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Post by SPEKTRE (CR13) on Mar 2, 2012 20:50:52 GMT -5
What does a mosfet do?
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Post by MotorMouth93 on Mar 2, 2012 21:20:54 GMT -5
A MOSFET (or metal oxide semiconductor field effect transistor) is a device that acts as a solid state switch and has next to no internal resistance. When a small current is applied to the "gate" the drain (connected to the motor) is shorted with the source (connected to the battery). Because only a very very tiny current, practically zero when compared to the current flowing through the motor, is required to activate the switch, only a very tiny current has to run through the trigger contacts.
Using the regular wiring system of a gun, the trigger contacts arc each time the trigger is pulled, over time this leads to the pitting and build up of carbon on the contacts, which can render them useless. A MOSFET reduces the current to next to nothing, so the trigger contacts do not arc and destroy themselves. Also, the MOSFET has much lower resistance than the trigger contacts even when they are brand new.
If you are using an 11.1v LiPo battery, MOSFETs are practically a must as those batteries will torch trigger contacts pretty quickly.
The silicon wire is just much better wire than the stuff that comes in guns. It has a much higher strand count than stock wire, and a heavier gauge, so it can carry more current. In the high speed gun that I rewired, the stock wires would get so hot as to almost burn you, this wire got slightly warm.
The Deans Ultra plugs are to replace the Tamiya plugs included on virtually every AEG ever made. Despite their widespread use, Tamiya plugs suck, they are rated for around 15 amps and wear out quickly. I have yet to see a set of Deans Ultra Plugs wear out and they are rated for 80+ amps, they are all I use.
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Post by 88B88888B88B888 on Mar 2, 2012 21:27:00 GMT -5
Somethings that would be nice is where are you located and how often you go to the field. If anything please post an intro.
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Post by MotorMouth93 on Mar 2, 2012 21:40:07 GMT -5
Oops, I guess I forgot about that. Anyway I edited my first post.
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Post by Diamondback on Mar 2, 2012 21:45:08 GMT -5
I might want to try this on the 3rd will you have a demo so we can see how it works?
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Post by MotorMouth93 on Mar 2, 2012 21:50:50 GMT -5
Sure, I'll have my SCAR with me, which has one installed. I'll also bring just a MOSFET by itself, like in the first picture, if you just want to see what they look like.
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Post by dave OC-6 on Mar 2, 2012 22:18:11 GMT -5
hello M.M. welcome to the forum and come by and see me tomorrow, im the field owner.
we don't have many rules here on this forum unlike some others. im sure you will have a great time up here.
please get with all the other UT people here (there are some) and we can talk about what i can do to possibly help get a UT team going.
on another note, please don't do any gun work or take orders here until i meet you, we have had some issues with "air smiths" screwing up and over charging for gun "work". this goes for everyone wanting to do work here, not just you. i want to protect the players, you and me. show me your work and you should be good to go.
thanks and welcome to the forum.....
let the beatings, i mean postings begin!!!!!!
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Post by caliban on Mar 2, 2012 22:27:29 GMT -5
Hey MM, Glad you made it over, look forward to meeting you tomorrow!
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Post by MotorMouth93 on Mar 3, 2012 1:27:53 GMT -5
@dave, sure thing. I'll talk to you first.
Anyway, I'm not bringing my soldering iron.
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Post by Short Fuze on Mar 4, 2012 11:49:15 GMT -5
Motormouth93, do you also sell/make a mosfet + AB unit? If so how much?
AB = Active Braking
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Post by MotorMouth93 on Mar 4, 2012 19:45:39 GMT -5
I don't sell AB MOSFETs as the design has been known to fail catastrophically.
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Post by MotorMouth93 on Apr 8, 2012 19:22:34 GMT -5
Update: I now use the IRLB3034 transistors, which are far superior to the IRF3205 in amp rating and power dissipation.
Also: I am currently in the process of designing a computer controlled mosfet with AB, which I call the CFCU (for computerized fire control unit, it'll have selectable 2-7 rd burst, cycle completion, precocking, etc as well), but that project has been delayed until mid May as school has been crazy lately. So if you have any particular features that you'd like to see in a computer controller for an AEG let me know, and I'll try to incorporate it if enough people like the idea.
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Post by 88B88888B88B888 on Apr 8, 2012 21:42:27 GMT -5
Motormouth93, very VERY interested in your CFCU. I will need to get with you to see if you can fit one into my ak47. I do have a fuse slot that I can get pictures for you and give you the dimensions to see if it would actually fit. Is there a set price that you plan to sell these on? Would love to have one for the Oklahoma Broken Home game. Let me know.
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Post by Short Fuze on Apr 8, 2012 22:18:49 GMT -5
I don't sell AB MOSFETs as the design has been known to fail catastrophically. So this new design with AB prevent from catastrophic failures? |
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Post by MotorMouth93 on Apr 8, 2012 23:04:28 GMT -5
To be honest, I only don't sell the AB version because I would face criticism from some of the senior members on AirsoftForum, which would hurt my credibility on that forum. The people who invented the airsoft MOSFET, and the AB MOSFET for that matter, on AirsoftMechanics denounced their AB design because they thought it was more dangerous and prone to failure, which can cause shorts or runaway firing.
I use an AB mosfet in my main AEG, and it works beautifully. But theoretically, since you have both the positive and negative wire connected to the unit, if one of them fails you have a short instead of just runaway firing like you would with a standard mosfet when it fails. IMO, if you use a fuse you aren't in danger from AB vs standard, but its not a risk I'm willing to take.
But what it comes down to is that I don't want to be held responsible for the death of someones DMR, or their monster lipo going up in flames.
But to answer your question, computer controlled AB is safe, as it is only activates the "brake" for a few milliseconds after you release the trigger.
About the CFCU:
I doubt it will be possible to fit it in an AK without a full stock, I have to fit a microcontroller, a p-channel fet, an n-channel fet, a voltage regulator, a potentiometer, a buzzer, and an 8 dip switch package on the PCB. It'll probably be around 0.75x2x.5 inches.
As for when it will be ready, all I have at the moment is the materials to make a PCB and a basic idea of how I want the code to work. ETA for the first prototype would be sometime in early June or late May.
If all goes to plan, there will be 8 switches on it to configure it, however this could change, and the prototypes will be lacking some features:
DIP0: AB toggle
DIP1: Precocking toggle
DIP2: ROF Control toggle (adds a delay between cycles on full auto or burst, adjustable delay via potentiometer on PCB)
DIP3: Burst settings (000: normal operation, 001: disable full auto, 010: 2rd, 011: 3rd, 100: 4rd, 101: 5rd, 110: 6rd, 111: 7rd)
DIP4: ^^
DIP5: ^^
DIP6: Lipo Monitoring (00: no monitoring, 01: 7.4v cutoff, 10: 11.1v cutoff, 11: 14.8v cutoff...if on a buzzer will go off when the lipo cells reach a dangerous voltage and firing will be disabled until you hold the trigger for 5 seconds to ignore the warning)
DIP7: ^^
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Post by Short Fuze on Apr 9, 2012 9:34:46 GMT -5
Thanks for the clarification!
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Post by 88B88888B88B888 on Apr 9, 2012 11:55:49 GMT -5
If anythign I can always have it wired to the outside the controll unit, and have it set underneath the scope mount where it will be hidden. What other materials are need, maybe could provide the funds for it to get underway. PM if you are interested.
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Post by MotorMouth93 on Apr 9, 2012 19:57:57 GMT -5
Funding isn't much of a problem, the parts would cost around $20. The issue is time, this would take quite a bit of it, and that isn't something that I have at the moment. Right when I started this project my professors also decided to double my workload it seems.
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Post by 88B88888B88B888 on Apr 9, 2012 21:11:11 GMT -5
You should bribe them by showing how slow you can eat a hotdog....It works on poo.
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Post by Short Fuze on Apr 10, 2012 8:27:24 GMT -5
I can see you joined Rising Power Airsoft as well.
BTW I have acquired a 15C continuous / 24C burst 7.4v lipo battery. I may need the mosfet after all. I can purchase a pack of ten for cheap but prefer to help local people instead. You can sell me the parts and I will assemble and install myself. PM me the price.
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Post by MotorMouth93 on May 9, 2012 19:37:35 GMT -5
Just a quick CFCU update: Today I found a suitable development environment to write the code for the microcontroller I plan to use, my last final is this Saturday night (I have no idea who the sicko was that devised Saturday night calculus exams), so hopefully I'll be able to start prototyping and programming next week.
Also, until further notice, I am no longer making MOSFETs aside from the above project. I moved back home for the summer and may start again before August, and I may not, I really don't know at this point.
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thing1
Full Member
I'm going ape
Posts: 166
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Post by thing1 on Dec 31, 2012 11:07:15 GMT -5
I would love to test some of your new MOSFETS out! Im in the market for one anyways (but currently if broke :/). If you need another similar product to look at (for programming) the Avocado ll on evike (although its out of stock). hope to be able to help you out and purchase one of your MOSFETS soon
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Post by MotorMouth93 on Dec 31, 2012 15:10:48 GMT -5
That project was completely scrapped.
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Post by krazyevilcookie on Jan 2, 2013 22:52:06 GMT -5
what do you mean scrapped did you stop making mosfets?
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Post by MotorMouth93 on Jan 2, 2013 23:20:38 GMT -5
I'm no longer building a computer controlled MOSFET, I still install basic MOSFETs though.
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thing1
Full Member
I'm going ape
Posts: 166
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Post by thing1 on Jan 4, 2013 18:33:37 GMT -5
Where can I get a 11.1v battery that will work with the Dean wiring. It goes in the hand guard so it needs to me small, or one of the ones with 3 really flat ones. CC dosent matter, but needs good MaH
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Post by Short Fuze on Jan 4, 2013 19:00:55 GMT -5
Try hobbytown at South Park Meadows!
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thing1
Full Member
I'm going ape
Posts: 166
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Post by thing1 on Jan 4, 2013 19:02:56 GMT -5
Short fuze, do you live in south Austin to? Bowie area?
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Post by Short Fuze on Jan 4, 2013 19:06:39 GMT -5
Yes. By E William Cannon.
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thing1
Full Member
I'm going ape
Posts: 166
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Post by thing1 on Jan 4, 2013 19:08:44 GMT -5
Tight, I'm right of of slaughter! You play at Texas Paintball?
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Oct 8, 2014 21:32:01 GMT -5
Oct 8, 2014 21:32:01 GMT -5