Well the blaster is finished. All the counting, battery measuring, dart firing detection, mag size detection, single/triple/auto firing all working. Turns off the motors (via relay) when out of ammo to save battery, and all working properly.

And i dont like it

The electronics i've put in all work fine, the problem is the belt dart feeding mechanism, its too imprecise. What i mean is, if i have it in single or triple shot mode, the motors get turned off after a single round, or three rounds. Then get turned back on once I release the trigger ready for the next shot. That all works, but the position of the belt and the nubs that grab a dart are too unpredictable. It can push another dart in before it turns off, or it half pushes a dart that enters the flywheel cage but doesnt shoot, but then when i fire next, i get 2 rounds or similar. I just cant think of a way around it.

In a Rapidstrike or something with a more controllable pusher mechanism it'd work fine, but this hyperfire belt drive mechanism just doesnt lend itself to controllable firing.

Moved the IR sensor, but still a bust. They 2 sensors are just too close and the darts are moving too fast. 

At 5cm apart they register with zero millisecond difference. Would work on a longer barrel but at such a short distance theres just no difference in time to measure

Its a great setup for flinging darts in rapid succession, i'll give Hasbro that. But not for control.

OK so i had some wiring issues with how it was installed, was having nightmares with the screen, and getting the IR/RPM sensors working, so i ripped the whole thing apart and re-assembled it properly. Much neater now and no issues.

On the left side of the shell there is the 1.8" screen, joystick, reset button, mag insertion switch, mag size sensors, buzzer, level converter, and of course the arduino.

On the right side, are relay, voltage sensor, dart IR sensor, RPM IR sensor, and power supply. For now its running off standard alkalines, but have replaced all the wiring so it will be getting a LiPo shortly.

The code is about 85% done. At the moment its tweaking things like checking the mag size sensors are set to select properly, make sure all the magazine insertion stuff is in the right order, and that the screen updates properly when things happen. All the code is there, mostly just the order things happen.

There are 2 IR sensors in the barrel, one at the dart insertion point, one at the exit. By measuring the time it takes to get between them, it should give an approximate dart velocity. However when only measured across 10cm, it may not be wholly accurate, but it looks cool

The RPM sensor is also working properly now. On alkalines with stock motors it gets around 11-12k rpm. However i'm measuring every 250ms and multiplying it out, so again its not 100% accurate, but pretty close.

The gear going in the left side:

And the right side installed. The flywheel enclosure and flywheel got a quick spray of black paint to minimise any IR reflections.

The wiring has been upgraded and it will use a LiPo, but i havent yet replaced the motors.

I actually havent done anything on this in ages, have a new job and have been flat out. But yeah, some rather, umm, interesting ideas.

Got it all assembled today and started debugging. For the most part everything is working fine.

Have 2 issues:

I had set it up to measure the current draw of the whole system, but have discovered that sensor is only good up to about a 3A limit. I'm pretty sure the stock motors will exceed that even on alkalines, certainly when i put in a LiPo. I think i can rework it to be good up to 30A though, but need some components from ebay to do it so thats disabled for the moment.

Secondly, i had set it up to measure the speed of the dart. Had 2 IR sensors, one at the entry to the flywheel cage, other close to the tip of the barrel, with about 11cm between them. But ive found because of the rate of fire, it only works if i fire a single dart. Firing more than one results in the second dart triggering sensor 1, just before, or at the same time as, the first dart exits the barrel. This was messing up the calculations, either getting 0 speed, negative speed, or stupid speeds like 50m/s.

I might be able to get it to work by moving the first sensor to the exit of the flywheel cage, but it will reduce the distance and time between sensors, so may mean the result is less accurate, but will give it a go..

I've modded a Rapidstrike and im working on a Hyperfire, so of the 2 i'd go the Hyperfire for the amount of stuff you want to cram into it. It has a good amount of empty space in the orange section at the front, and if you cut out the insides of the battery box, you'll get a huge chunk of room in the rear too.

Theres not a lot of empty space in a Rapidstrike at all.

Found a h=bridge locally!

Current state:

Well, ive started!

Ripped out the existing wiring from the Stampede, removed a few bits of un-needed plastic, and soldered in new wires for the motor, trigger switch, safety switch, and magazine sensor switch. Just waiting for my 11.1V LiPo to charge so i can do some testing on the motor.

Decided to use the existing motor mechanism for now, wired in a h-bridge so the Arduino can control it. Need to do some testing to make sure i can properly control single/triple/full auto shooting.

If i blow it up, or cant get the timing right, then i'll look at using a stepper or servo instead.

These look interesting for a nano. The size is about the same as a Uno, but the good part is that where each pin is broken out to the headers, they also have a +V and GND for each pin.

Handy when you want to connect multiple extras.

So im trying to decide where to mount the screen. It will be on the side of the magazine slot since thats a nice big flat area, but i cant decide whether to put it on the left or right.

Nor can i decide whether to mount it internally, or externally and make a plastic case for it. 

Or to go whole hog and make it fold out.

Thoughts?

Atm i'm leaning towards internally on the left.

Yeah the battery i'm using is rated to 20C continuous, which is why i chose it. I used to competitively race RC cars so know all about batteries, but i didnt know the specs of the motor. The h-bridge i'm using is rated to 4A, and seems to be holding up fine atm.

Will have a look and see if i can find a higher rated one.

Detachable and swappable between sides? Hmmm

Board built, and installed in the battery tray with an 11.1V LiPo.

New wiring in to the relevant switches, screen, and other bits and pieces.

Need to trim the wiring to length and put the proper connectors on instead of the temporary ones i used while testing.

Right, so i got another nano wired in, tested and the screen wouldnt work. Swapped wires around and all sorts, just refused. Tested the screen on a MEGA, worked fine. Can only conclude one of the pins it uses on the nano wasnt working. So scratch that nano.

Grabbed the next one out of my parts box, decide i'll test the screen on it before hooking it up. Plugged it in to usb to load the sketch, wouldnt even power on. Dead as a door nail.

Grabbed ANOTHER nano from the box, plug it to test, and hurrah! powered on! Hooked up the screen, and works! yay! So thats 3 nanos down (those 2 plus the one i blew up). 

Hooked it all up, and all the switches, sensors, screen, and all that work! yay! Next step, hook up the motor and driver. As soon as i turned it on it went to full power. Did some testing and its looked like the FET had failed closed, so just sent the whole battery voltage straight to the motor. Went and got a replacement (luckily only $7 locally), tested it and seemed ok. Wired it in, and slowly started to power it up, and all of a sudden, it went straight to full power as well! Checked the FET and it was red hot! Tested and lo and behold, failed closed again. Its rated to 5A 24V, and i'm only using a 1500mAh 11.1V battery yet it cooked.

I'm going to order a couple of decent H bridges to use instead, so until they arrive the actual motor drive is on hold.

The wiring and software are there for it though, so until they get here, i'll concentrate on getting all the rest of it put together, functional, and tweaking the software to how i want it. Then just have to add the bridge when it arrives.

On the left is the regulated power supply for the arduino etc. Takes the 11.1V from the battery and provides a nice 5V for everything.

The blue board at the top is an i2c voltmeter and ammeter.

The black board at the bottom is a buzzer, for indicating when out of ammo etc.

The nano is obvious.

Then theres a double row of headers on the right that will connect to the various switches, display etc etc in the gun.

Nah i wasnt happy with having the tray going in and out with all the parts in a decent way. So ended up removing the rear of the tray from the main part and just used the bay instead.

Yes that is a switch, just a dpst, but only using one side.

That wire on the spring isnt fully fitted yet, was just laid on top for sizing by length. It will go underneath the spring and be glued down out of the way.

Actually no, the nano can accept 7-12V because of its onboard regulator.

But its not recommended to draw more than 20mA per pin from the arduino, and after i had that IR problem in my Rayven i worked out the actual draw of the bits and pieces that I had connected to the +5V output. The hall effect sensors draw ~10mA each, the IR LED draws about 20mA, the IR transistor about 5mA, 5mA for the buzzer, and up to 10mA for the i2c current/voltage board. Thats 60mA already, then have to add in the 1.8" LCD. I couldn't find the exact specs for the lcd i'm using, but found one similar and it has a 150mA regulator onboard. So max could be looking at 210mA draw. 

Goes way over the per pin rating, and its recommended the whole arduino not exceed 200mA total!

So the regulated power supply runs all the bits and pieces so they don't draw through the arduino, but still get a nice stable 5V.

I was just going to use a 7805 5V regulator, which is $2 locally, plus a couple of $0.50 capacitors for smoothing, and a $2 small bread board to put it on. But when i went to the electronics shop, i saw that little pre made unit for $6. Only $1 more and saved me the hassle of building it, so figured why not?

Good progress on it today! Firing all works now, everything as intended.

Only issue ive discovered is that when the arduino is first turned on, the control pin to the h bridge goes high while it boots. Which means it fires about 5 times when turned on.

Only way i can think of around it so far is to route that signal pin through the safety switch, so wont fire with the safety on. But means i have to remember to turn the safety on every time. 

Edit: occurred to me i might be able to just put a pull down resistor on it, might do the trick.

Edit 2: Yup, pull down resistor does the trick!

Have also decided for practical wiring reasons to put the screen on the right, mounted internally but flush with the side of the mag slot.

Yeah i have a solder sucker and de-soldering braid as well, but of course i have to rip all the wiring off to get to it.

I've ended up just separating the boards out, makes working on it easier. I did accidentally fire it up briefly while testing the battery connection. I think it fed full voltage to the motor, must have been firing at at least 4 rounds/s. Scared the crap out of the dog!

Got sick of soldering/wiring though so put that aside and did some physical work cutting a hole in the shell to mount the screen etc. 

My local electronics store happens to have quite a few arduino bits they get from china.

Its identical to this:

http://www.sainsmart...-1-23v-30v.html

Assuming theres space to fit one. Wouldnt want to try and fit one in a Stryfe or a Rayven.

The little red one is the FET motor driver. Uses the PWM signal from the arduino to drive the motor directly from the battery.

Its lucky i had a bunch of nano's in my parts box. Down to just 4 spares now! Though theres no reason i couldnt use a pro mini, a Uno or even a Mega would fit in the battery compartment of the Stampede.

A H bridge basically is a regulator. Just takes the pwm signal and outputs the proportional voltage to match. The stampede runs on 6x D cells so the motor should run on ~9V anyway, so 11.1V shouldnt be a stretch. I'm guessing the motor controller i was using was designed for an analog signal input instead of a PWM input. Basically fried the FET's input.

Pulse Width Modulation. Basically a digital square wave signal with a variable frequency. Feed that to a motor via a FET and lets you control the speed by controlling the voltage through the FET.

Updated version of the schematic.

I've decided to wire in an extra switch, using the one that was the safety for the jam door.

Figured since the arduino will be controlling the firing, it will be possible for it to shoot 3 rounds, or full auto, with that access open. Could be hazardous to fingers, so going to add it back in as a safety, and add a box to the lcd display saying "Jam Door" or similar.

Since all the parts are in and working, its basically just software now. Should be finished by the end of the weekend!

Dont need to use a full size servo, a little micro servo will work fine as a pusher.

I've got a load of lipo's i can use. 11.1V 2600mAh, 7.4V 4000mAh, and 2x 7.4V 2500mAh. Plenty of room in the battery tray without 6 D cells!

Did a bit of research, the H-Bridge i'm using is based on an L298N driver, which will do 4A and seems to be holding up so far, though the max ive run it at is 60% power.

If (or when) it cooks, i'll replace it with one based on the BTS7960B which can handle 43A. Though I'm guessing thats combined both channels, but its still 21.5A per side.

Checked ebay and they can be bought for $10-12US:

http://www.ebay.com/...fsAAOSwd4tTsNEz

I couldnt see any particular reason for it to be there other than being part of all the various safety mechanisms. Most of which i'll be ripping out or disconnecting.

Made great progress today, had to do some switching around of what is connected to which arduino pin since i had used all the pwm pins for non-pwm functions.

The firing mechanism and detection is all done. Got the jam door open detection and firing prevention working (decided that was necessary after it tried to eat my finger during testing). Got the single/triple/full auto firing working, and stops at 0 ammo. And buzzes to let you know you're out.

Would you believe my biggest problem now is working out where to mount the joystick???

Yeah i was planning to remove the various bits of plastic in the tray and drop it all in there. I could even fit a MEGA in there if i need to, but i have spare UNO's and Leonardos. Once theres a wiring loom taking the various switches, sensors etc back to the tray will just make it easier to work on.

I've had a look at where to put the IR sensor for firing, i'll probably remove that little door flap where the dart inserts, and use the existing opening with just a hole for the LED.

Once this Stampede is done i'll probably re-visit my rapidstrike and add in a stepper or servo to control the pusher.

So far the design looks roughly like this.

Note that this is from memory, probably not the same as whats on my breadboard at the moment so might have errors. I'll update and correct it as I go.

I'm using a MEGA2560 Arduino at the moment simply because it has more flash and ram than the nano's i normally use. That way i dont have to worry about sketch size until its ready to go. Dont yet know what arduino i'll actually use. Whatever I use will be mounted in the battery tray so theres no shortage of space.

The servo may also get swapped for a stepper motor and controller.

This particular design doesnt actually interact with flywheel motors. But, since brushless speed controllers work like a servo with a PWM signal, then yes it would be relatively simple to add in. Would still need a brushless speed controller though.

Nothing major. I'll be using the servo/stepper to push/pull the loading/firing mechanism on the Stampede.

In a Rapidstrike, id use the servo in the pusher instead.

SONOFAM!@#$%&*$#@#$%^&_*&)%^*$@$%!!!

I zapped the arduino accidentally while hooking things up. Fried it

Rebuild time.

Edit: Parts list: http://nerfhaven.com...e-3#entry352455

Edit: Circuit: http://nerfhaven.com...e-3#entry352456

Edit: Arduino code: http://nerfhaven.com...e-3#entry352474

So my first arduino in a nerf was a 7 segment based counter with magazine size detection for a Stryfe and Rapidstrike:

http://nerfhaven.com...nd-rapidstrike/

The mk2 added an OLED screen, and voltage monitoring in a Rayven:

http://nerfhaven.com...hot-counter-v2/

Now comes the mk3 for a Stampede.

This one still has all the things from the others like round counting and magazine size detection etc, but adds a full colour 1.8" LCD screen, battery voltage and current draw display, safety switch, a joystick to select single shot, 3 shot burst, and full auto firing mode selection, and a buzzer to indicate when its out of ammo.

The mk1 and 2 were in flywheel blasters so the motor control wasn't done by the arduino. But the Stampede isn't flywheel, and will have its motor controlled by the arduino which lets me select the firing mode (1/3/auto).

At the moment its breadboarded while i code it, but will probably open up the stampede and start looking at installation this week.

More to come!

Except I'd soldered the Nano onto it.