Archive for February, 2014|Monthly archive page

Missing the point…..

Thursday, February 27th, 2014

Redundant fire relay

I found this today, a recent install. Maybe we need to make the instructions a little more clear/simple. The installer has used a separate relay to take the fire interface and monitor the fire trip. They have then fed the switched power into the fuse module.

The whole point of the PP8FR is to provide a simple ALL IN ONE interface including fire trip relay and monitoring. The separate relay is NOT NEEDED. See extract below from install notes. I apologise for the IBone photo quality.

PP8FR Fire Trip Setup

Power Port Fire Trip Interface Settings.

What is next for the Power Port Range?

Thursday, February 27th, 2014

The time has come to evaluate the current design of the PP8FR and PP4F against current market needs.

We would greatly appreciate any feed back or new ideas from installers of our Power Port range. If you have any comments or want to make suggestions for new features please feel free to comment on this blog post or use the contact for at jackfuse.com

Security Cable Voltage Drop Part 2 Technical Calculations & Solution

Sunday, February 23rd, 2014

Voltage drop issues in security systems can be avoided with some simple calculations leading to correct cable selection.

Theory
We power electric locks and other devices via sheathed copper cable. This cable has a known resistance per meter and the electric device will require a known current.
The resistance causes the voltage to drop as per Ohms law. Naturally the voltage drop will rise as the cable gets longer. The third factor for calculating the voltage drop is the current required. The formula is V=IR (Voltage = Current X Resistance).
Resistance and current values are usually stated in the equipment data sheets and cable data often also comes with a formula that is essentially Ohms law.

Formula and Calculation
Basically V(drop) = I X R
Where
I = Current required by the end device
R = Total resistance for the cable for the whole run

An example is provided below.
Cable distance = 100m X .03 ohms per meter = 3 ohms per 100m
Lock current draw = 1Amp,
V(drop) = 1Amp X 3 Ohms = 3V

A 3V drop from the 13.8V power supply would be unacceptable.

Solution
Usually as the copper conductor size increases the resistance will drop. So select a larger cable that will provide a voltage drop within operating voltage tolerances of the device at the end of the cable. Be warned that the resistances between cable manufacturers and types can vary. So it is best to check the cable data prior to using a new brand or type.

Cable is relatively cheap compared to labour, so it is a good practice to rough in a slightly larger cable than you think you will need. This will save a costly re-run if the voltage drop proves too much or the current requirement is changed. It also means you don’t have to worry about the V(drop) calculation on every run, just the long or high current ones.

Spot the problem?

Friday, February 21st, 2014

Mag lock mounted wrongMag lock all wrong

Yes that is a sliding door!

This mag lock was installed by a carpenter, it is switched via a cheap hotel style locking system. Obviously this did not work long due to the lock grabbing the armature plate as soon as it slid close to the face. The door would not close and quickly the plate was dislodged. The mag was also packed down with cheap plastic spacers.

An experienced locksmith was called in and paid to install the proper L&Z configuration. The L&Z bracket was supplied with the lock but the original installer obviously did not have a clue.

Thanks to the locksmith (Luke) for the photos. Another reason only qualified and experienced tradesmen should be used.

Security Cable Voltage Drop Part 1 – Explanation and Diagnostics

Friday, February 21st, 2014

Cable voltage drop refers to the lower potential available at the far end of a cable run compared to the potential available at the power supply end. Voltage drop in access control systems is often ignored until it presents a problem and can be difficult to diagnose.

The effect of voltage drop is most often encountered with high current devices such as mag locks at the end of a long cable run. The voltage drop will cause a weak bond and will often cause the bond sense circuit to fail.

A voltage drop fault can be diagnosed by checking the voltage at the lock under load and no load conditions. The no load condition should be very close to the voltage at the power supply. Under load a severe problem will cause a drop of 2 or more volts at the lock while the voltage at the power supply will appear relatively unaffected. The voltage is lost in the cable.

Very occasionally cable damage or a manufacturing fault will cause this problem even on short runs but in the vast majority of cases the long cable run cannot support the required voltage at that current.

This problem is not limited to electric locks; any device with an insufficient cable can be affected. Voltage drop faults are often seen at field door controllers, remote devices and external gates.

In part 2 we will talk about solutions to this problem and some related calculations.