In the previous installments, we discussed the principle of MOSFETs and a simple implementation circuit, so this time we will actually install one in an electric airsoft gun.
The project involves attaching an XCORTECH XET304μF MOSFET to a PTS Masada.
I chose the PTS Masada, a somewhat rare model, as my subject, but basically all electric airsoft guns are the same.
First, let's look at the MOSFETs that will be installed.
*This article aims to provide educational explanations from a mechanical engineering perspective regarding the safe hobby use of airsoft guns.
This does not promote acts of violence, the use of weapons, weapon modification, practical evaluation, or violation of laws and regulations.
Let's take a look at a real MOSFET.
Let's take a look at the XCORTECH XET304μF MOSFET.
XCORTECH XET304μF MOSFET
I think it strikes a good balance between size, affordability, and maximum power output of 30V/200A. Anything smaller would raise concerns about durability, while anything larger would be cumbersome.
This is the overall circuit diagram (I only researched it myself, so there's a high possibility of errors).
My own research suggested that the circuit board consisted of two MOSFETs in parallel, a protective capacitor, multiple resistors, and multiple SBDs. However, a reader informed me that MF on the board might be some kind of transistor and U1 might be some kind of IC.
My specialty is machinery (and control systems), so I believe the information provided by the reader is correct (please correct me if you're right).
Here is the circuit diagram I came up with last time.
Basically, I think that, as with the circuit diagram above, there is basically some kind of protection circuit for the MOSFET (according to advice from readers, it seems highly unlikely that the protection circuit using my favorite J-capacitor is included).
However, the presence of two MOSFETs and other electronic components I'm not familiar with suggests that it's doing something more complex (I hope it's advanced).
The catalog says 30V. It also says the maximum current is 200A, but I think...It will break if the maximum voltage and maximum current flow at the same time.
A reader advised me on the usage range, suggesting that half the voltage, 15V/100A, would be the safest option (I'm extremely grateful for their help).
I received a comment with more detailed advice, which I think will be very helpful for anyone interested (the comment is at the bottom of the page; I believe the person who gave it was a professional in electrical implementation, unlike me).
Personally, as a mechanical designer, I've found that a safety factor of 1.2 to 1.5 is common, but this MOSFET seems to have a safety factor of 2.0. In situations like this where the load is not clearly defined, I agree that using half of that safety factor is the safest option.
The battery I use is a 7.4V LiPo, and when fully charged it reaches about 8.4V, so the voltage seems perfectly fine.
The current will vary depending on the motor load, so it's difficult to say without careful calculation, but it should probably be fine.
Preparing to install the MOSFET
What you will need to actually install it is
Soldering iron
- Soldering iron stand
・ツールクリップ
・ハンダ
• Signal wire (for gate)
• Input/output wiring (for drain and source)
I think this will suffice.
I'll introduce my recommendations for each.
If possible, I recommend using a soldering iron with a temperature control function. Cheaper ones may have an iron temperature that is too low, making it difficult to melt the solder and taking a long time. Conversely, a soldering iron that is too hot will damage the MOSFET.
Also, since the melting point of solder is around 180-300°C, if you leave the soldering iron on the circuit board for too long, the MOSFET will break very quickly. The limit temperature for MOSFETs is around 150°C, so they really do break very quickly and quietly. I've broken one that way myself, so I think you should be careful.
Soldering iron
This is the curling iron I use. It has a temperature control function and I think it's probably the cheapest one available.
Soldering iron stand
Having a stand to place your soldering iron on is not just convenient, but essential.
Soldering iron and stand set
If you don't have a curling iron or a stand, a set is recommended (you'll definitely need both).
Next is the tool clip.
Soldering MOSFETs is a race against time, so the key is to create an environment that makes it easy for you to work. Three clips are enough. Mine has four clips, but I've only ever used three. In fact, the clips can get in the way, so I recommend using only the bare minimum.
・ツールクリップ
Without them, the work would be almost impossible. Too many clips get in the way (two clips might be enough).
It's best to use solder with a low melting point, but any solder will do for aesthetic reasons. Lead-free solder has a higher melting point, so if you're not concerned about the environment, leaded solder is easier to work with.
Next are the signal lines and input/output wiring.
For signal wires (gate wires), anything that conducts electricity will do, so I choose thin and inexpensive ones. I use Aimon's 0.75 sq wiring, but it's a bit thick, so I cut the core wire in half. Also, since the signal wires will be added and put pressure on the gaps in the wiring, I think it's best to use the thinnest ones possible.
・Amon 0.5 sq wiring
I recommend 0.5 sq wiring. It's from Amon, everyone's friend.
The input/output wiring can be left as is.
Since I'm at it, I always switch to 1.25 sq Teflon and silicone wiring.
I use Teflon cords because they are hard and durable, to connect the motor and MOSFETs, and I use soft silicone cords to connect to the battery to make the most of the battery's space.
Initially, I was using Teflon cords for the battery, but they were too stiff, making it quite troublesome to attach the battery.
Incidentally, using silver-plated wiring improves conductivity, but it's not very cost-effective, so I use copper-plated wiring.
1.25 sq FEP Teflon wire
It's hard and durable, but difficult to work with. I haven't used it since 2022.
Eagle Model Silicone Silver Cord Set (60cm each of red, blue, and black) 16G (1.25 sq)
It's expensive, but I like using it. One unit provides enough wiring for two electric airsoft guns.
I'm not particularly dexterous, but I've been able to successfully install MOSFETs with this tool with a high success rate, so I think it should be fine.
MOSFET installation
First, as preparation, completely disassemble the gearbox and attach the signal wires to the switch. Disassemble the switch as well.
It can be done as is, but if you mess up, the switch will melt because it's made of plastic.
Refer to the distance from the switch to the battery for the correct length. The two black wires you're holding are the signal wires. There are no + or - signs, so don't worry about them.
Next, we'll create the wiring for the motor input. If you're using the original wiring, you don't need to create anything if the length is sufficient.
It's easy; just cut the wires and attach 110-type faston terminals. If you're using Teflon wire, make sure to mark the positive and negative terminals. I cover mine with red and black heat shrink tubing.
For the battery connection, simply cut two pieces of silicone cable to the appropriate length.
Now we connect each wire to the MOSFET.
Please read the MOSFET instructions carefully at this point. Incorrect wiring can have disastrous consequences.
If you notice the mistake before powering it on, you can fix it, but if you power it on, the MOSFET will be destroyed in one go.
First, I start with the motor wiring.
Strip the insulation from the motor wiring to expose the core wire and bend it into a V-shape. Hook the V-shape into the hole in the MOSFET (this explanation uses an XCORTEC XET304μ MOSFET).
Now we'll start soldering.
In my case, I set the soldering iron to 350°C and heat it thoroughly before using it. I melt the solder and apply it to the bent part by dropping it onto the joint.
Here's something to be aware of:Never solder continuously without letting any of the wires cool down (rest).It will break from the heat. Even if it's troublesome, take a breath after working on one part. I broke one this way.
Similarly, solder the signal wires and battery wires to each other.
The signal wires can be connected in either direction (you don't need to worry about polarity), so install them in a way that makes it easy to run the wires.
This will result in the following picture.
Before attaching the heat shrink tubing, trim any excess solder or protruding wires with wire cutters to shape the wire.
Other side
Before attaching the heat shrink tubing, trim any excess solder or protruding wires with wire cutters to shape the wire.
My soldering skills are quite poor, so I'm embarrassed to show it, but this proves that even this level is acceptable (it's just a minimum example, and it works properly).
The MOSFET installation is now complete.
After posting the article, I received soldering advice from a reader (I'm incredibly grateful!).
A good soldering tip is to use a high soldering iron temperature and quickly apply the solder. For cables, it's best to pre-solder them and then bend the wires into an L-shape with needle-nose pliers before threading them through the holes in the circuit board.
More details are available in the comments section, so please take a look if you're interested.
While we're at it, let me show you how to install the fuse and connector.
Fuse installation and T-type connector installation
Fuse installation
We will now install the fuse.
You can use tube fuses, blade fuses, or fuse holders, but the method I'm going to introduce is probably the most compact and inexpensive.
First, use a low-profile blade fuse.
Low-profile fuses, 30A, 10-pack
You don't need a set like the one shown below; you can just buy the fuses you need individually (around 30A for electric airsoft guns).
Next is the Faston terminal type 110. While a gold-plated version is available, the difference in conductivity is minimal, so choose whichever you prefer. Even the gold-plated version costs less than 200 yen.
・110 type Faston terminal set
I don't think it's particularly necessary to be particular about it.
All you really need is a pair of wire strippers. You can use needle-nose pliers if you don't have them, but I don't recommend it.
There are cheaper electrical pliers available than the ones I'm introducing, but the cheaper ones tend to have poor movement or less precision, so I think it's better to spend a little more.
Fujiya Multi-purpose Electrician's Pliers
It's reasonably priced, yet easy to use and sturdy. Furthermore, its larger size is actually more practical.
The work starts here.
First, cut the positive (+) wire coming from the MOSFET to a suitable length.
Strip the core wire from the cut wire and crimp a Faston terminal onto it as shown in the picture.
Next, insert the fuse. It's helpful to reverse the direction of the positive (+) wires.
Simply run the wire through the middle and secure it with heat shrink tubing, and you're done.
I think it's quite small.
Installation of T-type connector
Next, we'll attach the T-type connector for connecting to the battery.
The T-type connector I'm using is the one shown below. It hasn't had any issues with other types of female T-type connectors (though they can be a bit stiff).
T-type connector set
I like it because it's inexpensive and comes in a large quantity. I haven't had any problems with it in my usage.
We will now begin work.
First, expose the core wires of both cables and apply pre-soldering. Just a little is enough. Sorry the photo shows the signal wires.
Next, apply pre-solder to the wiring attachment points of the T-type connector. Pay attention to the orientation of the electrodes and the direction in which you apply the solder. Once the pre-solder is applied, place the wire on the connector and apply the soldering iron to create a clean connection.
All that's left is to put on some heat shrink tubing and you're done.
By the way, here's the size of heat shrink tubing I use. If it's too big, the connector and wiring won't be secured, and if it's too small, the tubing won't fit through the connector. 15mm diameter tubing with a 2:1 shrink ratio works fine.
Heat shrink tubing
This size was a perfect fit for the T-type connector.
This is what it looks like. The heat shrink tubing protects the wiring and also provides a non-slip grip when connecting to the battery, which is convenient.
If you crimp the part between the + and - terminals with needle-nose pliers before the tube cools down, it will look like the picture.
・Needle nose pliers
I don't think you need anything expensive, but things that are too cheap and too small are difficult to use.
Summary and future prospects
You don't need to know how it works; just follow the instructions. However, be very careful with the MOSFET's thermal management. It breaks very easily.
When soldering, do it quickly, but solder the wires slowly, one point at a time. If it gets too hot to touch, you're entering a dangerous zone.
Well, even if you break it, you can get it fixed for 1000 yen, and if you're worried, you could ask someone who can do it or a shop to do it for you.
I don't know how much they charge, but I think it would be faster and cheaper to do it myself.
Regarding future plans, I actually intend to build my own FCU using a general-purpose microcontroller (Ardino, Raspberry Pi). That's why I've gone on at length about MOSFETs as part of my own research. I'm also thinking of using MOSFETs to create things like trigger-linked electric magazines and motor brake circuits.
So, please stick around if you're interested in the continuation of this series about customization.
Comment:
Comment list (9)
I'm a nosy old guy who loves the mechanics and electrical circuits of airsoft guns.
While searching for images using terms like "electric gun," "MOSFET," and "switch," I came across an interesting circuit diagram...
The caption for the photo of "XCORTECH XET304μ MOSFET" is...
I have been reading your blog.
With some exceptions, generally speaking, "Q" on a printed circuit board represents a single transistor or FET, and "U" is the initial letter of a sequential number for ICs, etc.
Therefore, the chip components labeled "M・F" in the photo are likely transistors, and "U1" is probably some kind of integrated circuit (IC).
I've never seen capacitors or resistors of that shape before.
(I apologize if this is incorrect, as he has already retired.)
Also, in that circuit diagram, the DC (direct current) is blocked by the capacitor, so it won't work.
Depending on the capacitance of the capacitor, the gate of the FET may only turn ON for a very brief moment.
The statement says, "We corrected the mistakes after readers pointed them out," but it seems there was some miscommunication.
Dear Gana-san
Thank you for your comment (and thank you for reading my blog).
I looked up the electronic devices on the printed circuit board online using their model numbers. However, my main focus is mechanical design (engines), and I only create the control logic (block diagrams) necessary for their operation; I've only seen the implementation of the electronic circuit boards, so I think what Gana-san said is correct.
Regarding the circuit diagram, I had the impression that semiconductor devices were vulnerable to excessive voltage and current, and also to heat, so I thought some kind of protection circuit (snubber, low-pass) would be necessary and added an RC circuit. However, I realized that the R and C were reversed, and that the mounting positions were wrong in the first place.
So I'm currently rethinking the content of the article.
Thank you for your valuable advice.
As an aside, engines generate a lot of heat and vibration, so protecting electronic devices (including sensors) near the engine (physical protection) was extremely difficult. Therefore, I am aware that we must be extremely careful not only about overvoltage and overcurrent, but also about physical protection.
Once again, I'm a nosy old man who loves the mechanics and electrical circuits of airsoft guns.
Thank you for responding to my comment.
To get straight to the point, I believe the MOSFET connections are more correct in the original circuit diagram.
Based on the photos of the "XCORTECH XET304μ MOSFET" (see other websites as well),
★There are no capacitors on the circuit board. Typical of a Chinese product.
I couldn't find a datasheet for the MOS using the listed model number, so the specifications are currently unknown.
30V/200A likely means 100A per chip, but the catalog simply lists the best value.
That's probably all. So, it's safer to use it at 15V/100V or less, which is half the recommended voltage.
An electric airsoft gun should be sufficient. It's cheap too.
Judging solely from the photos, as I don't have the actual product, the POWER (high current) line is:
[V+]–[U1]Power supply[+]–[D2]Cathode——————————-Motor[+]
[D2] Anode – [MOS1][MOS2] Drain – Motor [-]
[V-]–[U1]Power supply[- ]——————–[MOS1][MOS2]Source
That's what we can determine, but it's difficult to determine the wiring pattern on the control side from just a photo.
It appears that one terminal of the transistor is connected to [V-].
Is this for turning off the MOSFET gate?
(The charge accumulated in the input capacitance Ciss is discharged by shorting the gate to [V-](GND).)
[V+] – Trigger (SW+)
Trigger (SW-) – (TRIGGER) [U1] input
[U1] Output (positive) – [R1 (202)] – [MOS1][MOS2] Gate
[U1] Output (negative) – [Q3] Tr base]
[Q3]Tr Collector]–[MOS1][MOS2]Gate
[V-]———————[Q3]Tr Emitter]
I was wondering if a 2kΩ resistor for [R1(202)] might be too large for the gate,
One side appears to be connected to [V-], and the pattern lines of the [MOS1] and [MOS2] gates are
It appears that it passes under [R1(202)].
[V+] – Trigger (SW+)
Trigger (SW-) – (TRIGGER) [U1] input
[U1] Output (positive) – [R1(202)+] ——————– [MOS1][MOS2] Gate
[U1] Output (negative) —————[Q3] Tr base]
[Q3]Tr Collector]–[MOS1][MOS2]Gate
[V-]———————[R1(202)-]–[Q3]Tr Emitter]
Is that so? I can't say anything more without seeing the actual item.
[U1] is probably a gate driver IC in a "SOT-23-6" package (outer shape).
There are no resistors or Zener diodes for MOS gate protection. Typical of Chinese-made products.
★"I think it represents the output capacitance of the MOSFET." That's incorrect. The capacitance is far too large.
I'm sorry, but this circuit diagram is not good.
The circuit diagram before the revision appears to have the correct MOSFET connections.
Connecting a diode and capacitor in parallel with a motor is the correct connection.
This circuit diagram is incorrect.
Adding a switch to a line carrying a large current defeats the purpose of a MOSFET.
It might make sense if the main power supply is turned off.
You should always remove the batteries from battery-powered devices when you're not going to use them for a certain period of time.
Battery terminal deterioration and corrosion generally occur when batteries are left in, regardless of whether the power is off.
(There shouldn't be any electricity flowing.)
Let's separate the power lines (power supply, high current, high voltage) from the control lines (low current, low voltage).
MOSFETs typically don't have a DS protection diode; they do for transistors, though.
The reason is that the MOSFET pattern in the circuit diagram has a parasitic diode.
As you have written, due to its structure,
A parasitic diode (also called a body diode or built-in diode) is generated between the DS (distributed diode) and the DS (distributed diode).
The voltage and current ratings of this diode are roughly the same as those of the MOSFET.
(Sometimes the voltage rating is half that of the original MOSFET, so the datasheet is essential.)
The protection capacitors around the MOSFETs in this circuit diagram are not needed.
This could lead to malfunctions.
MOSFETs (and semiconductor devices in general, not just MOSs) have parasitic capacitance.
Input capacitance Ciss = Gate-source capacitance Cgs + Gate-drain capacitance Cgd
Output capacitance Coss = Drain-source capacitance Cds + Gate-drain capacitance Cgd
Feedback capacitance Crss = Gate-drain capacitance Cgd
This is because high-current types tend to become bulky.
This is a real problem in amplification circuits (amplifiers, etc.) and high-speed switching circuits (power supplies and logic circuits).
In electric gun MOSFET switches, which are almost simple switch circuits,
You don't really need to worry about it.
In particular, increasing the input capacity Ciss will only slow down the operation.
Most DIY and inexpensive MOSFET switches seem to use just three resistors.
A voltage divider resistor [R1] (approximately 3K to 50KΩ) is connected to the gate.
A voltage divider resistor [R2] (approximately 500 to 3kΩ) is connected to the gate.
A protective resistor [R3] (approximately 100-500Ω) should be connected to the gate.
(As a bonus, a switch protection resistor [R4] (approximately 0-100Ω) is optional.)
[V+]—————-([R4+])–[R1+]
Trigger (SW+) – ([R4-])
Trigger (SW-) ————[R1-][R2+][R3]—MOSFET Gate ★Caution
[V-]—————————-[R2-]
★Note: When the trigger is on, ensure that the divided voltage equals the MOSFET's full on voltage.
When the trigger is off, the divided voltage should be set to the MOSFET's complete off voltage.
Set [R1] and [R2].
★For resistors [Rx+] etc., connect the +/- terminal to either one of the terminals, and connect the unsigned terminal in series.
The POWER (high current) line is the same as above. (One MOSFET is sufficient if it is within the acceptable range.)
Now, the problem here is the voltage divider resistor [R2].
When the trigger is on, [V+] is applied.
A low resistance value naturally leads to a higher current, which is not good.
If the resistance is increased, the charge accumulated in the input capacitance Ciss will not reach the MOSFET's complete off-voltage until the MOSFET is fully off.
It takes time.
In most DIY or inexpensive MOSFET switches, there are trade-offs or compromises.
That's what's set up.
The transistor in "XCORTECH XET304μ MOSFET"
(The charge accumulated in the input capacitance Ciss is discharged by shorting the gate to [V-](GND).)
This is why I considered this, but the shape of the chip components of "M・F" is not only that of transistors.
There are various packages such as diodes and small-signal MOSFETs, so it's impossible to specify.
*Additional note
While your explanation about soldering is generally correct, the "MOSFET's operating temperature limit" and the "soldering temperature" are different things. Otherwise, it wouldn't be possible to produce them using reflow soldering (surface mount soldering equipment).
"Soldering MOSFETs is a race against time." Based on my experience, this is absolutely true, but it's best to use a high temperature on the soldering iron and "pour" the solder into the surface rather than just "apply" it.
When "pouring" the circuit board, ensure that the connected components or cables reach the same temperature.
It's difficult because you have to use a curling iron.
Pre-solder the cables and other components beforehand. They will harden, so needle-nose pliers are essential when bending them.
Also, even with flux-cored solder,
Using flux (a thin layer of the liquid type) is more efficient.
*Another unnecessary addition
In your analysis of "SBD (Schottky barrier diode) in electric airsoft guns"
"The SBD will fail if the temperature rises further due to an increase in leakage current (IR) in a vicious cycle."
Is that based on experience?
While it's true that they can break for that reason, in my experience with DC motor circuits,
This often happens when the voltage rating is exceeded. (Diodes, MOSFETs, transistors, ICs, etc.)
This is not only the "back electromotive force of a DC motor," but also the motor's coil.
This is because the voltage generated by self-induction was not considered, and if this is taken into account...
It gets complicated and I don't think too much about the battery voltage of electric guns.
Let's increase the pressure resistance a bit to avoid this problem.
I understand your specialty is mechanical engineering (plus control systems), while my experience with mechanical systems is limited to tinkering with NC machines.
I've forgotten what a ladder diagram looks like, but when I look at the gearbox of an electric airsoft gun...
I can't help but think, "Couldn't they have done something a little better?"
Despite being an older amateur shooter,
I took the liberty of offering some unsolicited advice, drawing on my past experience.
Your analysis is helpful for understanding the fundamentals.
Dear Gana-san
Thank you very much for all the valuable advice.
I don't really understand the Xcortech circuit board analysis, so I decided not to delve any deeper into it. I also reconsidered the circuit diagram.
Regarding the heat associated with SBDs, as an engine designer, I frequently experienced how semiconductor devices, not just SBDs, can fail due to heat and vibration, so I was very sensitive to heat. The engine's fuel injectors were particularly vulnerable (the same applies to other solenoids).
The electrical department and suppliers had already taken measures to address issues such as high voltage due to coil self-induction and resonance, as well as surge voltages from external factors, so I wasn't too concerned about them by the time the parts came into my possession.
Regarding the mechanism of the electric airsoft gun, it seems reasonable considering mass production and cost (although there are certainly some things that bother me). The NC machine tools that Ganasan mentioned are among the most precise and expensive machines available, so it's understandable that the electric gun looks rather unimpressive in comparison (NC machine tools are considered the king of machines).
My future plans include building my own control circuits using microcontrollers (Raspberry Pi, Ardino), so I would appreciate any advice you can offer.
Incidentally, my specialty is mechanical and engine design, and my electrical work is limited to logic design for mechatronic control (setting up equations using Laplace transforms and drawing block diagrams and Bode plots of response curves). Actual board design and circuit design (E-CAD) are unfamiliar territory for me as I worked in the electrical department (my electrical engineering degree is the end of my education, so I can't implement it).
Therefore, you may notice some oddities, but I would appreciate your understanding and patience (the electrical system field is something that I and the readers will learn together).
Excuse me for bothering you again. (I just had a little free time.)
It seems spaces are omitted when you post. It ended up looking like a strange drawing.
Regarding engines, I've worked on gasoline engine systems for automobiles before.
I definitely never want to do that again (laughs).
Vibration and heat are indeed major obstacles for electrical circuits.
I managed to avoid the sensor system, though...
The noise from the alternator and ignition coil is unavoidable...
The power supply was routed through a coil, capacitor, and surge absorber to an isolated DC-DC converter.
For a while after that job, I wondered why the car stereo was still working properly.
I had forgotten that "NC" is often misunderstood by people working in the machinery industry.
This "NC" is not CNC (Computer Numerical Control) for multi-axis machine tools,
Sheet metal shop (equipment)? In the field of sequence control (PLC) from Mitsubishi, Omron, etc.
This is a field known as relay sequencing.
Nowadays, "NC" refers to CNC (Computer Numerical Control) in NC machine tools.
It seems that the old "NC" is now called "PLC".
*Now, back to the main topic.
Raspberry Pi and Ardino, huh? They're not from my generation, but they're very feature-rich.
There's a wealth of information available. I think it's perfect for having fun.
I recall that the Raspberry Pi cost less than 1 yen in its early days.
The current version is highly functional, even capable of running a Windows emulator (though it's unclear if it's usable).
At that point, the cost of the options becomes quite substantial.
To enjoy it not only for controlling the motor of an electric airsoft gun, but also as a board computer
最適だと思います。
In terms of drawbacks,
Since it's a board computer, it's too big to integrate into an electric airsoft gun.
(There are smaller models available in the lower price range.)
It's far too high-performance to be used solely for controlling the motor of an electric airsoft gun; it would be a waste.
Currently, they are in short supply and expensive (you could buy a plug-in brushless motor for that price).
A single-chip microcontroller is primarily used to control the motors in electric airsoft guns.
MICROCHIP's PIC microcontrollers and Atmel's AVR microcontrollers are probably the most common.
I believe ATMEL was acquired by MICROCHIP, but both companies still ship microcontrollers.
There is a wide variety of functions, types, and packages available.
I don't need anything expensive (high-performance), so would something costing around ¥500 each be sufficient?
In terms of drawbacks,
There is less information available about it compared to Raspberry Pi, Ardino, etc.
(Even within the same series of 1-chip microcontrollers, information on the exact same part number is often unavailable.)
Development tools (program writing devices) are required and are relatively expensive [around ¥4,000 to ¥10,000].
If it's a PIC microcontroller from MICROCHIP, will it be depreciated upon retirement?
I have a lot of items that were scheduled to be discarded. Do you want them?
PIC24FJ64GB002-I/SP 28pin PDIP
dsPIC33EP256MC502-I/SP 28pin PDIP
PIC32MX250F128B-I/SP 28pin PDIP
And so on.
There are others, but they come in packages like 64-pin TQFP, which I think makes them difficult to use.
There are about 10 of each, and it's rather strange that they aren't the commonly used [PIC16] and [PIC18]...
What's even more impressive is that it's even more feature-rich than those...
Although it's an older model, I also have spare "pickit3" development tools (program writing devices) available.
Please gather information by searching the web when you have some free time.
If you're interested, please send me an email.
The "plug-in brushless motor" that came up in the middle of the conversation...
We only have the "OPTION NO.1" brushless motor.
(Other manufacturers are too suspicious)
However, if you use this, (a MOSFET switch will still be necessary)
I somehow feel like I lost.
Basically, the Tokyo Marui EG-1000 motor is the only option.
If you're going to buy a Tokyo Marui samarium-cobalt motor
I'll choose this one. (Even though it's expensive.)
*Additional note
Regarding the gearbox of an electric airsoft gun, while there are structural issues, the thing I dislike most is that it's "heavy."
Even if you tolerate the fact that it's made of die-cast metal, looking at the gearbox of the new model, you can see that they've calculated the strength and removed material.
It is not designed in a way that would relieve stress concentration at the corners.
This is a reckless act of increasing the number of points where you might think, "Won't this break if force is applied?"
I doubt that product feedback is being provided.
I can't help but wonder if they're intentionally making the molds easy to copy.
(Well, thanks to that, I don't have any trouble buying parts.)
The difference in quality compared to gas guns is significant (although if it were at that level of quality, the price would be understandable).
I feel the price is too high for that.
(Is this product such a cash cow for the manufacturer that they're unfazed by Chinese copies?)
This has turned into a rant that's not really related to anything "heavy," so I'll stop before it gets worse.
excuse me.
I see, you mean a PLC. My image of one is a machine tool with a huge control panel.
In any case, I think machine tools used by professionals are the king of machines.
I personally plan to use microcontrollers like the Raspberry Pi for the development and consideration of FCUs, and after deciding on the control logic, I intend to create the implementation circuit using logic circuits and other electronic devices on a general-purpose board.
I think that microcontrollers like the Raspberry Pi are simply too large and too feature-rich to be directly installed in an electric airsoft gun.
I've also used the OP1 brushless motor and written a blog post about it. It's expensive, but I thought it was easy to assemble without having to think about anything (does that make me feel like I've lost?).
Finally, regarding the mechanics of the electric airsoft gun, I agree with you that there are some shortcomings in the design of each component. There are many points that raise questions, not only about the box itself, but also about the design of the gears and the basic and important positioning.
However, I think it's acceptable because it's structurally sound, and there are plenty of areas where even a consumer like me can tinker with it (which wouldn't be acceptable for a machine like a car that involves human lives).
If you enjoyed it, I hope you'll continue to enjoy it in the future.
The circuit diagram is almost finished. (Am I sounding condescending?)
I read your blog posts related to "MOSFETs."
Based on my experience, it seems you've had quite a hard time with this. Perhaps that's why the protection for the MOSFET is excessive.
"Upon further consideration, the back electromotive force generated by a DC motor is quite large instantaneously, so it seems safer to add a protection circuit (snubber circuit) to the SBD circuit as well."
Even though some people recognize the correct, or rather, appropriate, answer, they've gone on to discuss MOSFET protection instead.
As I mentioned before, there are parasitic diodes in the MOSFET, so let's remove the SBD in the protection circuit as well.
Snubber circuits are effective for devices with physical contacts, such as switches, relays, and solenoids.
A MOSFET operates as a switch, but it doesn't have physical contacts (it's controlled by the gate voltage).
Think of it as something like a potentiometer that can vary from ultra-high resistance to ultra-low resistance.
Analog amplifier circuits (amplifier circuits), etc., are generated from the gate cutoff voltage (ultra-high resistance, so-called off state).
It utilizes the period during which the gate is operating (saturating) at high voltage (ultra-low resistance, the so-called ON state).
(It's similar with transistors.)
Let's remove the snubber circuit as well.
Conversely, to handle the self-induction and back EMF of a DC motor, you should install an SBD (Snubber Diode) or snubber circuit on the DC motor.
The motor in an electric airsoft gun does not rotate at a constant speed due to on/off operation, so the constants of the snubber circuit cannot be determined.
To save time, let's remove the resistor and just use the capacitor. (It's a bit of a rough solution, though.)
In other words, the motor is connected in parallel with an SBD and a capacitor.
With this, the motor's self-induction and back EMF are contained within the motor circuit.
And once completed, it will have the same circuit as a homemade or inexpensive MOSFET switch sold commercially.
*Additional note
In reality, when semiconductor devices, including MOSFETs, are switched, they momentarily enter a negative potential state, regardless of whether they are powered by a single power supply.
When observing logic circuits and other components with an oscilloscope, you can see that they produce something resembling whiskers.
Based on experience, this cannot be eliminated. (The cause is difficult to identify, such as wiring patterns or bypass capacitors, and even if identified, it is impossible to fix.)
The only option is to make it small enough so that it doesn't malfunction.
That's all from a meddlesome old man who's obsessed with the mechanics and electrical circuits of airsoft guns.
*An unnecessary addition*
Adding this to avoid misunderstandings.
The statement, "It will momentarily become negative," was written in a way that could easily be misunderstood, implying that a positive potential would always become negative.
Rather, it's something that happens in relatively high-speed logic circuits, etc. (Some circuits don't experience this.)
My own experience is quite biased, isn't it? My apologies.