Discussion Overview
The discussion centers on the issue of an NE555 timer being inadvertently triggered upon power-on in a circuit designed to activate a solenoid driver. Participants explore potential causes and solutions related to the triggering mechanism and circuit design.
Discussion Character
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- Mike Phan describes the problem of the NE555 timer triggering unexpectedly when power is turned on and questions the nature of the signal causing this.
- One participant asks for the complete circuit and inquires about the configuration of pin 4.
- Another participant confirms that pin 4 is a reset pin and suggests connecting it to Vcc through a resistor and to ground through a capacitor to hold the timer in a reset state briefly at power-up.
- Mike Phan mentions using a 10M ohm resistor and a 4.7uF capacitor but still experiences the triggering issue, questioning the appropriateness of these values.
- A participant points out that the RC time constant with those values would be 47 seconds, suggesting it might be too long for the intended application.
- Another participant discusses the implications of using a 10M ohm resistor with a bipolar NE555, noting that it may not be suitable due to input bias current considerations, and contrasts this with a CMOS version of the timer.
- One suggestion is made to hold the trigger pin high with a 10k ohm resistor to mitigate sensitivity to stray pulses during power-up.
- Mike Phan acknowledges the suggestions but indicates that the issue has been resolved already.
Areas of Agreement / Disagreement
Participants express various viewpoints on the appropriate resistor and capacitor values, as well as the configuration of the reset pin. There is no consensus on a single solution, and the discussion includes multiple competing ideas and approaches.
Contextual Notes
Limitations include the lack of a complete circuit diagram and specific details on the NE555 variant being used, which may affect the applicability of the suggestions made.