Explore NE556 pins, signal names, electrical functions and connection guidance for each package.
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Discharges the external timing capacitor when this channel is LOW.
Connect to the junction of RA and RB.
This is a switching node, not a second push-pull output.
Ends the HIGH interval when the timing node exceeds the upper reference.
Join to 1TRIG and the timing capacitor.
Nominal reference: 2/3 VCC with CONT unmodulated.
Sets the comparator reference for timer 1.
Bypass to ground with 10 nF in the example.
Changing CONT changes both thresholds and the timing equations.
Forces this output LOW and turns on its discharge switch.
Tie to VCC for continuous operation.
Do not leave reset floating; it overrides trigger and threshold.
Timer 1 output, independent of the other channel.
Connect a high-impedance scope or a current-limited LED.
Output swing depends on load; it is not rail-to-rail.
Starts the HIGH interval when the input falls below the lower reference.
Join to 1THRES in the astable example.
Nominal reference: 1/3 VCC. A sustained LOW trigger can hold the output HIGH.
Common return for both channels.
Connect all local ground symbols to supply return.
Starts the HIGH interval when the input falls below the lower reference.
Join to 2THRES in the astable example.
Nominal reference: 1/3 VCC. A sustained LOW trigger can hold the output HIGH.
Timer 2 output, independent of the other channel.
Connect a high-impedance scope or a current-limited LED.
Output swing depends on load; it is not rail-to-rail.
Forces this output LOW and turns on its discharge switch.
Tie to VCC for continuous operation.
Do not leave reset floating; it overrides trigger and threshold.
Sets the comparator reference for timer 2.
Bypass to ground with 10 nF in the example.
Changing CONT changes both thresholds and the timing equations.
Ends the HIGH interval when the timing node exceeds the upper reference.
Join to 2TRIG and the timing capacitor.
Nominal reference: 2/3 VCC with CONT unmodulated.
Discharges the external timing capacitor when this channel is LOW.
Connect to the junction of RA and RB.
This is a switching node, not a second push-pull output.
Positive supply shared by the two timers.
Apply regulated +5 V; place 100 nF directly between pins 14 and 7.
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