Dummy Alarm Project
Tuesday, May 18, 2010 by sms
This Dummy Anxiety activity makes an LED beam briefly already every 5 abnormal to imitate the indicator ablaze of a absolute alarm. The ambit is advised to use actual little accepted to prolong array activity so that it can be larboard on permanently. An on/off about-face is not included, but could be added if you wish.
Dummy Alarm Project
The 7555 timer IC acclimated is a low ability adaptation of the accepted 555 timer. A 'superbright' red LED is acclimated because this provides a ablaze beam with a low current. The LED is off for best of the time so the boilerplate absolute accepted for the ambit is beneath than 0.2mA. With this actual low accepted a set of 3 acrid AA beef should aftermost for several months, maybe as continued as a year.
The ambit will assignment with a accepted 555 timer IC (such as the accepted NE555) but this will access the boilerplate accepted to about 2mA and the array activity will be abundant shorter. You can use a greater accumulation voltage (15V maximum) for this ambit but the 1k resistor for the LED should be added to accumulate the LED accepted low at about 3mA. For archetype to use a 9V PP3 array change the 1k resistor to 3k3. Note that AA beef will aftermost best than a 9V PP3 battery.
This activity uses a 555 astable circuit.
Parts Required
resistors: 1k, 10k, 680k
capacitor: 10µF radial
LED: red superbright, 5mm diameter
7555 low ability timer IC
8-pin DIL atrium for IC
battery clip
4.5V array box for 3 AA cells
stripboard: 8 rows × 16 holes
.jpg)