How to Build a Drop Trap Remote Control

Project Description: This DIY Project shows how to build a “Drop Stand” Radio Remote Control system for remotely dropping a Drop Trap. Drop traps are especially useful for TNR (Trap, Neuter, Release) programs for catching these “impossible” feral cats who refuse to enter a conventional box/live trap.
Benefits: Prior to a radio remote control option, drop traps were controlled (dropped) using a support stick and a string/rope.

Some of the disadvantages are: (1) the trapper must be reasonably close to the drop trap, (2) the trapper must be nearly perpendicular to the front of the drop trap, and (3) there must be a debris-free path for the release string.

Using radio control, the trapper can be in any “hide” location, including inside a building or vehicle, within about 300 feet of the drop trap, with the radio controlled “Drop Stand” replacing the support stick, and the radio transmitter/receiver replacing the string.

Every effort has been made to make the remote easy to construct and to minimize the materials. The cost of materials is around $30. Cost will be affected by the materials the builder has on hand suitable to the task. The remote can be constructed in just a few hours.

Click here for printable drawings of the plans (pdf).

1 Radio Controlled Relay
1 GALAXY AC-1 Door Lock Actuator
1 8 AA Battery Holder
8 AA Alkaline Batteries
1 Cap Screw 3/8” x16NC x 3”
1 3/8x16 Nut
1 9v Battery Snap Connector
1 1"x2"x8' Furring Strip
8 3d 1-1/4" Nails
6 #6x1" Round Head Wood Screws
3 #4x1/2" Flat Head Wood Screws
2 1-1/2" Nails
1 3/4" 10-32 Machine Screw
1 10-32 Nut
1 #6 Flat Washer
1 Screw Eye #212 or approximately 7/8” long.
1 Wire Coat Hanger
1’ 22AWG 2 Conductor Alarm Wire
3/16” Wood Dowel
Electrical Tape
40 Grit Sandpaper

The battery holder, batteries and battery snap connector are available from Radio Shack. The wood, hardware, sandpaper and wire can be purchased from Lowe’s or Home Depot. Select a furring strip that is relatively straight and clean. Hardware may be available from Ace Hardware by the piece vs. bagged. The coat hanger should be obtainable from your closet. The batteries can also be purchased here.

3/8" Drill Bit
5/32" Drill Bit
Wood Saw
Slot Head Screwdriver
Phillips Head Screwdriver No.01 Phillips Head Screwdriver for receiver terminal screws
No.00 Phillips Head Screwdriver for changing transmitter battery
(The above two items are included in the General No. 744 4-in-1 Mini Pocket Screwdriver, Home Depot $1.99)
Measuring Tool

Tools – Optional:
Drill Press
Metal File
Soldering Iron, Solder (rosin core)

The photo shows the radio control transmitter, the receiver circuit board, and the receiver's case. The transmitter is the keychain fob type and has a telescoping antenna and a cover that slides over the buttons to eliminate the possibly of inadvertently triggering the trap.

I found the translation from Chinese to English in the manual to be difficult to understand. What follows are hopefully more helpful instructions on how to pair the receiver to the transmitter (the receiver must be trained to recognize the transmitter's code; the operation is called "pairing".)

1. Remove the receiver circuit board from the plastic case.(See Note below)
2. Connect the wires from the battery connector to the receiver board as shown in the system wiring section below.
3. Insert 8 AA Alkaline batteries into the battery holder.
4. Apply power to the receiver by connecting the snap connector to the battery pack.
5. Press the “learning” button on the receiver board until the LED remains on. Hold the button until the LED goes off then flashes 1 time. Release the button. This sets the relay mode to ON when the transmitter button is pressed and OFF when it is released.
6. Next, press the receiver button again until the LED remains on, then release the button and press the “A” button on the transmitter. This pairs the receiver to the transmitter.
7: Test the system. After pairing, a click from the relay should be heard when the transmitter “A” button is pressed.

Note: I thought the case was difficult to separate. I used a utility blade inserted between the cover and back at the sides to pry the pieces apart at the corners. Also the “learning” button extends through the cover through a hole. I had problems when reassembling the unit with getting the button back through the hole correctly. If the button is not properly located the cover will close the switch and the unit will not operate. I don’t know why you need access to the button when the cover is on because you need to see the LED when using the button. I cut the tip of the button off with wire cutters to resolve this.

The transmitter uses a 23A 12v battery. A spare should be kept on hand.

Cut the furring strip to the following lengths:
1 18” piece for the swing arm.
1 14” piece for the base.
1 12 ˝ “ piece for the cross piece.
2 12” pieces for the arm supports.
1 6 ˝” piece for the lever support.
3 1 3/8” (or to the width of the cross piece) pieces , 2 for the feet and 1 for the brace.

Drill one 3/8” hole in the Swing Arm, 5” from the end of, centered on the piece.
Drill one 3/8” hole in each of the Arm Supports, 11-1/2” from the bottom end, centered.
Drill one 5/32” hole in each of the Arm Supports, 1/2” from the bottom end, centered.
Drill one 5/32” hole in the Cross Piece, 3/8” from the rear edge and centered on the length.
Drill two 5/32” holes in the Cross Piece, 3/8” from the rear edge and 1/4” from each end.
Drill one 5/32” hole in the Lever Support, 3/8” from one side and 1-7/8” from the bottom edge.
Drill one 5/32” hole in the top of the lever support for the antenna support (see picture and description further down on the website).
Sand edges and ends smooth

Cut the long length from a wire coat hanger.
Bend one end of the wire around the 3/8” bolt about 3” from the end and cut the “tail” as shown.
Make a right angle bend from the other end, 8-1/4” from the end with the loop.

Attach one Arm Support to the end of the Base using one #6x1” wood screw. Nail the Arm Support to the Base, 5/8” above the screw, using one 1-1/4” nail (to keep the pieces from rotating).

Assemble the Swing Arm to the Arm Supports for alignment using the 3/8” bolt and nut.
Screw and nail the second Arm Support to the Base.
Insert the 1-3/8” brace block between the Arm Supports, with its top 6” above the bottom of the base, using 1-1/4” nails.
Check that the Swing Arm rotates freely. If not, remove it and sand the arm until it moves freely.

Attach the Cross Piece to the Base, centered, using one #6x1” screw and one 1-1/4” nail.
Attach the two Feet to the ends of the Cross piece, using one #6x1” screw and one 1-1/4” nail for each Foot.

From one side of the actuator mounting bracket, make cuts to the top and bottom of the first slot using a hacksaw.
Cut the bracket to a length of 4-1/4”. The bottom slot will be open ended.
File the cut edges if desired.
Drill a 5/32” hole, 1-3/16” from the top and 3/16” from the front side of the bracket (centered in the web between the slots).
This is the Lever for the remote.

Cut a 1/8” slot in top of the Lever Support 3/8”from the side and 3/8” deep.

Bend the Lever at the top of the third slot and the top of the fourth slot so the end that connects to the actuator is set out by 3/8” (i.e., clears the Lever Support by 3/8”). If a vise is not available, the best way I found to do this is by grasping the lever with pliers and bending it against the work bench.

Attach the Lever Arm to the Lever Support as shown, using one #4 x 1/2” flat head wood screw and #6 flat washer.
Place the flat washer between the Lever and the wood support.
The mounting screw should be directly below the center of the slot in the support.
The top of the Lever should be flush to the top of the support.

Position the Lever Support so that the center line of the Lever Support slot is aligned with the center line of the Base.
Attach the Lever Support to the Cross Piece using one #6 x 1” wood screw and one 1-1/4” nail, as shown.

If weatherproofing is desired paint the wood.

Insert the 10-32 x 3/4” machine screw through the hole in the tip of the Actuator arm, and secure with the 10-32 nut.
Mount the Actuator to the Cross Piece, using two 1-1/2” nails, aligned so that the screw end engages the slot in the Lever, and the Lever is vertical when the Actuator arm is fully extended.

On some Actuators (i.e., Aapex), the plastic tip of the Actuator shaft rotates freely, and must be constrained to keep the screw from disengaging from the Lever slot. A drop of Super Glue on the rotating joint will solve this problem.

Attach the Screw Eye to the bottom of the long side of the Swing Arm, 1/4” from the end.
Insert the right-angle-bent end of the Trigger Wire through the Screw Eye and bend it around the Screw Eye.
Cut the “tail” as shown.

Cut the red extension wire to 4 1/2”. Strip the insulation, 1/2” on one end and 1/4” on the other.
Cut the black extension wire into two 4 ˝” pieces. Strip the insulation 1/2” on one end and 1/4” on the other.
Strip the insulation on the other piece 1/4” on each end. (This will be used as the receiver jumper wire.)

Cut off the connectors on the Actuator wires and strip the insulation 1/2”.
Connect the red (positive) wire to the green actuator wire by twisting the ends together and taping the splice.
Connect the black extension wire with the ˝” end stripped to the black actuator wire by twisting the ends together and taping the splice.
If a soldering iron & solder are available, solder the connections, then tape.

Twist together the ends of the red extension wire and the red battery connector wire.
Twist together the ends of the black jumper wire and the black battery connector wire.
Insert the twisted ends into the power input terminal block, as shown, and tighten the screws.
Insert the other end of the jumper wire into the relay terminal block and tighten the screw.
Connect the free end of the black extension wire into the other side of the relay terminal block, and tighten the screw.

Drill a 5/32” hole in the top of the Lever Support for the Antenna Support. Taper the end of a 5”x 3/16” wood dowel with sandpaper and force fit it in the hole. Another option is to drill a 3/16” hole and glue the dowel in place.
A 3/16” dowel is shown in the interest of economy and tools needed but for durability it is recommended a 3/8” dowel be used.

Assemble the receiver and mount to the back of the Lever Support using two #4 x 1/2” screws.
Install batteries in the battery holder, and tape to the Cross Piece, with the snaps facing the center, as shown.
Route the Receiver’s antenna up the support and fasten with electrical tape.
Tape the Actuator wiring to the Cross Piece, as shown.
Tape the opening in the Receiver’s cover to help protect from rain.
Note: the system is turned ON/OFF by unsnapping the snap connector on the battery holder.
Draw a line 1-1/2” from the short end of the Swing Arm. This will be the contact point for the front edge of your Drop Trap.
A rubber band can be used to hold the Trigger Wire in place when transporting.

Manually pull out the Actuator’s shaft.
Turn on the system by connecting the battery snap-connector to the battery holder.
Press the trigger button on the key fob transmitter.
The Actuator shaft should withdraw.
Release the transmitter button.
If it doesn’t work, insure the transmitter and receiver are paired properly and recheck the wiring.

Insert the Trigger Wire’s loop into the Lever Support slot, and manually pull out the Actuator’s shaft to engage the lever.
Place the drop trap on the end of the Swing Arm.
Turn on the system by connecting the battery snap-connector to the battery holder.
Press the trigger button on the key fob transmitter.
The Actuator shaft should withdraw, releasing the Swing Arm.
Reset and repeat the test at a range of at least 200 feet.
Using fresh AA Alkaline batteries, 130 hours of operating time can be expected with the indicator light described below. Battery life can be extended if the Indicator is not used. Under most circumstances changing the batteries every 2 to 3 months should keep the remote operating. Those who do not use the remote frequently would need to change the batteries less often. A meter (Harbor Fright Item 92020 $7.99) can be used to monitor the battery voltage by placing the probes on the snap connector contacts. The batteries should be replaced when the voltage reaches 10v. The transmitter battery should not need to be replaced for several months.


Option 1: Add a switch and indicator light.

For convenience, a switch and indicator light can be added by drilling ˝” and 9/32” mounting holes in a 3”x1”x1/8” piece of wood and gluing it to the lever support.
SPDT Toggle Switch #275-0603 from Radio Shack.
Red LED Assembly #276-0270 from Radio Shack.
Note: Requires soldering iron and solder.
Click here for wiring diagram (pdf).

Option 2: Washer alternative to coat hanger trigger wire.

Alterative to using a wire, 30lb fishing line tied to a washer can be used to hold the swing arm.

Option 3: Battery alternatives:

Instead of 1.5v alkaline AA batteries, eight 1.2v rechargeable batteries may be used though they do not provide a full 12v. Using ten rechargeable AA batteries will provide 12v and require less recharging.
Ten AA Battery Holder
AA battery charger required.

Instead of using AA batteries, a Sealed Lead Acid battery can be used.
Batteries Plus
Terminal connectors, 0.187" fem, crimp (2 ea).
12V charger required.

Option 4: Using alligator clip to secure trigger wire:

An alligator clip can be used instead of a rubber band to retain the trigger wire.

Option 5: Stabilized base assembly:

A trapper added braces to his remote to increase stability with his large, heavy trap.

I would like to offer recognition to Mason at TNR Tech for his assistance in developing this design and for the drawings of the plans.

Please e-mail me with any questions or suggestions. Feedback on your build experience will be appreciated.

Jim Mayes