Simple photographic timer is a simple count down timer with six preset times.60,90.120.300,600 and 900 secondsAt powerup the default count time is 60 seconds. pressing sw1 sycles through the other timing delays.At the end of the count the output goes low for two seconds and the times then reset back to the preselected value and starts again.The project presented here is based on world’s most powerful micro-controller based on intel’s mcs-51 family , generally known as intel-8051. We have used its derivative atmel-89c2051.
Main features: 4digit 7segment led display and a open collector output which can be used to operate, relay or buzzer or what ever you want at the end of timing period.
There are three inputs to the circuit. reset ,start and pause .Reset input is for hardware reset.
all inputs are pulled high, or may be pulled low by switched or relays, by the open collector transister Q7. Two switches are also connected along with the start and stop of the inputs. so that you can test the basic function of the module.all the inputs and outputs are connected to 10pin header connector.
Inputs:
This timer has three inputs and one output.
Reset: it makes the countrer to show 0060 default valur
Start : will load the count value by 60,90.120.300,600 and 900 seconds
Pause : will pause the timer pressing start will again start the timer
Out: overflow will cause this low going pulse output from this pin.
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