BeginnerTimers & Logic
Four-Input XOR Parity Panel
Build a four-switch trainer that lights when an odd number of inputs are high, demonstrating XOR parity.
Parts from the database
- SN74HC86N × 1Four XOR gates
Other supplies
- breadboardCommon build supply
- 5 V supplyCommon build supply
- four switchesCommon build supply
- four 10 kΩ pull-downsCommon 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 +5 V and pin 7 ground; add bypass capacitor. Each switch connects an input to +5 V, with 10 kΩ from input to ground.
- Cascade XOR gate 1 pins 1/2→3, gate 2 pins 4/5→6; feed pins 3 and 6 into gate 3 pins 9/10, output pin 8.
- Connect output pin 8 through 1 kΩ and an LED to ground. Tie unused input pins 12/13 low; leave output pin 11 open.
Build steps
- With all switches low, verify output low.
- Flip switches one by one; output is high for one or three high inputs.
- Test all 16 combinations and record the parity table.
- Two or four highs produce an even-parity low.
Software and firmware setup
This is a hardware-only circuit; no firmware is required.
Test your build
The LED indicates odd parity: on for an odd count of high switches, off for an even count.
Troubleshooting
- Output changes while idle: repair pull-downs and unused input ties.
- Wrong table: trace the cascade and gate pins.
- Erratic behavior: shorten wires and bypass the IC.
Safety and limitations
Use 5 V and a series LED resistor; stay within HC gate input/output limits.
Manufacturer and platform documentation
Community Notes for This Project
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