rgatlin Posted November 18, 2004 Report Share Posted November 18, 2004 New member and I need help bad!! I have a design project for class that requires a circuit to produce a 1kHz tone for 2 seconds, off for 45 seconds, on for 2....and so forth continuously. I need to keep it as simple as possible since we are only allowed to use components that are at the school, i.e. no special IC counters. I pretty much have the 1kHz signal covered with a 555 astable timer but I am having trouble with the 2 second on and 45 second off delay times. Can someone point me in the right direction. I am not sure if I need to drive a counter with another 555 or even how to do that. Any help will be greatly appreciated. ??? Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted November 18, 2004 Report Share Posted November 18, 2004 All you need to do is configure the 555 to give you the on time and the off time. This is done by selecting the right external resistors. I'll try and determine what that will be and get back to you.Okay here is the link you wanthttp://www.williamson-labs.com/480_555.htmSo now you have a few pins to handle. Connect 2 to 6. Add two resistors and a capacitor in series. Connect pin 7 between the resistors. Now you have a charge time that is different than the discharge time. By adjusting the resistor values you can get any amount of charge and discharge times. Quote Link to comment Share on other sites More sharing options...
rgatlin Posted November 18, 2004 Author Report Share Posted November 18, 2004 I understand about using the 555 timer for different duty cycles, but I am not sure that I can get 2 seconds high, and 45 seconds low. That seems like a really long delay without using astronomical size resistors and cap. ?? Quote Link to comment Share on other sites More sharing options...
ante Posted November 19, 2004 Report Share Posted November 19, 2004 Why not, a PWM in slow motion can do this? Quote Link to comment Share on other sites More sharing options...
Kevin Weddle Posted November 22, 2004 Report Share Posted November 22, 2004 May I recommend the two inverter oscillator. The output of the first inverter goes to the input of the second inverter through a capacitor. The second inverter will have a resistor across it and a diode across it. Connect the cathode to the output. As soon as the input to the second inverter goes high, you get rapid discharge sending it low. The output is then of course high. When the input is low, the output is still high and the high charges the input after a long while and finally sends the output low. With output low the input is high and you get rapid discharge sending it low. The output is then of course high. Quote Link to comment Share on other sites More sharing options...
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