Seeking Advice on Proximity Magnetic Switch Use

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Discussion Overview

The discussion revolves around the use of proximity magnetic switches in circuits, specifically concerning the potential for arcing, current surges, and the implications for circuit protection. Participants explore the effects of switching on and off, particularly in relation to different types of loads, such as resistive and inductive components.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Ramone questions whether switching a proximity magnetic switch on and off could cause arcing or current surges that might damage low current circuit components, despite having resistors to limit current.
  • Bob suggests that if the switch is on the primary side of a transformer or inductive device, voltage spikes and arcs can occur. He notes that direct coupling to a capacitor without a current-limiting resistor can lead to current surges.
  • Bob also mentions that using an incandescent lamp can result in surges due to the low resistance of a cold filament, while a pure resistive load is acceptable if it stays within the switch's ratings.
  • Don introduces the concept of "switch bounce," explaining that the mechanical action of closing a switch can cause it to momentarily reopen, potentially affecting fast circuits.
  • Ramone seeks clarification on whether to use a resistor greater than or equal to 10 watts to handle potential arcing or surges and inquires about the use of flashing circuits with LEDs to prevent damage from current surges.

Areas of Agreement / Disagreement

Participants express varying views on the implications of using proximity magnetic switches, with some agreeing that arcing can occur while others focus on the effects of switch bounce. The discussion remains unresolved regarding the best practices for resistor selection and the use of flashing circuits with LEDs.

Contextual Notes

There are limitations in the discussion regarding the specific characteristics of the circuit components, such as the exact ratings of the switch and resistors, as well as the absence of detailed specifications for the flashing circuits mentioned.

ramonegumpert
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Dear Gurus,

I have a doubt about switches.
I have a proximity magnetic switch i used to switch on and off a circuit.
I wonder would there be arching or spikes or current surges when the switch is switched on and off repeatedly ? My circuit has resistors to limit the current. Will switching on and off cause current surges that can damage the low current circuit components? Or is it that the resistors is sufficient to protect the circuit?

Seeking your advice.

sincerely
Ramone
 
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If your switch is on the primary of a transformer or other inductive device, you can get voltage spikes and sometimes arcs. If the switch is directly coupled to a capacitor without a series current-limiting resistor, you can get current surges. If the switch is in series with an incandescent lamp, you can still get a surge due to the low resistance of a cold filament. A pure resistive load is ok as long as it is within the switch's voltage and current rating.
Bob S
 
It really doesn't have anything to do with surge but "switch bounce" can be a problem with analog and digital circuits that are fast enough to see the bounce. When you close a switch, the momentum of the contact coming closed can cause it to reopen/bounce. I've seen switch that will bounce open and closed several times before finally settling down.
 
Dear Bob and Don , thank you so much for giving me advice.

The device to blink is a 10Watts filament bulb.
So, I gather from the forum is that for such a mechanical switch, arcs can occur.
I assume that by arcs (like lightning) implies more current than necessary will flow through the circuit requiring a resistor to protect the circuit.

Should I be using a greater than 10 watts resistor, of say 1 ohm, or just a 10watts or lower resistor, of say 1 ohm to handle the arcing/surge?

If LEDs were used, would using flashing circuits that uses a combination of 555 timers, capacitor ad resistors be able to avoid current surges that could damage the LEDs?

sincerely
Ramone
 
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