Dual Channel Vehicle Loop Detector

USER MANUAL

Version 1.00

1. INTRODUCTION

The designed detector is specifically tailored for parking and vehicle access control applications, offering a dual channel vehicle loop system. Its main purpose is to detect the presence of vehicles using inductance changes triggered when the vehicles pass over a wire loop that is buried beneath the surface of the road.

To select different modes, one simply needs to adjust the switches located on the front of the unit. This action changes the position of the switches, enabling the desired mode. In order to prevent any interference between the loops connected to the detector, a multiplexing technique is employed for the detector oscillator. This technique ensures that crosstalk is completely eliminated. The switches also provide the flexibility to adjust the loop frequency, sensitivity, and mode settings according to individual preferences.

There are several choices available for configuring the relay when it is first set up. Please create similar content by reorganizing the original text information while making sure that the newly generated content is based on it. Do not use the same conversational style as that produced by ChapGPT, but instead, speak with a completely different language model.

outputs.

At the front of the enclosure, the PD-230 features LED visual outputs, while the rear of the enclosure houses 11 pin connectors with relay change-over contacts. The power LED serves as an indicator of the unit's power status. Below, the channel status LEDs provide information on the presence of a vehicle over the loop and indicate any faults. The Presence relays are designed to be fail-secure and will close in the event of a vehicle detection or loop failure. However, they will not close if there is a power failure.

2. TECHNICAL DATA

3. Switch Setting Selections

3.1 Frequency Switch

The frequency switches are the lower two switches, numbered 1 and 2. There are two frequency selections and are set out as follows:

Loop2 Frequency: SW1 OFF – High, ON – Low

Loop1 Frequency: SW2 OFF – High, ON – Low

The frequency switches allow the loop frequency to be shifted higher or lower depending on the switch position. The frequency of the loop is determined by the loop size, and the frequency of the switch simply causes a frequency shift on the loop.

Where more than one detector is used the detectors must be set-up to ensure that there is no cross-talk (interference) between the detectors. This can be achieved by ensuring that the loops of the two detectors are spaced sufficiently apart ( approximately 1~2 meters between adjacent edges ) and also ensuring that the detectors are set to different frequencies. As a general rule, the detector connected to the inductive loop with the greatest inductance should be set to operate at the lowest frequency. Loop inductance increases as loop size, number of turns in the loop and feeder length increases.

When the switch selection is altered, the frequency of the loop will changes and you must be reset the detector.

3.2 Sensitivity

The sensitivity of the detector allows the detector to be selective as to the change of inductance necessary to produce an output. There are four sensitivity selections and are set as follows:

CH1 SW6 SW5

CH2 SW4 SW3

Off Off - Higher

On Off - High

Off On - Low

On On - Lower

3.3 Automatic Sensitivity Boost

Automatic sensitivity boost is a mode which alters the undetect level of the detector .

This mode is selected by switch No. 7 on the front of the enclosure and is set as follows: -

SW7

Off - Disabled

On - Enabled

Automatic sensitivity boost causes the sensitivity to be boosted to a maximum on detection on the vehicle, and maintained at this level during the presence of the entire vehicle over the loop. When the vehicle departs the loop and detection is lost the sensitivity reverts to the pre-selected level.

3.4 Presence Time

The presence time may be set to permanent presence or to limited presence. In permanent presence mode the detector will continuously compensate for all environmental changes whilst there is a vehicle present over the loop. In limited presence mode there will be a finite time that the detector will remain in detect. This time is dependent on the change of inductance that the vehicle caused. The presence mode is set with switch No. 8 and is set as follows:

SW8

Off - Limited Presence

On - Permanent Presence

3.5 Reset Switch

The detector automatically tunes to the inductive loops connected to it when power is applied, whether on initial installation or after any break in the power supply. Should it be necessary to retune the detector, as may be required after the changing of frequency switch selections or after moving the detector from one installation to another, momentary operation of the RESET switch will initiate to the automatic tuning cycle.

3.6 Internal Link Selection

Dual channel vehicle loop detector is 3 link positions located inside the PD230 which are used to alter the output relay configuration of the detector. The links have been placed inside the unit to avoid incorrect operation due to selection by an unauthorised operator.

4. Front Panel Indicator

While the dual channel vehicle loop detector is tuning, the Channel LED will indicate the “mode” status of the detector.

i) Any Channel output operating in the presence or pulse modes will come on and extinguish when the system is tuned.

ii) When the AB Logic mode is selected, the Channel LEDs will alternatively flash slow and extinguish when the system is tuned.

If a loop fault exists the Channel LED will come on and flash indicating a fault. If the fault is self-healing the detector will continue to operate.

The channel LED will also glow whenever a vehicle is detected passing over the inductive loop.

The Power LED at the top of the unit will remain on to indicate that the unit is powered.

5. INSTALLATION GUIDE

Optimum functioning of the detector module is largely dependent on factors associated with the inductive sensor loop connected to it. These factors include choice of material, loop configuration and correct installation practice. A successful inductive loop vehicle detection system can be achieved bearing the following constraints in mind, and strictly following the installation instructions. The detector must be installed in a convenient weatherproof location as close as possible to the loop.

5.1 Operational Constraints

Crosstalk

When two loop configurations are in close proximity, the magnetic fields of one can overlap and disturb the field of the other. This phenomena, known as crosstalk, can cause false detects and detector lock-up.

Crosstalk between adjacent loops operating from different detector modules can be eliminated by:

1. Careful choice of operating frequency. The closer together the two loops, the further apart the frequencies of operation must be.

2. Separation between adjacent loops. Where possible a minimum spacing of 2 metres between loops should be adhered to.

3. Careful screening of feeder cables if they are routed together with other electric cables. The screen must be earthed at the detector end only.

Reinforcing

The existence of reinforced steel below the road surface has the effect of reducing the inductance, and therefore the sensitivity, of the loop detection system. Hence, where reinforcing exists 2 turns should be added to the normal loop, as referred to in section 5.3. The ideal minimum spacing between the loop and the cable and steel reinforcing is 150mm, although this is not always practically possible. The slot depth should be kept as shallow as possible, taking care that the feeder remains exposed after the sealing compound has been applied.

5.2 Loop and Feeder Specification

The loop and feeder should preferably constitute a single unjoined length of insulated copper conductor, with a minimum rating 15A.

Joints in the loop or feeder are not recommended. Where this is not possible, joints are to be soldered and terminated in a waterproof junction box. This is extremely important for reliable detector performance.

5.3 Sensing Loop Geometry

Sensing loops should, unless site conditions prohibit, be rectangular in shape and should normally be installed with the longest sides at right angle to the direction of traffic movement. These sides should ideally be 1 metre apart. The length of the loop will be determined by the width of the roadway to be monitored. The loop should reach to within 300mm of each edge of the roadway.

In general, loops having a circumference measurement in excess of 10 metres should be installed using two turns of wire, while loops of less than 10 metres in circumference, should have three turns or more. Loops having a circumference measurement less than 6 metres should have four turns. It is good practice at time of installation to construct adjacent loops with alternate three and four turn windings.

5.4 Loop Installation

All permanent loop installations should be installed in the roadway by cutting slots with a masonary cutting disc or similar devise. A 45° crosscut should be made across the loop corners to reduce the chance of damage that can be caused to the loop at right angle corners.

NOMINAL SLOT WIDTH: 4mm

NOMINAL SLOT DEPTH : 30mm TO 50mm

A slot must also be cut from the loop circumference at one corner of the loop to the roadway edge to accommodate the feeder.

A continuous loop and feeder is obtained by leaving a tail long enough to reach the detector before inserting the cable into the loop slot. Once the required number of turns of wire are wound into the slot around the loop circumference, the wire is routed again via the feeder slot to the roadway edge.

A similar length is allowed to reach the detector and these two free ends are twisted together to ensure they remain in close proximity to one another. ( minimum 20 turns per metre ) Maximum recommended feeder length is 100 metres. It should be noted that the loop sensitivity decreases as the feeder length increases, so ideally thefeeder cable should be kept as short as possible.

The loops are sealed using a “quick-set” black epoxy compound or hot bitumen mastic to blend with the roadway surface.

6. CONFIGURATION

6.1 PD-231 Detector CONNECTOR

PIN DESIGNATION

1 Live 120V AC input

2 Neutral ±15% 50/60 Hz

3 Channel 2 Common

4 No Use

5 Channel 1 Common

6 Channel 1 N/O

7 Channel 1 loop Twist

8 Channel 1 loop this pair

9 Channel 2 loop Twist

10 Channel 2 loop this pair

11 Channel 2 N/O

6.2 PD-232 Detector CONNECTOR

PIN DESIGNATION

1 Live 230V AC input

2 Neutral ±15% 50/60 Hz

3 Channel 2 Common

4 No Use

5 Channel 1 Common

6 Channel 1 N/O

7 Channel 1 loop Twist

8 Channel 1 loop this pair

9 Channel 2 loop Twist

10 Channel 2 loop this pair

11 Channel 2 N/O

6.3 PD-234 Detector CONNECTOR

PIN DESIGNATION

1 Live 12-24V input

2 Neutral AC/DC

3 Channel 2 Common

4 No Use

5 Channel 1 Common

6 Channel 1 N/O

7 Channel 1 loop Twist

8 Channel 1 loop this pair

9 Channel 2 loop Twist

10 Channel 2 loop this pair

11 Channel 2 N/O

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