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#Goal

- Update an existing NE555 pulse-conditioning circuit to operate at 9 V DC, accept a latching trigger input, and produce a 40 ms active-low output pulse suitable for driving an analog switch.

#Implementation plan

1. **Update Power Supply and System Properties**

1. Change the project operating voltage from 5 V to 9 V and update decoupling components accordingly.

2. Verify that U1 (NE555 timer) and supporting components are rated for 9 V operation.

2. **Modify Trigger Input for Latching Behavior**

1. Rework the trigger conditioning network so that a latching input signal reliably initiates a single pulse event.

2. Integrate a mechanism (e.g., a transistor latch or an RC network combined with diode steering) to ensure that the trigger condition holds until the monostable cycle begins and then resets.

3. **Adjust Monostable Timing Network for 40 ms Pulse**

1. Recalculate and select new values for the resistor and capacitor in the timing network to achieve a pulse duration of 40 ms (targeting a product of 1.1*R*C ≈ 40 ms).

2. Replace or adjust the components labeled on the TIMING net accordingly.

4. **Configure Output Stage for Active-Low Behavior**

1. Modify the output stage so that the 555 timer produces an active-low pulse (logic low for 40 ms) to interface with the analog switch.

2. Possibly add an inverter stage or alter the load configuration to achieve the active-low output if the 555’s native output is not compatible.

5. **Documentation and Schematic Update**

1. Update schematic labels (PULSE_IN, PULSE_OUT, CTRL_REF, TIMING) to reflect the revised functionality.

2. Document the changes to component values and circuit functionality in the project notes.

#Success criteria

- The circuit operates from a 9 V DC supply with appropriate decoupling.

- A latching trigger input reliably initiates a single 40 ms output pulse.

- The monostable network produces an output that is active-low for 40 ms, suitable for driving the analog switch.

- All modifications are annotated and integrated into the project schematic.

nets {

net +5V = U1:VCC, R1:P1, C2:P1, R2:P1, U1:R;

net GND = C4:P2, R4 P2 - C4 P2:GND, GND:GND, R4:P2, R3:P1, C3:P2, U1:GND, C2:P2, R5:P2, C1:P2;

net TRIG_NODE = R3:P2, C4:P1, U1:TR, R2:P2;

net PULSE_IN = R4:P1;

net PULSE_OUT = U1:Q, R5:P1;

net CTRL_REF = C3:P1, U1:CV;

net TIMING = R1:P2, U1:DIS, U1:THR, C1:P1;

}

Set Operating Voltage to "9V"

Added 2x Generic Resistor as R6, R7 (Pins: P2, P1)

Added 1x CD4066BPWR as U2 (Pins: CONTROL_B, VSS, SIG_D_IN/OUT, SIG_D_OUT/IN, VDD, SIG_C_IN/OUT, CONTROL_C, SIG_C_OUT/IN, SIG_A_OUT/IN, CONTROL_A, SIG_B_OUT/IN, SIG_A_IN/OUT, SIG_B_IN/OUT, CONTROL_D)