This switch with an indicator light is very popular and inexpensive. There are 6 (six) circuits are discussed on this article, with videos for each circuit. These circuits are easy enough to do in your spare time, on Sundays or holidays. With application example to control a water pump that is outside the house, to make it easy to know if the pump is working. This switch is commonly used for: extension cable, power supply, battery charger, StaVol (Stabilizer Voltage) or Automatic Voltage Regulator (AVR), vacuum cleaner, electrical panel, lamp that is far from the switch or garden light, high pressure pump, boat and ship electric, Air Conditioner (A/C), and so on.
The switch discussed is the KCD4 type, with indicator light only lights up at a high voltage of around 90-250 volts AC or DC. The indicator light is a mini neon (NE-2) which can work with direct current and alternating current, if the voltage is suitable. But the switch can work at low voltage. The photo above shows the switch in the On position or connecting. Written on the red button: 1 is the On position, and 0 is the disconnect or Off position.
Current capacity is 15 Amperes at 250 VAC, and 20 Amperes at 125 VAC.
ATTENTION:
The following circuits are connected to the 100-220 VAC electricity network. Always use well-insulated tools. Do not touch the circuit when it is connected to the power grid. Make sure the fuse or MCB (Miniature Circuit Breaker) is disconnected, when connecting the circuit to the electric grid. Always make sure with the Test Pen there is no voltage on the grid, before connecting the circuit to the grid.
If only 1 (one) grid wire is connected directly to the switch. Then the wire should be the voltage wire (live wire, hot wire), not the neutral wire from the electric grid. To ensure that there is no current to the load when the switch is disconnected (Off).
This switch has 4 pins, which are marked 1 and 2, as in the photo above. But usually the schematic is not depicted on the switch body. When viewed from below it will look like the following image:
Number 1 mark is for the two pins near the edge of the switch.
Number 2 mark is for the two pins in the center of the switch.
There is also a number 3, but no pin. There are also switches with pins marked 2b, 2 and 2a; but it has the same working principle.
The schematic of the switch is as follows:
The indicator light is a mini neon or fluorescent lamp (N). On the schematic it looks like the capacitor symbol, but it has a dot. Actually this lamp requires a resistor of about 150 kilo ohms, which is connected in series as a current limiter. But the resistor is not depicted in the schematic for simplicity. It can be seen that the mini fluorescent lamp is always connected to pins number 2.
CIRCUIT 1
This the most common circuit for KCD4 switch.
Pins number 1 are connected to the power grid (IN), depicted in red. Pin number 2 (OUT) is connected to a bulb as load (L), shown in blue.
As the pin image above. In order for the indicator to light up when the switch is connecting (On), both pins 1 must be connected to a current source or electric grid. Although pins number 2 is not connected, the indicator light can be lit if the switch is connecting. Because the indicator light is supplied from pins number 1.
The number 2 pins are connected to the load or device being controlled. In the drawing above the load is described as a lamp (L).
The following YouTube video shows how to attach KCD4 switch, circuit 1st.
CIRCUIT 2
If the space is narrow, or the distance is long, then only 3 (three) wires can be connected to the switch. The following circuit pin numbers are lettered to make it easier to understand, even though the actual switch has no letter written.
The schematic above shows pins 1a and 1b, all are connected to the power grid. While only one of pins number 2 is connected to the load (L), namely pin 2a. The other wire of the load is connected directly to the grid wire that goes to pin number 1b.
The grid wire connected to pin 1a should be the live wire.
Then pins connection will look like the picture above. It is clear that only three wires are connected directly to the switch.
The following YouTube video shows the 2nd circuit of KCD4 switch.
CIRCUIT 3
This switch can also be installed in different ways, as shown in the following schematic, so that different effects are obtained.
Diagram of pin connections are as follows.
If the connection is reversed: both number 2 pins are connected to the grid (input). Then the indicator light will always be on, when the switch is connecting, or when the switch is disconnecting. Because the indicator light is connected directly to pins number 2, without going through switches. In this configuration both number 1 pins are connected to the controlled device (output).
This circuit is suitable if the switch location is always dark. As it is always illuminated, it's easy to find the switch.
The following YouTube video shows the 3rd circuit of this 4 prongs switch.
CIRCUIT 4
This switch can also be assembled so that the indicator lights up when not connected (Off). And when the switch is connected (On), the indicator will turn off. Usually used for room light control. As in the following schematic.
When the switch is not connected (Off), the indicator lights up. Because pin number 2a is directly connected to the grid. And pin 2b is connected to the grid through the load (L). The load can not work or turn on, because the current through it is too small.
If the load is damaged or broken, the indicator will be off. This is one of this circuit functions, broken load can be immediately known. But if the load is shorted (short circuit), the indicator stays on.
If the switch is connected, then pin 1a is connected to 2a. So that the indicator light turns off, because it has no current passed. The goal is to make the switch easy to find when the room is dark, because the indicator lights up when the room lights are off.
The grid wire which is connected to pin 2a should be the hot wire. Pins connections are as follows.
The following YouTube video shows the 4th circuit of this 4 pins switch.
CIRCUIT 5
The fifth circuit has a mini fluorescent lamp added and connected in parallel with the load.
The circuit above shows a mini fluorescent lamp (N) diserie with a resistor (R) usually 150 kilo ohms. The neon and the resistor are connected in parallel with the load (L). Neon serves as an additional indicator or a second indicator.
The following effects will occur:
If the switch is disconnected (Off) and the load is good, then: the switch indicator is on, the second indicator is off.
If the switch is disconnected (Off) and the load is broken, then: the switch indicator is on, the second indicator is on.
If the switch is connected (On) and the load is good, then: the switch indicator is off, the second indicator is on.
If the switch is connected (On) and the load is broken, then: the switch indicator is off, the second indicator is on.
So this circuit can detect if the load is broken or damaged, even though the switch has not been connected. But can't detect if the load is shorted.
The grid wire connected to pin 2a should be the voltage wire. The connection of the pins are as follows:
The following YouTube video shows the fifth circuit of this 4 prongs switch.
EXAMPLE OF APPLICATION
In this example application, the switch is used to control a water pump outside the house. With an indicator light, it is easy to know that the water pump is working.
Because this indicator switch does not have a housing, the switch is attached to another switch housing as in the photo above.
The red indicator light appears brightly lit, when the switch is turned on, when the room light is turned off or darkened. So even from a distance, it can be easily seen that the water pump is working.
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