The 555 timers I use don't always generate pulses

Thread starter David lopez
Start date May 12, 2019
Tags

electronics

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SUMMARY

The discussion centers on troubleshooting issues with 555 timers that intermittently fail to generate pulses. Key problems identified include the lack of a capacitor connected to pin 5, which should be grounded to reduce noise, and potential wiring errors on the breadboards used. The user reported success with a white breadboard but encountered issues with a grey one, suggesting possible contact problems or defects in the grey breadboard. Participants emphasized the importance of providing circuit diagrams and photos for effective troubleshooting.

PREREQUISITES

Understanding of 555 timer configurations, specifically astable mode.
Familiarity with breadboard wiring and common issues related to contact integrity.
Knowledge of capacitor functions, particularly in noise reduction for timing circuits.
Ability to read and interpret circuit diagrams.

NEXT STEPS

Research proper grounding techniques for 555 timers, focusing on pin 5 connections.
Investigate the differences between various breadboard types and their impact on circuit performance.
Learn about alternative timer ICs, such as the 7555 and TimerBlox from Analog Devices.
Explore methods for diagnosing and repairing breadboard contact issues.

USEFUL FOR

Electronics hobbyists, circuit designers, and anyone troubleshooting 555 timer circuits or working with breadboards in prototyping environments.

May 16, 2019

Baluncore

Science Advisor

2025 Award

Those prototyping boards are susceptible to bent contacts. If a thick wire is used it can open the contacts, then when a thinner wire is used, that contact may be intermittent. Worn contacts may also be a problem as oxide forms on the base metal.

When a circuit does not work, test the contacts by inserting a long link in parallel with the suspect link, use different holes in the same bars.

Look under the board. It is usually possible to remove the base to access the connector bars, remove a bar, clean out the dirt, then carefully bend the spring contacts back into shape.