Plastic heat sealing machine circuit

This device is suitable for heat sealing polyethylene plastic bags, with a power of about 40W and a production cost of 4-7 yuan. It can be used by families, small shops and small manufacturers.
    (1) Circuit principle This circuit has a unique concept and simple design. It can be used to heat and seal plastic materials of different thicknesses at regular intervals
. The circuit is shown in Figure 7-33. VD1 and G form a rectifier and filter circuit to obtain a DC voltage of 300V. Ri and Rz are stepped down to obtain a DC
voltage of 24V, which is used by the timing control circuit . SB1 is closed, relay KA is energized, KA is closed, the voltage is reduced by transformer T, and the electric heating wire is energized; it starts to
heat up.
    At the same time, C2 starts to charge from R3 and RP. As
the electric basket at both ends of C rises, VT begins to conduct, the voltage
rises to a certain level, the voltage regulator tube conducts, and the thyristor VTH
conducts. Due to the conduction of VTH, the relay coil is short-
circuited and loses power, KA is disconnected, the heating wire loses power and stops heating,
completing a scheduled heating process. Adjusting RP can change
the scheduled heating time to adapt to materials of different thicknesses.
    LEDs are directly connected in the relay winding circuit for
working status indication. It lights up when heating and goes out when not heating.
During production, 1A/400V is used for the bidirectional thyristor,
2~3V tube is used for the voltage regulator tube, and 9014 is used for the transistor. Other components are as
shown in the figure. If necessary, make appropriate adjustments as needed.
    (2) Production method: Drill two small holes at the original hole spacing,
then use a steel plate to center the iron core in the middle, place the angle iron
outside the steel plate, and tighten it with screws. On both sides of the angle iron, first place asbestos boards, and use two pieces of surgical boards to cut the outer layer into handles to clamp it. Then use two nails to
clamp it. Finally, connect the capacitor and the iron core with wires and weld them as shown in the figure. , connect the grounding wire to the screw of the angle iron, and then connect it to the three-wire plug and it is ready to
use.
    (3) How to use: Use a fine file (or grindstone) to smooth the long side of the heat sealer to ensure good heat transfer, and then pin the cellophane and
a piece of cloth (thin cloth can be folded into double layers) with thumbtacks. On a flat wooden board, place the polyethylene film bag to be sealed between the cloth and cellophane,
tap the power plug of the heat sealer, and turn on the power for 3 minutes (if you want to shorten the preheating time, you can string a double coupler on the line. Danguan S, as
shown in Figure 7133, turn the switch S to the l position. After reaching the required temperature, turn the switch S back to the 2 position). After the heat sealer is heated, you can hold
the wooden handle to use the heat sealer. The edge of the knife is close to the sealing point of the plastic bag on the cellophane. After about 1 minute, the plastic bag mouth can be bonded. Then quickly remove
the heat sealer, then slowly uncover the cellophane, and the bag mouth will be sealed.