Fish Stunning and LLIormer Project

This usel’ul project is intended used for driving worms out of the ground or stunning fish while in their normal environment. This stupefying effect allows tagging and relocating as the fish float to the surface. It is best to check before trying this in public waters, as many states do not allow “electric fishing” except by those qualified.

The device (see Figure 24-1) must be used with caution as improper use can cause electric shock.

The finished project should have a danger label affixed to it.

Expcct to spend 550 to $100 for this outdoor proj­ect. Most parts arc readily available, and any special­ized parts are obtainable through www. amazingl. com. The parts for this project are listed in Table 24-1

General Description

Fish Stunning and LLIormer Project

As shown in Figure 24-2. this project generates an adjustable 1 to 2 joules of 600-volt pulses at a 30- reps-per-second rate. The output of the circuit is elec­trically floating (no ground reference) to minimize but not totally eliminate a dangerous shock potential. The output leads are intended to be connected to probes or drag chains, as shown in the operating instructions.

The device is housed in a З-inch polyvinyl chloride (PVC) tube with splash-proof plastic end caps. The front cap retains the control panel with power switch (Si), pulse energy pot (R5). light-emitting diode (LED) power on the indicator, and the input power leads. The rear cap has a passage hole for exiting the output leads. This arrangement helps protect the device from moisture but in no way makes the unit submersible.

Circuit Description

The circuit utilizes inductive charging similar to that used in the ignition systems of older automobiles. The primary winding of the transformer Tl current charges through metal-oxide-semiconductor field effect transistor (MOSFET) switch Ql. The current ramps up to a value determined by і = Et/L, where E equals the 12 volts-direct current (VDC) input, L the inductance of the Tl primary, and t the “on” time of switch Ql. The pulse energy is now equal to Li2/2 because it is being controlled by the “on" time as determined by pot R5.

Transformer Tl requires cutting in an air gap nec­essary to store the inductive energy because the core itself would saturate, making Tl useless.

Tinier II is wired as a stable pulse generator with a fixed frequency determined by the total value of pot R5 and trimpot R4, along with timing capacitor C2.

Trimpot R4 is used to set the maximum core charging time range of R5. Resistor R6 and capacitor C5 decouple the operating voltage (Vc) to timer П from the main 12 VDC. LED D4, along with the current — limit resistor, indicate when power switch SI is on.

Construction Steps

To begin assembly, follow these steps:

1. Lay out and identify all parts and pieces, checking them with the parts list. Note that certain parts may sometimes vary in value. This is acceptable as all components are 10 to 20 percent tolerant unless otherwise noted.

2. Create the PBl assembly board at 2Ча X 5 inches from a piece of.1 X Л vector board. Note that it is a good idea to duplicate the placement of the perforated holes as shown in Figures 24-3 and 24-4. This makes placement of the components identical lo what is shown.

3. Assemble the board as shown, inserting the components into the board holes. Proceed from right to left, attempting to obtain the lay­out as shown. Dashed lines indicate connec­tion runs on the underside of the board.

Fish Stunning and LLIormer Project


Note that certain leads of the actual compo­nents will be used for connecting points and circuit runs. Do not cut or trim them at this time. It is best to temporarily fold the leads over to secure the individual parts from falling out of the board holes for now.

4. Rework the Tl transformer as shown in Fig­ure 24-4.

5. Put the frame assembly (FRAME) together, as shown in Figure 24-5. You may want to trial-fit the components before actually fabri­cating.

6. Mount the components to the frame as shown in Figure 24-6, using TYE1 wraps to secure Tl. Note the mounting of Ql, using a thermo pad and nylon screw. The large capacitor Cl is mounted behind the assembly board with the ground side attached to the common ground­ing lug LUG I.

7. Preconnect all the leads as shown in Figure

24- 4. Note that the wires intended for input and output leads are 3 to 4 feet in length. They may be longer or shorter.

8. Check the wiring for any potential shorts, wire bridge shorts, poor solder joints, the correct­ness of the components, and the position and orientation of semiconductors and capacitors.

Fish Stunning and LLIormer Project

Figure 2Ч-Ч Final wiring showing transformer rework

Fish Stunning and LLIormer Project

View side m

You may use these drawings as templates for fabncatmg the frame section Note lo verify hole dimensions for components used.

Figure 24-5 Construction of the frame assembly template

Fish Stunning and LLIormer Project

Figure 24-6 Isometric overall view