Pull down button on Port B

[MOUNTAIN747]

Using weak pullups on port B of 16f1936. A button to ground will cause an interrupt on IOCBN.
Question: should I use a low value resistor in line with this pull down button?

Wayne

[richard]

if your query is to do with ameliorating effect of debounce capacitor

google ai says

effect of debounce capacitor on contact life


Adding a debounce capacitor can both extend and shorten switch contact life, depending on its circuit placement and whether it is used with a current-limiting resistor.
1. Protection Against Arcing (Positive Effect)
When a switch opens, especially with inductive loads (like motors or relays), a high-voltage spike can occur, causing an electrical arc that erodes the contacts.
Arc Suppression: A capacitor placed across the switch contacts acts as a temporary short, absorbing the energy that would otherwise cause a spark.
Longevity: By quickly quenching the arc, the capacitor reduces material transfer (erosion) and prevents contacts from "welding" together, significantly extending electrical life.
2. High Inrush Current (Negative Effect)
If a capacitor is placed directly across the switch without a series resistor, it can damage the contacts during closure.
Current Spikes: When the switch closes, the capacitor discharges nearly instantaneously. This creates a massive surge of current—potentially hundreds of amperes for a few nanoseconds—which can cause a brief but severe arc or even weld the contacts shut.
Contact Erosion: For sensitive switches like reed relays, this tiny but intense arc can rapidly erode the contact area and shorten their lifespan.
3. Best Practice: The RC Snubber
To balance these effects, engineers typically use an RC network (a resistor and capacitor in series) rather than just a capacitor.
The Resistor's Role: It limits the discharge current when the switch closes, protecting the contacts from inrush spikes.
The Capacitor's Role: It still provides the necessary dV/dt limiting to prevent arcing when the switch opens.
Result: Properly sized RC components ensure the longest possible contact life by mitigating both opening-arc erosion and closing-surge welding.