff out the targeted candle.

Highly predictable timing is made difficult by the variability of the fuse burn time, the time required for the rock to compress the bellows, and for the air blast to reach the candle flame. The time of flight of the rock is calculable with the first-semester physics free-fall equation of t = √(2h/g), but empirical measurements are required to determine the fuse burn time, bellows compression time, and subsequent air puff travel time to the candle, which compared to time constant of the R1/C1 combination, is quite imprecise.

Signetics databook comic drawings NE555 timer - RF CafeThe same Signetics 555/556 databook includes a half dozen or so comic type drawings to help readers grasp the concepts of integrated circuit timer applications. In some aspects it is rather insulting, although it was probably the ploy of the same engineers who dreamed up the "Delayed Light Turn-Off" circuit. I remember being amazed while in the U.S. Air Force seeing manuals in the vehicle maintenance shop that were made to look like comic books, illustrating how to perform tasks ranging from changing oil on a 2-ton truck to overhauling a diesel engine. That was done due to a directive that the manuals be comprehendible by someone with a sixth-grade education. Now that was insulting.

 

* See "Therapeutic Radio," "In the Days of Spark - A Rescue at Sea," and "Standards of Measurement."

 

 

Posted December 7, 2018

RF Cascade Workbook 2018 - RF Cafe
PCB Directory (Manufacturers)



withwave microwave devices - RF Cafe