Below we have a typical circuit of a timer, using the common 555 IC.
This is a standard configuration, and all possible configurations have been catered for. (most common applications)
For a positive incoming pulse, a transistor is used as an inverter, as the pulse required by the IC is a negative going one.
The connection on pin4 will be a reset option (negative going pulse), the connection on pin5 will be a external adjustment to alter timing function. The relay can be used or left off and then the output will be on either S1 or S2. Use the table on page 1 to get the time delays required.
The layout is seen below, from the component side, and from the track side. On the layout all components are shown, but in any application some of the components are not needed, in fact they have to be left off, otherwise the circuit will not function as desired. Pages will be added where other diagrams and layouts will be given, for assembly of other configurations..
Cost of this Printed Circuit Board is 25.00 ZAR.
Below is the graph showing the amount of pulses per second verses the values of resistance and capacitors. This will give the approximate frequency, for more accurate adjustment add a trimpot in the allocated space to set up with a frequency counter.
