Saturday, April 21, 2012 by skemarangkaian
Timer On-off 24 Jam. This is a circuits are multi-range timers offering periods of up to 24 hours and beyond. This circuit can be used as repeating timers - or as single-shot timers
While the oscillator is running - the 14-bit counter counts the number of oscillations - and the state of the count is reflected in the output pins. By adjusting R4 you can alter the frequency of the oscillator. So you can control the speed at which the count progresses. In other words - you can decide how long it will take for any given output pin to go high.
When that pin goes high - it switches the transistor - and the transistor in turn operates the relay. In single-shot mode - the output pin does a second job. It uses D1 to disable the oscillator - so the count stops with the output pin high.
If you want to use the timer in repeating mode - simply leave out D1. The count will carry on indefinitely. And the output pin will continue to switch the transistor on and off - at the same regular time intervals.
- Using "Trial and Error" to set a long time period would be very tedious. A better solution is to use the Setup tables provided - and calculate the time required for Pin 7 to go high. For example, if you want a period of 9 Hours - the Range table shows that you can use the output at Pin 2. You need Pin 2 to go high after 9 x 60 x 60 = 32 400 seconds. The Setup table tells you to divide this by 512 - giving about 63 seconds. Adjust R4 so that the Yellow LED lights 63 seconds after power is applied. This will give an output at Pin 2 after about 9 Hours.
- Ideally C3 should be non-polarized - but a regular electrolytic will work - provided it doesn't leak too badly in the reverse direction. Alternatively - you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors back to back
- The timers were designed for a 12-volt supply. However - provided a suitable relay is used - both circuits will work at anything from 5 to 15-volts. Applying power starts the timer. And it can be reset at any time by a brief interruption of the power supply.