LEMO Connector FGG.1K.302 and FHG.2B.304 Guidelines

Connectors are a very important part of any electronic device. They allow power and data to flow from one machine to another. If you choose the wrong connector, your machine might fail. If you choose the right connector, your machine will work well for a long time.

One of the most famous brands for connectors is LEMO. They are known for a specific design called the "Push-Pull" system. This system is very safe. It locks itself when you push it in. It only unlocks when you pull the outer shell back. You cannot pull the cable to unplug it. This prevents accidents.

This article will explain how to choose between two specific models. The first model is FGG.1K.302. The second model is FHG.2B.304. These two parts look different, and they act different. To pick the right one, you must understand what every letter and number means. We will look at the B series and the K series. We will also look at the difference in their size and their pins.

How to Read the Name

The name of a LEMO connector is like a code. Every letter tells you something about the part. If you can read the code, you can know exactly what the part is. Let us break down the two models you need to use.

Model 1: FGG.1K.302

FGG: This represents the style of the plug. FGG is a "Straight Plug." It is the most common type. It has a key to make sure it goes in the right way.

1K: This part tells you the Size and the Series. The number "1" is the size. The letter "K" is the series. The K series is made for outdoor use.

302: This tells you about the inside of the connector. This is called the insert. The "302" code usually means it has 2 low-voltage contacts.

Model 2: FHG.2B.304

FHG: This represents the style of the plug. FHG is an "Elbow Plug." It is bent at a 90-degree angle. It looks like the letter L. This is good when you do not have much space.

2B: This tells you the Size and the Series. The number "2" is the size. Size 2 is bigger than Size 1. The letter "B" is the series. The B series is made for indoor use.

304: This tells you about the inside. The "304" code means it has 4 low-voltage contacts.

Now that we know the basic names, we need to understand the big differences. The biggest difference is the Series (K vs. B) and the Shell Style (Straight vs. Elbow).

The Difference Between B Series and K Series

This is the most important choice you will make. You must decide where you will use the connector. Will it be inside a clean room? Or will it be outside in the rain?

The B Series (Indoor)

The connector FHG.2B.304 is from the B Series. The B Series is the standard version. It is very popular.

1. Ingress Protection (IP50): The B series has a rating of IP50. This is a technical standard.

The "5" means it is protected against dust. Dust cannot easily get inside to stop it from working.

The "0" means it has no protection against water. You cannot use the B series in the rain. You cannot put it underwater. If water touches it, the electricity might short out. It is made for dry places. You should use it in laboratories, medical devices inside hospitals, or audio equipment in a studio.

2. The Keying System: The B series uses a "Keying" system. This means the plug has small bumps on the metal shell. The socket has small slots. The bumps must fit into the slots. This stops the user from rotating the plug incorrectly. It makes sure the pins inside align perfectly.

3. The Look: The B series looks very nice. It is usually sleek and shiny. It is good for expensive equipment where the design matters.

The K Series (Outdoor)

The connector FGG.1K.302 is from the K Series. The K Series is the rugged version. It is stronger than the B series.

1. Ingress Protection (IP68): The K series has a rating of IP68 when it is mated (plugged in).

The "6" means it is dust-tight. No dust can get in at all.

The "8" means it is waterproof. You can put this connector underwater. This is the main reason to choose the K series. If your machine is a robot that works outside, or a camera that films in the rain, you need the K series. It has special rubber seals inside (O-rings) that stop water.

2. Same Keys as B Series: The K series uses the same alignment keys as the B series. This makes it easy to use. But, you cannot plug a K series plug into a B series socket. The outer shell is different.

3. Rugged Design: The K series is slightly bigger and heavier than the B series. It is built to handle rough handling. It is good for industrial machines, military radios, or outdoor sensors.

Summary of Series Differences

B Series: Indoor use. Not waterproof (IP50). Good for dry, clean places.

K Series: Outdoor use. Waterproof (IP68). Good for wet, dirty, or rough places.

Analyzing the Specific Models

Now we will look very closely at the two specific items you asked about. We will compare them feature by feature.

Model A: FGG.1K.302

This is a Straight Plug. It is waterproof. It is Size 1. It has 2 pins.

Why choose this one? You should choose the FGG.1K.302 if your cable comes straight out of the machine. The "Straight" shape is the standard shape. It is easy to hold. It is easy to plug in.

The Size (1K): Size 1 is small. It is not the smallest (Size 0 is smaller), but it is compact. It is good for devices that are portable but not tiny. Because it is the "K" series, the outer shell is a bit thicker to hold the rubber seals.

The Contacts (302): The number 302 means it has 2 contacts. This is used for simple circuits. For example, you might use it for a simple power connection (Positive and Negative). Or you might use it for a simple signal. Because there are only 2 pins, the pins can be thicker. Thicker pins can carry more electrical current. This model can carry about 15 Amps of current. This is a lot of power for a small connector.

Model B: FHG.2B.304

This is an Elbow Plug. It is not waterproof. It is Size 2. It has 4 pins.

Why choose this one? You should choose the FHG style when you have a space problem. Imagine the front panel of your machine. Maybe there is a door that closes in front of it. A straight plug might stick out too far. The door would hit the plug. The FHG plug is bent at 90 degrees. When you plug it in, the cable goes down (or to the side) immediately. It stays close to the machine. It saves space. It also helps organize cables so they do not stick out and get tangled.

The Size (2B): Size 2 is bigger than Size 1. It is a medium size. Because it is bigger, it is easier to handle if you are wearing gloves. It also has more room inside for more pins.

The Contacts (304): The number 304 means it has 4 contacts. This allows you to do more things. You can send power and data at the same time. For example, you could have:

Pin 1: Power (+)

Pin 2: Power (-)

Pin 3: Data Signal

Pin 4: Data Ground However, because there are 4 pins inside the space, the pins must be smaller than the ones in the 302 model. Smaller pins carry less current. This model can carry about 15 Amps (because Size 2 is bigger, it allows larger pins than a Size 1 with 4 pins).

Detailed Step-by-Step Selection Guide

This section will teach you how to choose between these options. When you look at your project, you must ask these questions in this order.

Check the Environment (The most important step)

Where will the machine live?

Situation A: The machine is inside a warm, dry room. It is a medical cart or an audio mixer.

Choice: You should use the B Series. It is lighter and costs less.

Situation B: The machine is on a boat, or outside in the weather, or in a factory with water spray.

Choice: You must use the K Series. If you use the B series here, water will get in and destroy the connection.

Decision: If you need the FGG.1K.302, it implies you need water protection. If you need the FHG.2B.304, it implies you are indoors.

Check the Space and Cable Direction

How much room do you have in front of the socket?

Situation A: You have plenty of space. You want the cable to come straight out toward the user.

Choice: Use the FGG (Straight Plug).

Situation B: You have very little space. The cable needs to turn immediately to keep the setup tidy.

Choice: Use the FHG (Elbow Plug).

Comparison: The FHG plug is more expensive to make because the metal shape is complex. The FGG plug is simpler and usually cheaper. Only buy the FHG if you really need the angle.

Check the Number of Lines

How many wires are in your cable?

Situation A: You have a cable with 2 wires.

Choice: You need a connector with 2 pins. The 302 type is perfect.

Situation B: You have a cable with 4 wires.

Choice: You need a connector with 4 pins. The 304 type is perfect.

You cannot connect a 4-wire cable to a 2-pin connector easily. You would have to leave wires unconnected. This is bad practice. Always match the number of pins to the number of wires you need.

Check the Electrical Needs

How much power does your device need? We measure this in Amps (Current) and Volts (Voltage).

Current: Large pins carry high current. Small pins carry low current.

FGG.1K.302: This has 2 contacts. They are usually 1.3 mm in diameter. They can carry 15 Amps.

FHG.2B.304: This has 4 contacts. They are usually 1.3 mm in diameter (in size 2B). They can carry 15 Amps.

Wait, they are the same? In this specific case, yes. Even though one is Size 1 and one is Size 2, the pin configuration allows similar power. But you must check the Voltage. Size 2 is bigger, so the pins are further apart. This means it can handle higher voltage before the electricity "jumps" between pins.

FGG.1K.302: Test Voltage is around 1200V.

FHG.2B.304: Test Voltage is around 1800V. So, if you are using very high voltage, the bigger Size 2 (FHG.2B.304) is safer.

Check the Cable Diameter

The connector must fit onto the cable. The back of the connector has a "collet." This is a clamp that holds the cable.

Size 1K: Fits cables from about 1.3 mm up to 8.5 mm.

Size 2B: Fits cables from about 1.5 mm up to 9.9 mm.

If you have a very thick cable, you must use the Size 2 (2B). The Size 1 (1K) might be too small to close around the thick cable. You must measure your cable jacket before you buy the connector.

Understanding the Materials and Assembly

When you buy these parts, you are buying high-quality metal components. It is helpful to know what they are made of. This helps you understand why they are good.

Material Composition

Both the FGG and FHG models usually use the same materials.

Shell: The outer shell is made of Brass. Brass is a strong metal. To make it look nice and resist rust, they plate it with Chrome. This is why it looks silver.

Contacts: The pins inside are made of Brass or Bronze. To conduct electricity well, they are plated with Gold. Gold is the best material for connectors because it never rusts. Even after 10 years, the connection will be good.

Insulator: The part that holds the pins is made of PEEK. PEEK is a very strong plastic. It can handle high heat. When you solder the wires, the plastic will not melt easily.

Assembly Differences

Putting these connectors together takes time. You need tools.

Assembling FGG.1K.302:

Slide the collet nut and collet over the cable.

Strip the wire insulation.

Solder the 2 wires to the 2 pins. This is easy because there are only 2 pins. There is plenty of space.

Push the insulator into the shell.

Since it is the K Series, you must be careful with the seals. There is a potting backshell or a gasket. You must ensure the seal is tight so water cannot get in.

Screw the back nut on tight.

Assembling FHG.2B.304:

This is harder. It is an Elbow plug.

You must prepare the cable.

You solder the 4 wires to the 4 pins. You must be careful. If you use too much solder, the pins might touch each other. This causes a short circuit.

You have to guide the wires around the 90-degree bend. This can be tricky. You must make sure the wires do not get pinched or cut by the metal shell.

There are no water seals to worry about (because it is B series), but the mechanical fit of the elbow parts is complex.

Comparison: The Straight plug (FGG) is much faster to assemble. The Elbow plug (FHG) takes more patience. If you are making 1000 cables, the FGG will save you a lot of time.

Practical Examples of Use

To make this clear, let us look at real-world examples. This will show you why you might pick one over the other.

A Broadcast Camera in a Studio

Imagine a television studio. The camera is on a tripod. It is indoors. The temperature is controlled.

Need: The camera operator needs to plug in a headset. The headset has a microphone and headphones (4 wires total).

Selection:

Environment: Indoor (B Series is okay).

Pins: 4 wires need 4 pins (304 is needed).

Shape: The plug is on the side of the camera. If the plug sticks out straight, the operator might hit it with their arm. An elbow plug is better.

Result: You choose FHG.2B.304. It fits the 4 wires. It stays out of the way. It looks professional.

A Sensor on an Agricultural Robot

Imagine a robot that drives through a cornfield. It measures the soil. It is often muddy and wet. It rains sometimes.

Need: The robot needs a power connection to the battery. It is just Positive and Negative (2 wires).

Selection:

Environment: Outdoor and wet. You must use the K Series. (FGG.1K is needed).

Pins: 2 wires need 2 pins (302 is needed).

Shape: The cable runs along the robot arm. A straight plug is fine.

Result: You choose FGG.1K.302. It is waterproof. It handles the power current. It is tough.

Why NOT swap them?

What happens if you use the wrong one?

If you use the FGG.1K.302 on the studio camera: It will work. But it is overkill. You are paying for waterproofing you do not need. Also, it only has 2 pins, so your headset (which needs 4 pins) will not work. You would need a 304 version.

If you use the FHG.2B.304 on the farm robot: The first time it rains, water will go inside the plug. The water will touch the 4 pins. The electricity will short out. The robot will stop working. Also, mud will get into the mechanism and the latch might get stuck.

Cost and Availability Considerations

When you write a guide about choosing products, you must talk about money.

Price Differences:

B Series vs K Series: The K series is usually more expensive. It has more parts (seals, gaskets). It is harder to make. If you do not need waterproofing, buy the B series to save money.

Straight vs Elbow: The Elbow (FHG) is usually more expensive than the Straight (FGG). The metal shell of the FHG is machined in a complex way. The FGG is a simple cylinder. Only buy the Elbow if you need the space saving.

Size 1 vs Size 2: Bigger connectors use more metal. Size 2 is more expensive than Size 1. If you can fit your wires into Size 1, use Size 1.

Availability: The FGG (Straight) models are the most common. Most shops have them in stock. The FHG (Elbow) models are less common. You might have to wait longer to get them.

Maintenance and Longevity

How long do these connectors last? Both the FGG.1K and the FHG.2B are rated for more than 5000 mating cycles. This means you can plug and unplug them 5000 times. This is a very high number. For normal use, this is many years of service.

Maintaining the K Series (FGG.1K.302): Because this is used outdoors, you should check it sometimes. Look at the rubber O-rings. If the rubber looks dry or cracked, the water protection is gone. You might need to replace the O-ring. Keep the cap on when not in use to keep dirt out.

Maintaining the B Series (FHG.2B.304): This is used indoors. It does not need much maintenance. Just make sure no dust builds up inside the holes. If you use it in a dusty workshop, blow it out with air sometimes.

Conclusion

Choosing between FGG.1K.302 and FHG.2B.304 is not just about picking a plug. It is about understanding your whole project.

Here is the final summary of how to decide:

Look at the water: If there is water, you must pick the K Series (FGG.1K). The B Series will fail.

Look at the wires: Count your wires. If you have 4 wires, you need the 304 insert. The 302 insert only works for 2 wires.

Look at the space: If you are tight on space, use the Elbow (FHG). If you have room, use the Straight (FGG) because it is cheaper and easier to assemble.

Look at the cable size: If your cable is very thick, you might need the larger Size 2 (2B). If the cable is thin, Size 1 (1K) is fine.

The FGG.1K.302 is a tough, waterproof soldier. It carries high power on 2 pins and goes anywhere. The FHG.2B.304 is a sleek, indoor professional. It manages more data/power connections with 4 pins and fits into tight spaces with its elbow shape.

By following this guide, you can be sure that you are buying the correct part. Do not just guess. Read the code (FGG or FHG, 1K or 2B, 302 or 304) and match it to what your machine needs. A correct choice now prevents failure later.

About the Author

I'm an engineer at JINXINYANG Technology, specializing in the IC chip field. I'm dedicated to exploring how various chip technologies work together to drive progress in the digital world. With cutting-edge technology, JINXINYANG provides exceptional IC chip solutions, building a powerful and stable core for your devices.