BeginnerTimers & Logic
Schmitt-Trigger Slow Clock
Make a slow RC oscillator with one SN74HC14 gate and use its logic output to blink an LED.
Parts from the database
- SN74HC14N × 1Schmitt-trigger inverter
Other supplies
- breadboardCommon build supply
- regulated 5 V supplyCommon build supply
- 100 kΩ resistorCommon build supply
- 10 µF electrolyticCommon build supply
- LEDCommon build supply
- 1 kΩ resistorCommon build supply
- 100 nF bypass capacitorCommon build supply
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Connections
- DIP-14 pin 14 to +5 V and pin 7 to ground; place 100 nF across them.
- Connect output pin 2 through 100 kΩ back to input pin 1; connect 10 µF from pin 1 to ground, positive at pin 1.
- Connect pin 2 through 1 kΩ to LED anode, LED cathode to ground. Tie every unused HC14 input to a defined logic level.
Build steps
- Check the supply pins and electrolytic polarity.
- Measure pin 2; it should alternate as the capacitor charges and discharges.
- Add the LED and compare rates after changing R or C.
- Keep the timing node short.
Software and firmware setup
This is a hardware-only circuit; no firmware is required.
Test your build
The LED blinks slowly. Rate depends on Schmitt thresholds and component tolerances; this is not a precision clock.
Troubleshooting
- Steady output: check resistor feedback and capacitor-to-ground connections.
- Unstable: shorten the timing lead and place the bypass capacitor at the IC.
- Unexpected behavior: do not leave any HC14 input floating.
Safety and limitations
Operate from 5 V only and disconnect power before changing parts.
Manufacturer and platform documentation
Community Notes for This Project
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