Simple timing socket circuit making

This simple timing socket can time the final stage of trickle current floating charge of the charger. When the trickle current floating charge reaches the set value, the smart timing socket automatically cuts off the charger and its own AC power supply to successfully complete the charging without manual power off.

1. Circuit composition and principle of simple timing socket

1. Circuit composition of simple timing socket

The circuit of the simple timing socket is shown in the figure below. It consists of four parts: AC power switch K1, electromagnetic unhooking coil drive circuit of AC power switch K1, timing circuit, and DC power circuit. The components of each part are as follows:

AC power switch K1: It is composed of the AC switch with electromagnetic release mechanism of KDC-A01-06Y type commonly used in color TV sets.

The electromagnetic unhooking coil driving circuit of the AC power switch K1 is composed of transistors Q1, Q2, resistor R1 and capacitor C5.

Timing circuit: It consists of a small quartz alarm with a timing sounding function, a plug P1 for introducing a timing start control signal, a jack J1 for leading out a timing start control signal, a resistor R2 and a timing start control transistor 03.

DC power supply circuit: First, the +12V DC power supply is composed of power transformer T, bridge rectifier diodes D3-D6, filter capacitors C1, C2, and three-terminal voltage regulator integrated circuit ICI. Then, the +12V DC power supply working indication circuit is composed of resistor R4 and LED2. Finally, R3, D2LED3, C3, C4, and transistor 04 form a quartz small alarm clock 2.1V circuit.

2. Working Principle

See the figure below, plug in the power plug, press the AC power switch K1 button, and connect the 220V AC power supply.

The 220V AC power supply is stepped down by the 14V power transformer T, rectified by the bridge rectifier circuit, filtered by the filter capacitor C1, stabilized by the three-terminal voltage regulator IC1, and filtered by the filter capacitor C2 to generate a stable +12V DC power supply. The +12V is output in three ways: ① It is added to LED2 through R4 as a +12V DC power supply working indication. ② It is stabilized by R3, D2, and LED3 in series and filtered by C3 and added to the base of the voltage regulator Q4 so that Q4 stabilizes the +12V to 2.1V and outputs it from the emitter of Q4. The 2.1V is filtered by C4 and added to the positive and negative poles of the quartz alarm clock power supply to provide it with DC power. One tip: 2.1V is a bit high, but the quartz alarm clock does not change its running time because it has a quartz crystal oscillator frequency lock. ③ It is added to the electromagnetic decoupling coil of the switch K1.

The 220V AC power is added to the charger through the timing socket. When the charger has not yet entered the floating charge state, the red light LED1 of the charger will light up. The 2V voltage across LED1 is added to the base of Q3 through the jack J1, plug P1, and resistor R2, making Q3 saturated and turned on, and the base of the 2.1V voltage regulator Q4 is short-circuited to the ground, and the voltage regulator Q4 is cut off. The quartz alarm clock has no DC power supply and does not work. When the charger enters the trickle current floating charging stage, the voltage across the red diode LED1 of the charger becomes zero and goes out (the green diode of the charger lights up). At this time, Q3 is also cut off due to the zero voltage at the base, and the power regulator Q4 is normally turned on to output 2.1V DC power. The quartz alarm clock is powered on and starts timing. When the timing reaches the preset value, the quartz alarm clock outputs a low-level audio pulse signal to the base of Q2. The low-level audio pulse signal is amplified and rectified by Q2 and then filtered by capacitor C1 to output a DC voltage, making Q1 saturated and turned on. The electromagnetic unhooking coil of switch K1 is powered on to generate magnetic force, which causes the switch button to unhook and trip, disconnecting the AC power supply and automatically ending charging.

2. Component Selection

The selection of each component is as marked on the circuit schematic: Q1, Q3, Q4 use $8050 transistors, Q2 uses S8550 transistors, IC1 uses LM7812, D1 uses IN4148 diodes, D2~D6 use IN4007 diodes, LED1 is the red charging diode of the charger itself, and no preparation is required. LED2 uses an ordinary red light-emitting diode. LED3 uses an ordinary green light-emitting diode, R1 uses a 2k ordinary resistor. R2 uses a 10k ordinary resistor, R3 and R4 use 1k ordinary resistors, and switch K1 uses KDC-A01-06Y type. P1 and J1 use DC power plugs and jacks of matching general sizes respectively. Transformer T can be a 3W14V or higher power transformer. C1 uses a 1000uF/25V electrolytic capacitor, C2, C3, C4 use 470uF/25V electrolytic capacitors, and C5 uses a 47μF/25V electrolytic capacitor.

1. Installation of components

The capacitors, resistors, diodes, light-emitting diodes, transistors and three-terminal voltage regulator block LM7812 can be welded using a universal printed board according to the previous figure.

2. Welding of the timing start control signal lead-out jack J1

Step 1: Taking the Sendi brand YBC-48L. (14Ah) charger as an example, remove the 5 fixing screws and disassemble the charger casing.

Step 2: Take out the circuit board and find the two-color diode LED1 in the position shown in Figure 6. Note that LED1 is a three-pin combination of red and green diodes sharing a cathode. The top pin is the anode of the green diode, connected to the positive pole of the green drive power supply. The middle pin is the common cathode, grounded (i.e. connected to the negative pole of the drive power supply). The bottom pin is the anode of the red diode. Connect to the positive pole of the red drive power supply.

Step 3: Connect the center electrode contact pin of jack J1 to the anode of the red diode and the outer electrode contact pin to the cathode of the red diode. Note that it is best to solder jack J1 to the two solder points corresponding to the red diode on the copper surface of the circuit board, and pass the two leads through the appropriate position. Finally, install the charger shell.

3. Welding of the three leads of the quartz alarm clock

Step 1: Remove the front cover of the quartz alarm clock.

Step 2: Push the movement out of the back cover of the quartz alarm clock.

Step 3: Take out the watch movement, use tweezers to open the locks around the back cover of the watch movement and remove the back cover of the watch.

Step 4: After removing the back cover of the movement, find the speaker in the movement, open the speaker and find the positive and negative poles of the speaker.

Step 5: Remove the speaker, and weld A and B lines to the positive and negative welding points of the speaker on the core circuit board respectively, and weld C line to the appropriate position of the power negative pole of the core circuit board. It serves as the negative lead of the core power supply. Note that the positive welding point of the speaker on the core circuit board is directly connected to the positive pole of the core DC power supply. Therefore, A line is used as the positive lead of the core DC power supply. B line is the output lead of the core low-level audio pulse signal.

Finally, pass the A, B, and C wires out through the speaker outlet hole on the back cover of the movement, install the back cover, and weld the three leads to complete the quartz alarm clock.

4. Connection between the plug P1 that introduces the timing start control signal and the self-made circuit board

Referring to the schematic diagram, connect the inner pole of the plug P1 to the self-made circuit board through the resistor R2, and connect the outer pole of the plug P1 to the ground of the self-made circuit board.

5. Connection between the three leads of the quartz alarm clock and the homemade circuit board

Referring to the schematic diagram, connect the A line of the quartz alarm clock to the emitter of Q2 (that is, the homemade circuit board is the positive pole of the power supply of the quartz alarm clock), and connect the B line of the quartz alarm clock to the base of Q2, that is, send a low-level audio pulse signal to the base of Q2.

6. Connection between the electromagnetic release coil of AC power switch K1 and the self-made circuit board

Referring to the schematic diagram, connect the electromagnetic decoupling coil of the AC power switch K1 to both ends of the diode D3 of the homemade circuit board in Figure 3 (regardless of positive or negative).

7. Connection between the secondary of power transformer T and the self-made circuit board

Refer to the schematic diagram and connect the secondary of the power transformer T to the rectifier bridge of the homemade circuit board.

8. Connection between the primary of the power transformer T and the AC power switch K1

Refer to the schematic diagram to connect the primary of the power transformer T to the two contact pins 1 and 2 of the AC output of the AC power switch K1.

9. Connection between timing socket and AC power switch K1

Refer to the schematic diagram to connect the timing socket to pins 1 and 2 of the two contacts of the AC output of the AC power switch K1.

10. Connect the power plug to the AC power switch K1.

Refer to the schematic diagram to connect the timing socket to the pins P1 and P2 of the two contacts of the AC input of the AC power switch K1.

IV. Description

Supplementary explanation: In order to facilitate the demonstration of the actual operation of each step, the connecting wires in the pictures have been shortened accordingly. When making it yourself, you should take the wires according to your actual needs. Here, as long as you follow the principle accurately, you can successfully weld this simple timing socket without debugging. Also, be sure to remove the small speaker in the quartz alarm clock. The simple timing socket that I welded and packaged is connected to the charger.

Instructions for use: Before charging, set the timing value first. Connect the charger control signal output jack J1 and the timing control signal input plug P1, connect the charger to the battery, plug in the AC power plug, and finally press the switch K1 button. The simple timing socket will automatically start timing when the charger enters the floating charging state, and automatically end charging when the timing value is reached.

When the charger cannot be switched to floating charge state due to battery problems (such as excessive water loss), the charger plug P1 and the timing socket jack J1 are disconnected, and the timing socket starts timing when it is powered on. When the timing value is reached, charging ends automatically, that is, the charger is charged according to the set value (only used as an independent timing socket).

The simple timing socket has the following advantages: the set value will not be lost when the power is off, no matter how many times the power is off during the charging process. After the call comes in, the simple timing socket only counts the accumulated time of floating charge, because the quartz alarm clock will be powered only when floating charge is on, and the simple timing socket ignores the charging stages before the floating charge stage and only counts the accumulated time of floating charge, thereby achieving the purpose of accurate charging and maintenance of lead-acid batteries.