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GATE AUTOMATION UPGRADE - a solar powered gate operator

David G. Ehler

June 1995, Water Operations and Maintenance, Bulletin NO. 172

The Water Resources Research Laboratory (formerly known as the Hydraulics Branch, Division of Research) in the Denver Technical Service Center is active in developing low cost automation products for canal automation. A simple, low cost gate control system for remote sites has recently been developed and field tested in conjunction with the Provo Project Office. In addition to providing conventional telemetry (remote monitoring) of water levels, flows and gate positions; it is now possible to monitor and control gates even at the most remote site. Automatic control of gates is also possible at these sites at a relativly low cost.

To paraphrase Russel Anderson at the Richfield site "It is really a great help to be able to control the canal gates from my home, I want all our canal gates set up this way."

photo Figure 1 - Richfield, Utah

This system provides telemetry and gate operation by using a gate operator with the following operating criteria.

Commercial Gate Operators - A number of commercial gate operators are available. However, these are expensive and often require 3 phase power or additional expense to modify for single phase or DC operation. These systems are too power hungry for battery and/or solar operation.

Low Cost Gate Operators- To overcome these problems a DC gate operator was designed by the Denver office with help from the Provo Project Office. Design requirements included low cost, low power, 12 or 24 volt operation using deep cycle marine type batteries, solar panel battery charging, and suitable for rising stem gates and valves.

The system was designed around a fractional horsepower 24 Volt DC gear motor and an adapter plate used to fasten a gear to the gate hand wheel. A number of gear motors are available in the 12 and 24 volt range rated at 1/15 and 1/8 Horsepower (HP). Typical are the Dayton DC gearmotors available from Grainger and other suppliers. These motors match up well with one or two 12 volt deep cycle batteries and one or two 40 watt solar panels with chargers. The 1/8 HP motors are used for larger gates and higher head submerged gates. 24 volt systems are used for gates with high duty cycles. Figure 2 shows a typical fractional horsepower gear motor. The gate position can be derived from a fabricated string transducer attached to the gate stem. Open and closed limit switches are activated by the gate stem, the limit switches are installed to stop the gates at the maximum and minimum positions. These switches can be adjusted to set operational limits such as minimum flow and gate normal maximum.

photo Figure 2 - Fractional HP Gear motor on prototype

Design of the Gate Drive - Low horsepower DC motors can be used for these applications since most gate movements are small and do not require full cycle or fast operation. The motors are geared to move slowly allowing the use of fractional Horsepower motors. An occasional full cycle operation for canal shutdown or an emergency is possible.

An adapter plate as shown in figure 3 is used to attach a gear to the gate handwheel. It also aligns and centers the gear on the hand wheel. Additionally the adapter provides spacing between the hand wheel and gear for clearance between the chain and handwheel. Figure 4 is a typical rising stem slide gate installation. The gear motor is attached to the gate frame with a bracket that allows adjustment of the chain. Idler sprockets should not be used.

A reversing motor controller is made with two double pole double throw relays. The relays are have 12 or 24 volt coils to match the gate hoist motors and 10 to 15 amp contacts to match the motor ratings. The relays are wired to provide an interlock to stop the motor should both relays activate at the same time. A fuse is installed in the motor circuit as a secondary safety device. The fuse is sized to blow should the motor stall or draw heavy current. This could happen if the gate is jammed with debris, the hoist is jammed, or a limit switch fail. Figure 5 is a schematic of the gate controller. The controller can be driven by outputs from controllers such as the Campbell Scientific CR10 or the Geomation 2300 series.

Equipment List and Cost Estimate -
Equipment and parts for a rising stem gate modification:

      Gear motor 1/15 HP 20 RPM 12 (or 24) Volt DC      $250
      Large sprocket, flat, 72 teeth for handwheel        30
      Small Sprocket, Bushed bore for motor, 10 teeth      7
      Chain                                               25
      Fabricated handwheel adapter plate
      Fabricated Motor bracket
      Fabricated chain/sprocket guard
                                              sub       $312
      Relays, DPDT 12 (or 24) volt coil, 2 each @$25      50
      Inline fuse holder and fuse (with spares)            5
      Limit switches, 2 each @$5                          10
      Position device (string transducer)
      Fabricated limit switch/position device housing
                                              sub       $ 65
 POWER (for a 12 Volt system, double for 24 Volt)
Solar Panel(s) for 12 (or 24) volt 250
Regulator/Charger 45
Battery(s) for 12 (or 24) volt operation 65
sub $360 TOTAL - (Not including fabricated parts and labor) $637


Figure 1 - Richfield, Utah

Figure 2 - Fractional HP Gear motor on prototype

Figure 3 - Adapter Plate (not shown here)

Figure 4 - Typical instalation (not shown here)

Figure 5 - Motor controller schematic (not shown here)

Last Modified: 15 March 1995

Bureau of Reclamation, Department of Interior