The CSS555 low-power programmable version of the 555 family of timer ICs. It operates at a current under 5 µA and a supply voltage from 5.5V down to 1.2V. These qualities make it particularly well-suited for long lasting battery and small solar powered projects. It can be used in standard 555 configurations as supplied, but it is also user programmable to produce extended timing periods.
Author James Senft (a.k.a. TinkerJim) wrote an impressive 4-page article in the February 2016 edition of Nuts and Volts magazine. He featured some of the practical benefits and applications of the CSS555 illustrated by a few of his projects. The website www.instructables.com has further descriptions of two of these applications.
Jim has shared another project he made with the CSS555 (posted below); the Tinker Trolley.
Every winter season, it makes its rounds beneath the Christmas tree, its schedule being set by a CSS555 in astable mode with a long delay and a short run. It shuts down operations at night.
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If you have used one of TinkerJim’s instructables let us know how it turned out.
Another Application of the CSS555
In its extended or programed mode, the CSS555 is capable of very long period astable operation with a low duty cycle. This capability was used to make the operation of this model streetcar, now christened as the “Tinker Trolley”, much more interesting.
The little battery powered trolley was made over two decades ago to run around tracks set up beneath the Christmas tree (and as far beyond the region of the tree as the domestic authorities would allow the tracks to extend pending delicate negotiations each Advent). Originally, the streetcar had an ordinary toggle switch poking out of the roof to turn it on for its endless rail rattling runs. But then later, someone would have to go over to catch it to turn it off for a rest for the batteries – and for the ears. Eventually, tiring of these manual switching chores, the poor car often ended up just setting idle for long periods, even days sometimes. When the CSS555 became available, a perfect application for it was waiting! Thecircuit shown on page 18 of the “CSS555(C) Applications Circuits” document was cobbled up on a piece of strip board, mounted on the underside of the roof as shown in one of the photos, and the toggle switch replaced by a phototransistor. The circuit used timing components to give a period of approximately 3 min. with an on time of about 12 sec. (RA = 4M7, RB = 100K, RF = 100K, CT = .01µF, and multiplier M = 10K ). Now the trolley starts itself up, runs around its track layout once or twice, and then parks itself for a nice quiet interval, repeating this cycle all day long. This is a very satisfying operating regime for the trolley!
When at rest, the circuit draws only 6 µA. In addition, the Reset pin is connected to source VDD through the phototransistor and to ground through a 1Meg resistor. This arrangement puts the trolley to sleep at night and starts it on its rounds every morning. The streetcar thus operates autonomously for about five days on a pair of rechargeable AAA batteries. Just for variety, maybe next Advent, we might alter the operating schedule by reprogramming the CSS555, just changing the multiplier from M = 10K to M = 100K . Then Tinker Trolley would run for about two minutes every half hour !