A kit for this activity is accessible from RSH Electronics.
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The ambit starts timing back switched on. The blooming LED lights to appearance that timing is in progress. Back the time aeon is over the blooming LED turns off, the red LED turns on and the bleeper sounds.
Adjustable 1-10 Minute Timer Project
The time aeon is set by adjusting the capricious resistor. It can be adapted from 1 to 10 account (approximately) with the genitalia apparent in the diagram. You can mark the times on a calibration fatigued on the box.
Please agenda that the ambit of time periods is alone approximate. With absolute apparatus the best time aeon should be 4½ minutes, but this is about continued to about 10 account because the 220µF timing capacitor boring leaks charge. This is a botheration with all electrolytic capacitors, but some aperture added than others. In accession the absolute amount of electrolytic capacitors can alter by as abundant as ±30% of their rated value.
This activity uses a power-on triggered 555 monostable circuit.
resistors: 470, 33k, 100k
variable resistor: 1M
capacitors: 0.1µF, 220µF 16V radial
LEDs: red, green
555 timer IC
8-pin DIL atrium for IC
battery blow for 9V PP3
stripboard 10 rows × 22 holes