In my Make: Electronics book, I can't get one of the experiments/projects to work (all others up till now have have worked for me). It is figure 4-29 on page 168, under the 'Chaining Chips' heading.
You are shown how to connect the output (pin 3) of a 555 to the trigger (pin 2) of another 555. When the output pulse of the first 555 ends, this triggers the next 555 to turn on. When it ends, it triggers the next 555 downstream, and so on. The output of the final 555 is fed back to the trigger on the first 555 to restart the whole process. All 555s are in monostable mode. The output of each 555 is also connected to an LED to make the LEDs light up in sequence.
Here is the schematic from the book. I highlighted the positive and ground 'rails' with red and blue pencil for clarity. I built this circuit on a breadboard, but in a linear rather than circular layout. When power is applied, or when the switch is moved from one position to the other, it only makes some of the LEDs turn on, but no moving sequence.
Any ideas about what I'm doing wrong? Isn't there supposed to be a pullup resistor connecting each #2 pin to the positive rail so that each 555 remains off unless triggered by a low voltage? Thanks for any help.
You are shown how to connect the output (pin 3) of a 555 to the trigger (pin 2) of another 555. When the output pulse of the first 555 ends, this triggers the next 555 to turn on. When it ends, it triggers the next 555 downstream, and so on. The output of the final 555 is fed back to the trigger on the first 555 to restart the whole process. All 555s are in monostable mode. The output of each 555 is also connected to an LED to make the LEDs light up in sequence.
Here is the schematic from the book. I highlighted the positive and ground 'rails' with red and blue pencil for clarity. I built this circuit on a breadboard, but in a linear rather than circular layout. When power is applied, or when the switch is moved from one position to the other, it only makes some of the LEDs turn on, but no moving sequence.
Any ideas about what I'm doing wrong? Isn't there supposed to be a pullup resistor connecting each #2 pin to the positive rail so that each 555 remains off unless triggered by a low voltage? Thanks for any help.
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