Active brake your AEG without MOSFET's

[killbucket]

I'm using the normal MOSFET layout, wiring-wise, but instead using an automotive 40-amp relay. Of course, you'll need room for the 1 x 1 x 1 relay's box. This circuit feeds full battery power to the motor, saving your trigger contacts from the load.
The active braking will make your gun sound very crisp on firing. It will stop dead when you release the trigger.
The trigger switch feeds ground to the relay's coil, that's it. The relay contacts feed one motor lead. The other motor lead is connected to power. When the relay is on, power is fed to motor, and it spins.
When the relay is off, the relay connects the motor to itself, braking it.
All auto relays use the same pinout, so here's a diagram. Our trigger switch is rated 10amps/250vac, so the ammo drive runs directly from it. If you want to use a micro trigger switch, then use a FET to feed the relay coil and the ammo drive servo.

I'm going to put this into my new AK-74, so I will have a practical example up in photos pronto.
If you have any gun you want to stay on the trigger with, this will give it all the juice it wants without frying the trigger switch.

[Village]

Thanks for sharing! This is really helpful.

[biged]

Quick Q&A for all about trigger switches.

Why active braking?

The active braking idea was developed for guns with high-end motors (Systema Magnum, Systema Turbo) with low voltage batteries 8.4v-10.8v to prevent OVERSPIN.
Overspin is when the gun is fired on SEMI the gun will fire once and compress the piston ready for another shot. Sometimes it will fire 2 shots, it usually it will leave the spring compressed in a random state. An active braking trigger switch will prevent this from happening.

Why a mosfet/relay trigger system?

To overcome big springs instead of increasing gear ratios you can run more voltage through the motor so it has the power to compress the spring. How big of a spring? 450-500 fps guns M150 - M170 springs.
Unfortunately running more voltage 10.8v+ and the added stress of the spring causes resistance in the switch assembly causing it to fail. A mosfet trigger switch or killbuckets relay is a solution.

What the hell is a MOSFET trigger?

Metal Oxide Semiconductor Field Effect Transistor or a very small relay.

///ed//

[CharleyNovember]

Some of us that are not all in the know about mosfets would probally be willing to buy a setup we could just plug into our guns.

[Ersatzjack]

Ditto what AllAmericanDan said. The diagram helps who? No part numbers, or radioshack references or anything. I guess if you have a degree in electrical engineering you could make some sense out of it. It's just enough to whet our appetites for something better but not enough to actually allow us to proceed on a project. But I know that more is to follow, right? Or maybe not. One can always keep their hopes up. Biged at least added some background explanation. Now we need part numbers and vendors. While we're at it I had a great idea that I'm gonna pursue for the AGM MP-40. At least I think it's great and I'll do a post when I finally get back home from another road trip. Lot's of questions have been asked about the TOP MP-40 and internals of the AGM, etc. Well why not make the AGM look like the TOP? How hard would it be to strip the paint off the metal (the AGM is all metal where it counts, right?) and then cold blue the AGM. You could do it to the magazines too. I'm gonna try. I like the AGM but the black paint ruins it. Blued it would be much better along with the fake bake treatment. Then maybe it would finally replace the TOP-40 for the recommended weapon on the recommended weapons page. I'll post my results in a few weeks unless someone beats me to the punch.

Come on Killbucket - just a little more explanation - pleeasse.

[biged]

I recommend running a mosfet trigger in your gun ONLY if you plan on using it in a 450+ fps gun.
Stock trigger switches have been around since they were developed in the 80's. They don't fail unless you run alot of voltage through them.

Gandolf on airsoft mechanics sells mosfets, his website is here:
extreme-fire.com/

///ed///

[Village]

Killbucket threw this up after responding to a PM question I had about his horn relay implementation. Kudos to him for drawing the diagram! Maybe he'll add more info later, but really all the answers you'll need are in his first post.

First, head to AutoZone and pick up a horn relay with the five pins shown. Almost all horn relays have that five post configuration, but if the guy at the counter asks for your vehicle make/model, just say you've got a 2000 Ford F-150 - that should point him in the right direction. Some Toyotas have only three terminals so just make sure you get a five terminal 40-amp relay.

Just wire the AEG's trigger switch into the circuit where illustrated. Observe motor polarity as shown and you're done. I had asked Killbucket specifically about using a microswitch for my MG-42 project. He recommended using a MOSFET for the trigger accuator and triggering that circuit with the lower-rated microswitch. Bigred, thanks for the link! I'm going to order a MOSFET soon.

[Ersatzjack]

Thanks for the added info. That should do it. BTW, anytime I can visit an auto parts store I feel a surge of male pride. Especially if I sound like I know what I need.

[killbucket]

I'm putting the system into an AK-74 today. I'll take pics of how/where things go.
I didn't go into a lot of detail, the info would only be useful for engineering types.
I'm working on a "how to tear down, modify, and re-assemble the Chinese M14 clone" thing. I will add this to it, and you will see the post ASAP. This will be more relevant to the guns you WobblyWobblyTwo guys lust for.
I will include an updated diagram, showing how to do a hybrid MOSFET/Relay that can use any switch, no matter how tiny it is.

Gandy makes a tidy product. It is what you need for most guns, due to space considerations. I have reviewed his designs, he's good at what he does. Passion for an idea makes a HUGE difference!

MOSFET's are only preferable to relays if space is at a premium. 'Fet's that are up to the task are very costly. And I don't know if Gandolf warrants holding the trigger down for extended periods...
A relay has a finite life, only so many cycles before failure. But that number is in the tens of thousands. Other items in a ChiPEG would likely die first. Relay sockets are standard and available if you want a plug-in, replaceable relay sys, but it will eat space.

My D-Boys CH-3381 would notoriously fire twice, or even three shots (if only THAT was consistant) for one trigger pull in semi. This happens most with a fully-charged battery. It is clear the wimpy switch contacts are being ignored.
It stops on ONE shot every time now. My AK-47 Chinee's have the same problem, but not for long.

[CharleyNovember]

I found these units and am ordering one of these. Seems simple enough for a monkey like me to solder it inline and he has good feedback on them. Cheap price aswell.
forums.airsoftmechanics.com/index.php?topic=439.0

[killbucket]

Very slick, very tiny. My circuit is doing virtually the same thing, but with absolutely no worry of frying components. The relay contacts have any FET beat by a country mile for power transmission. Theoretically, the braking is much more instant as well. Any electrical engineer will agree that shorting the motor to itself for braking is the most efficient method to stop it, Now. Relays are just TOO BIG for just about all guns. Unless you know where to hide things well.
I gotta hand it to the designer of that bitty system, it's a beaut.
May have to order one to evaluate myself.
But my guns will stay with the relays, They work flawlessly.

Yes, I am aware a relay has a expectedly shorter lifetime than a FET.
A relay is available everywhere, unlike the FET.

[CharleyNovember]

Yeah size of the unit is why I was looking at the tiny one.