The 555 timers I use don't always generate pulses

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Discussion Overview

The discussion revolves around issues with 555 timers not consistently generating pulses in a circuit set up in astable mode. Participants explore potential causes related to circuit construction, component connections, and the use of breadboards.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants suggest that grounding pin 5 with a capacitor is necessary for proper operation, while others confirm this approach.
  • There is a discussion about the importance of connecting pin 4 (Not_Reset) to Vcc, which should also connect to pin 8.
  • One participant explains that pin 5 is connected to a voltage divider inside the 555 timer, and a capacitor helps reduce noise for more accurate timing.
  • Another participant reports that using a 0.1μf polyester capacitor on pin 5 did not resolve the issue, raising questions about the capacitor's functionality.
  • Participants emphasize the need for a circuit diagram and photos of the construction to diagnose the problem effectively.
  • There is a mention of the 555 timer's age and the availability of newer, better alternatives, but some argue that the 555 is still useful for certain applications.
  • One participant notes that the circuit worked on a different breadboard, prompting inquiries about the differences between the two breadboards used.
  • Concerns are raised about potential wiring errors and the quality of the breadboards, including issues with bent contacts and worn connectors.

Areas of Agreement / Disagreement

Participants express a mix of agreement on some technical aspects, such as the need for proper connections and the use of capacitors, but there is no consensus on the root cause of the issue or whether it is a wiring error. The discussion remains unresolved as participants continue to seek more information.

Contextual Notes

Limitations include the lack of a detailed circuit diagram and photos of the actual circuit setup, which are necessary for accurate troubleshooting. The discussion also highlights the variability in breadboard quality and potential issues with component connections.

  • #31
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.
 

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