DIABLO DML-9LP, DMP-9LP Mini Loop Kit Installation Guide
- September 19, 2024
- Diablo
Table of Contents
Installation Guide
Introduction
The Diablo “Mini-Loop” is intended to be buried beneath the roadway surface
and connected, via lead-in cable, to the Diablo DML-9LP Detector. Installation
costs may be significantly less than those for conventional loops, because
only single, straight 1/4-in. saw cuts need to be made and a 1-in. diameter
hole drilled about 20 inches deep. Also resulting is the opportunity for
greatly increased service life due to the reduced exposure to hazards such as
road traffic, pavement movement, pavement deterioration, and roadwork.
The fact that the “Mini-Loop” is not installed in the pavement and that the
lead-in is very durable allows the “Mini-Loop” to be used in situations such
as cobblestone pavements, poor pavements, dirt/gravel roads, and bridge decks.
Minimal intrusion into good pavements is another benefit.
The area of detection provided by a Mini-Loop is smaller than that provided by
a 6-ft. X 6-ft. loop and may be considered a point detector. This
characteristic allows separation of closely spaced vehicles, very good
resistance to detecting vehicles or other moving objects adjacent to the
installed location, and total immunity to “crosstalk” problems.
The “Mini-Loop” in combination with the DML-9LP is ideally suited for
detecting the passage of moving vehicles (moving at 1 mph or faster). The
“Mini-Loop” is not recommended for detecting slow moving or stationary
vehicles.
Basic Installation Guide
Installation is straightforward. A 1-in. diameter hole (18-in to 24-in. deep)
is drilled for the “Mini Loop”. A shallow, 1/4-in. saw cut from the hole to
the edge of the road provides a path for the lead-in wire. The “Mini-Loop”
with lead-in is inserted into the hole and the hole is filled with dry sand.
Detector Loop Sealant material is then used to fill the slot and top portion
of the hole.
It is important that the “Mini-Loop” be installed in a vertical position and
that the vertical position of the “Mini-Loop” be maintained. Under some soil
conditions, installation can be further simplified by installing the Mini-Loop
inside a length of PVC pipe (not steel pipe) with an interior diameter of
about 1 inch. In this case, the hole must be slightly larger than the outside
diameter of the PVC pipe, typically 1-5/8-in. or less. After insertion of the
PVC pipe and Mini-Loop, all cavities are back-filled with fine, dry sand and
the installation completed in the normal manner.
Detection Area
With most vehicles, detection will start at approximately the front bumper and
end at approximately the rear bumper. Oddly shaped vehicles such as bicycles
and trailers may appear shorter to the Mini-Loop than their actual length. For
example, some bicycles detect only for a short period of time near the center
of the bicycle. Aluminum or fiberglass trailers will likely detect only for a
short period of time around the axle and suspension.
These characteristics are very similar to those of a 6-ft. X 6-ft. loop. The
primary difference is that the Mini-Loop in itself is only a point rather than
a 36 square foot area. This allows detection of closely spaced vehicles. It
also places a new limit on maximum vehicle speed to obtain vehicle detection.
Installation Steps
Installation follows these basic steps:
1. Installation Planning
To fully understand the functionality of this product re-read the Basic
Installation Guide portion of this manual.
2. Hole Boring and Saw Cutting
Typically a 1-in. diameter hole is bored to a depth several inches deeper
than final placement to allow for debris in the bottom of the hole. If the
soil is such that the hole walls may collapse, it is suggested that a length
of PVC pipe (plumbing or electrical) be used to line the hole. This will
ensure the Mini-Loop is mounted in a vertical position. It is imperative that
the Mini-Loop unit be mounted in a vertical position and that its position is
stable. When a liner is used, the bored hole must then be somewhat larger than
the pipe outside diameter. Measure the pipe. Plumbing pipe is different from
electrical pipe. Plumbing PVC pipe will probably be 1-1/16-in. diameter and
electrical PVC pipe will probably be 1-5/32-in. diameter.
After boring the hole (and inserting PVC tube, if used), measure the hole
depth to ensure sufficient depth for the Mini-Loop unit to be installed.
A 1/4-in. wide saw cut is then made from the road edge to the hole in the
normal manner as for loops. The cut can be shallower than for loop leads,
because the cable is only .19-in. diameter. If more convenient, saw cuts may
be made before drilling hole for the Mini-Loop units.
Typical Mini-Loop Buried Installation
3. Mini-Loop and Cable Placement
Before inserting the Mini-Loop unit into its hole, it is suggested that a
ring of colored electrical tape be placed on the cable, so that the top of the
tape will line up with the bottom of the saw cut when the bottom of the Mini-
Loop unit is at the correct depth. Insert the Mini-Loop unit and lead-in
cable.
4. Resistance Checks
As a last check before beginning permanent installation, resistance checks
should be made. All Mini-Loop units are fully checked at the factory. However,
it is possible a unit could have been inadvertently damaged during
installation. Such damage will usually be uncovered by a resistance check
using an ohmmeter. Anticipated readings are: .5 ohms nominal per unit and 3.2
ohms per 100 ft. of lead-in cable.
5. Backfilling and Saw Cut Sealing
Fine, dry sand, such as sandblasting sand, works well for filling the hole in
which the Mini-Loop unit is installed. If PVC pipe sleeves were used, fill any
excess area around the sleeve also. It will probably work best to fill the
tube first. Pour some sand over the unit. Then slowly lift the unit until the
depth marking tape aligns with the bottom of the saw cut. Release the unit. If
it goes back down, add more sand and repeat. After stabilizing the Mini-Loop
unit depth, fully fill the hole to the bottom of the saw cut, also filling
around the PVC tube sleeve if used. Complete the installation by filling the
saw cut and hole tops with a quality detector loop sealant.
6. Splice lead-in cable if needed
Connections from the “Mini-Loop” lead-in to the home-run cable are made using
an #18 AWG shielded cable with a tough, highdensity polyethylene jacket. This
protects the cable and system from factors that might degrade and impede
system performance.
This cable uses twisted wires (not twisted pairs) to reject magnetic field
induced noise.
7. Connection to DML-9LP Detector Unit
The connector is a removable 7-pin terminal block. Pin assignments are shown
below – from left to right:
- Relay (NC) (opens for detect)
- Relay Common
- Relay (NO) (closes for detect)
- Power Common
- Power in (10 to 30 Volts AC or +DC)
- Mini-Loop
- Mini-Loop
The Detector and Mini-Loop combinations small size and lack of any switches or
dials, becomes the industry’s first solar friendly “Plug-and-Play” Mini-Loop.
Visit our website at diablocontrols.com for the
most current information on all of our products. Specifications are subject to
change to reflect improvements and upgrades.
Mini-Loop Installation_DMP-9LP_2024 09 04
1497 CR 2178
Greenville, TX 75402
866-395-6677 Ext 105
diablocontrols.com
sales@diablocontrols.com
Documents / Resources
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DIABLO DML-9LP, DMP-9LP Mini Loop
Kit
[pdf] Installation Guide
DML-9LP, DMP-9LP, DML-9LP DMP-9LP Mini Loop Kit, DML-9LP DMP-9LP, Mini Loop
Kit, Loop Kit, Kit
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References
- Diablo Controls - The Experts In Access, Traffic And Parking Control Devices
- Diablo Controls - The Experts In Access, Traffic And Parking Control Devices
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