A Guide to DIN Connectors for Solenoid Valves
DIN is a widely-known standard for connectors and enclosures. Let’s break down the most common DIN connectors for solenoid valves and their circuit functions.
Figure 1. DIN Connector. Image used courtesy of Tameson
DIN connector enclosures protect the electrical circuitry from outside influences and are often rated to IP 65 or IP 67. According to DIN EN 175301-803, the DIN connectors can be used with either hydraulic or pneumatic solenoid valves.
There are several different standards in use within the industry; however, the most common include:
- DIN EN 175301-803 Form A (formerly known as DIN 43650 Form A)
- DIN EN 175301-803 Form B (formerly known as DIN 43650 Form B)
- DIN EN 175301-803 Form C (formerly known as DIN 43650 Form C)
DIN EN 175301-803 Connectors
Let’s review the difference between DIN EN 175301-803 Forms A, B, and C.
DIN EN 175301-803 Form A Connectors
The name Form A in this standard of connectors refers to the standard distance between the pins. As seen in figure 2, the distance between pins 1 and 2 is 18 mm, as standard for Form A connectors. However, there is no difference between 2- and 3-pin connectors. The standard defines the distance between pins 1 and 2, while pin three is the earth connection.
Figure 2. DIN EN 175301-803 Connectors Form A. Image used courtesy of Tameson
Form A 2-pin and 3-pin connectors are available in the marketplace with or without circuit function. The connectors without circuit function can be supplied with AC or DC voltage. The connectors with circuit functions are discussed later in this article.
DIN EN 175301-803 Form B Connectors
Form B DIN connectors for solenoid valves are also called micro connectors. Two main differences set them apart from the Form A connectors.
Firstly, they have a smaller space between the pins, and the connectors can also have two different pin spacings: 10 mm and 11 mm. The 11 mm DIN connectors have three flat blade contacts and are the most common. The 10mm DIN connectors have one flat blade and two U-shaped pins pointing outward, as seen in figure 3.
Figure 3. DIN EN 175301-803 Connectors Form B. The 11 mm connector with three flat blades is on the left, and the 10 mm connector with one flat blade and two U-shaped pins is on the right. Image used courtesy of Tameson
DIN EN 175301-803 Form C Connectors
Form C DIN EN 175301-803 connectors are even smaller than the Form B connectors and are often called the sub-micro connector. As with the Form B connectors, these also come in two sizes under the standard. These are the 8 mm and the 9.4 mm, where the 8 mm has two pins plus earth, and the 9.4 mm has three pins plus earth.
Figure 4. DIN EN 175301-803 Connectors Form C. Image used courtesy of Tameson
Now that we have covered Forms A, B, and C, let’s move on to connectors with circuit function.
DIN EN 175301-803 Connectors With Circuit Function
The circuit function in a DIN connector indicates valve power status. It helps protect the power supply and valve from voltage spikes, rectify an AC power supply to DC power, protect it from transient voltage spikes, and more.
Solenoid valves are expensive and essential equipment, often vital to an operation and used in various applications. Therefore, DIN connectors using the correct circuit are a necessary step in protecting your equipment. The following article offers a helpful source on how solenoid valves work.
The following circuit functions are common and can often be combined.
Light-emitting Diodes (LEDs)
LEDs (light-emitting diodes) indicate valve power status. One advantage of LEDs is that they require less installation time and are easier to troubleshoot. This circuit can be used with AC or DC power supplies.
When selecting LED circuits, consider the available power and valve voltage class, and whether the LED's requirements are met under these conditions.
Power supply and valves are protected from voltage spikes by varistor circuits. AC and DC applications can use this circuit function.
Varistor resistance varies nonlinearly with voltage applied across it. When the voltage is nominal, the resistance is high. As the voltage across the varistor increases, the resistance decreases. A significant voltage spike causes the varistor's resistance to lower, which causes the varistor to conduct and clamp the voltage to a safe level. The varistor will work regardless of polarity.
Figure 5. Circuit with a rectifier, LED, and varistor. Image used courtesy of Tameson
The rectifier circuit converts AC power into DC power. As the circuit typically uses a full-wave rectifier, 90% of the AC voltage is converted to DC. In other words, if you input 230 V AC, it will output ~207 V DC.
Compared to AC solenoids, DC solenoids are quieter, have no inrush current, and can be powered by batteries. Conversely, AC solenoids can be powered by line power, have faster response times, and run cooler.
Pole Protection and Freewheeling Diode
Protecting a switching DC power supply from transient voltage spikes is accomplished through a freewheeling diode and pole protection circuit. A magnetic field is generated when a solenoid coil is powered. If the power supply is shut off, a short-term back electromotive force (EMF) voltage can cause arcing across the switch.
This can be prevented by placing a freewheeling diode across the load, also known as a flyback diode. Current is redirected through the diode instead of the switch when the switch is open. The current is dissipated through the coil rather than across the switch. To redirect the current back through the coil and protect the switch, the polarity of the freewheeling diode in relation to the supply is a crucial aspect.
The diode controls current flow in a pole protector to ensure that the supply’s polarity is always correct. Detecting the wrong polarity will prevent the coil from conducting current. Because of the diode’s conductance properties, it is only feasible to use this circuit with DC power and DC-rated coils.
DIN connectors are used across various industries and applications, partly because they are standardized. It is vital to monitor circuit function because a large overcurrent can cause arcing or explosions. Which DIN Form connectors do you use in your control enclosures?