Resistance

Resistance is the measurement of the ability of electrons to move through a material. A copper wire with a large diameter has lower resistance to the flow of electrons than a copper wire with a small diameter. You need to understand resistance because almost every electronics project you do involves a resistor. Resistors have controlled amounts of resistance, which allows you to control the flow of electrons in a circuit.

The force that reduces or stops the flow of current is know as Resistance.

• It opposes voltage
  • Higher Resistance decrease the flow of current
  • Lower Resistance increase the flow of current.
• Resistance is measured in OHMS.
• Represented by the symbol Ω
• Electrical Resistance of a conductor is a measure of how difficult it is to push the charge along the conductor.
• Long thin wires provides more resistance than short thick wires.

The resistance of a material depends on its

• Length
• Cross sectional area (the thickness of the wire).
• The resistivity of the material.
• Copper = low resistance
• Copper cladded aluminium = higher resistance

If there is no resistance in an electric circuit, out batteries would be empty in a very short time.

• This is also called a short circuit. Be very careful. Short circuits generate heat and can cause burns on your hands if you were the cause of the short.. 

Alarm Systems

When alarm cabling is run over a long distance, an increase in resistance occurs, leading to potential issues with the terminating resistors, as well as data transmission issues. The distance limitations are set to ensure optimal signal integrity and reliable transmission of data within the specified parameters. However, when the cable length surpasses these limits, the electrical resistance along the length of the cable rises, causing a drop in the signal strength and potentially disrupting communication between devices. As a result, the terminating resistors may fail to function effectively on Zones, as their performance is designed to work within the specific resistance range. Therefore, it is essential to adhere to the recommended distance limitations, and choose the right cable to maintain a stable and efficient alarm system.

Impact on Zone Circuits

• False alarms or missed triggers due to incorrect voltage readings.
• Fault conditions where the panel may interpret normal wiring as a cut or short circuit.
• Communication errors between sensors and the control panel, disrupting system functionality.

Impact on Power Runs

Zone circuits rely on terminating resistors to help the control panel detect changes in a circuit—whether it’s normal, open, shorted, or triggered. When cables are too long, the resistance increases, weakening signal strength. This can result in unreliable zone behavior, such as:

Power runs supply voltage to detectors, keypads, and modules. However, excessive cable distance leads to higher resistance, causing:

• Voltage drop, where powered devices receive lower-than-expected voltage, potentially causing malfunctions or failure.
• Reduced current flow, limiting the ability to sustain multiple connected devices over long distances.
• Unstable operation of powered components, affecting overall system reliability.

How to Prevent These Issues

To maintain reliable performance, use low-resistance cabling with appropriate gauge thickness for longer distances. Options like using stranded cable or solid cable or using copper cable vs copper cladded aluminuim cable has their applications. Additionally, consider installing local power sources for remote devices rather than relying on excessively long cable runs.

Summary

• Voltage: EMF
  • Causes current to flow in a circuit
  • Measured in Volts
• Current: Movement of electrical charge
  • Flow of electrons through a electronic circuit
  • Measured in Amperes or Amps (A)
• Resistance: Opposition to the flow of electricity in a circuit.
  • Used to control the voltage and current in circuits.
  • Measured in OHMS (Ω)
• Power Volts x Amps flowing in a circuit
  • Measured in Watts