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Schematic for a rapid fire / turbo button?


Nateo

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Anybody have a decent schematic for a rapid fire button on an Atari joystick? I did some digging on Google, but couldn't quite come up with anything definitive. I'd like to make it variable and have the ability to turn it off, a la the NES Advantage (also tried to look up a schematic for that, to no avail). Thanks all!

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this is a pretty simple idea, tho I don't have an actual schematic to post.

all you need is an oscillator connected to an output switch transistor.

I opened mine up as a kid and it was just a couple/few transistors and a couple of resistors.

It would be very easy to make one out of a 555 timer chip setup as an oscillator and hook an npn transistor

such as 2N2222 to the output as your switch. Google 555 oscillator schematic, and you'll find a bunch, I'm sure

change the main capacitor and add a variable resistor (potentiometer) to make it variable.

you can power it off of the atari joystick port, and have a dpdt on off switch for the power lead.

google 555 variable oscialltor. wish I had my archer engineer's notebook handy, it has a bunch of designs.

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I did'nt realize you were an absolute beginner. Electronics can be a bit rough getting started.

Here's some stuff on ebay that fits the bill. One of them, the lazer, is even variable.

 

 

http://www.ebay.com/itm/PointMaster-Fire-Control-Atari-VCS-2600-by-Discwasher-Auto-Turbo-Fire-/301865464230?hash=item46489571a6:g:gF0AAOSwKtlWhHJC

 

http://www.ebay.com/itm/Atari-2600-LASER-QUICK-FIRE-Adjastable-Auto-Fire-CONTROLLER-NEW-in-BOX/161846098510?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34859%26meid%3Da3267bd6c6c544898ffc40e287c4f011%26pid%3D100005%26rk%3D1%26rkt%3D5%26sd%3D301865464230

 

http://www.ebay.com/itm/PointMaster-Fire-Control-Adapter-for-Atari-2600-or-Sears-Tele-Games/182026735460?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34859%26meid%3Da3267bd6c6c544898ffc40e287c4f011%26pid%3D100005%26rk%3D3%26rkt%3D5%26sd%3D301865464230

 

http://www.ebay.com/itm/Vintage-Atari-2600-Pointmaster-Fire-Control-Constant-Fire-Adapter/201513324784?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D34859%26meid%3Da3267bd6c6c544898ffc40e287c4f011%26pid%3D100005%26rk%3D2%26rkt%3D5%26sd%3D301865464230

 

and here's one of the best books to get you going. Study it, buy a breadboard, and start practicing.

keep practcing till your circuits usually work the first time.

 

http://www.ebay.com/itm/Archer-Engineers-Notebook-Electronic-Circuit-Applications-1980-Edition-/301870263017?hash=item4648deaae9:g:K14AAOSwuAVWvIET

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I've started and stopped with learning electronics a few times, but for some reason, this time around, it has just clicked. Can't explain it, but it all finally makes sense. I think you're right that just tooling around with a breadboard and some simple circuits helps.

Anyways, I found some schematics after googling for "555 autofire". I think I can combine elements of these into exactly what I want!

post-304-0-72748100-1456070579_thumb.gif

post-304-0-49493400-1456070592_thumb.png

post-304-0-61655300-1456070604_thumb.jpg

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Why not just buy a set of these? They give a standard joystick rapid-fire capability without altering the sticks themselves, have a look:
http://www.ebay.com/itm/Lot-of-2-Atari-2600-Rapid-Fire-Joystick-Adapters-Commodore-64-/222020547562?hash=item33b174b3ea:g:icsAAOSwnH1WaFwy

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I've started and stopped with learning electronics a few times, but for some reason, this time around, it has just clicked. Can't explain it, but it all finally makes sense. I think you're right that just tooling around with a breadboard and some simple circuits helps.

Anyways, I found some schematics after googling for "555 autofire". I think I can combine elements of these into exactly what I want!

your first picture is ok, others not so much.

 

Search "555 timer calculator"

You will want something around 12-20 cycles per second (aka Hz). Adjust the 555 timers resistors to get desire result for the games you like.

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Why not just buy a set of these? They give a standard joystick rapid-fire capability without altering the sticks themselves, have a look:http://www.ebay.com/itm/Lot-of-2-Atari-2600-Rapid-Fire-Joystick-Adapters-Commodore-64-/222020547562?hash=item33b174b3ea:g:icsAAOSwnH1WaFwy

Cause it's not as much fun as building it yourself! Besides, I want the frequency to be variable.

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Personally I hate 555 timers, nasty little things can be an arse to get going sometimes. I prefer to program a PIC as they are more accurate and if you get one with an internal oscillator such as the 12F683 the PIC is all you need unless you want variable speed then you would also need a potentiometer.

 

But before you build such a thing do you know if there are enough games on which it would work to be worth the effort?

I know people are always wanting to build them for the Jaguar but in reality I only know of one Jaguar game on which it would actually work and that is because the software looks for a press and release to complete the fire cycle.

I don't know how the majority of 2600 game check the fire input but any system/software that just looks for a single logic level (High or Low) should fire at the maximum rate it can if you just keep the button depressed where the maximum rate is dependant on how often the software checks the input and if the maximum number of sprite the system can handle has been reached.

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Remember the oscillator needs the Atari VCC +5V to operate. Normal joysticks do not have pin 7 (VCC) wired so you will need to use an extension cable with 9 wires present. Generally you want a 555 timer or transistor circuit but 555 timers are easy. You will want a pot connected in series with a fixed resistor for the variable timing.

 

Using the formula provided here:

http://www.ohmslawcalculator.com/555-astable-calculator

 

A 10k pot in series with a 1.2k resistor for R2, and a 22uF cap for C1 will yield a wide usable range from 27.33Hz (just below the theoretical maximum of 30Hz poll rate for NTSC) on the fast end to 2.92Hz on the slow end. R1 in the calculator will be zero ohms (pin 7 of the 555 timer tied to VCC) because we want the duty cycle to be always 50%. It is a good idea to wire an LED into the output circuit as a visual indicator of turbo fire rate. The LED and a current limiting resistor will be series connected between pin 6 of the controller port (fire button) and VCC. This way the LED will illuminate when the fire button is active and indicate turbo speed. A single pole double throw toggle switch will be used to toggle the button between the oscillator output and ground. The timer will run continuously as long as the controller is plugged in, but will only be active along the fire button as long as the turbo switch is activated and the fire button is pressed.

 

For MAME style joystick enclosures with multiple action buttons, a single timer can be used to switch all turbo buttons, with a separate toggle switch to enable turbo for each button. More complex designs offer separate oscillators for adjustable speed on each button, but for the vast majority of games, a separate turbo speed for each button is unnecessary. More commonly, some controllers like Asciiware and Turbografx use two oscillators, with a three poll switch for off-low-high setting (typically 7.5Hz and 15Hz), to select between two speeds on each button. Depending on controller design, they could be digitally tied to the poll rate of the controller or use analog oscillators.

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But before you build such a thing do you know if there are enough games on which it would work to be worth the effort?

I know people are always wanting to build them for the Jaguar but in reality I only know of one Jaguar game on which it would actually work and that is because the software looks for a press and release to complete the fire cycle.

I don't know how the majority of 2600 game check the fire input but any system/software that just looks for a single logic level (High or Low) should fire at the maximum rate it can if you just keep the button depressed where the maximum rate is dependant on how often the software checks the input and if the maximum number of sprite the system can handle has been reached.

 

True, not many 2600 games would benefit from a rapid fire device, but I'm also thinking of use with my Commodore 64, for which there are many shooters where a rapid fire would come in handy. Also, regardless of its usefulness, it just seems like something that would be fun to build as I'm gaining more and more experience with electronics.

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True, not many 2600 games would benefit from a rapid fire device, but I'm also thinking of use with my Commodore 64, for which there are many shooters where a rapid fire would come in handy. Also, regardless of its usefulness, it just seems like something that would be fun to build as I'm gaining more and more experience with electronics.

Many 2600 games only support use of the ball or one of the missile sprites for bullets. So essentially for many games, you can have a maximum of one bullet onscreen at once. When the bullet has collided with a wall or enemy, the game will check to see if fire button is pressed and release another bullet if it is. And some games which do allow you to rapid fire will erase the projectile when you repress the button to generate a new one. A rapid fire in this instance where repeated hitting the fire button resets the bullet would only allow you to shoot immediately in front of your face. Even games which allow up to three bullets onscreen (using both missiles and the ball), the persistence of the sprites will make the turbo fire kind of pointless. You will fire three shots and be unable to shoot again until they hit a target or clear the screen. And generally most of the time, the game reserves the two missiles for enemy projectiles so you're stuck with only one bullet.

 

Lots of NES shooters or run-n-guns only allow three player bullets at a time (although with flicker and slowdown, the hardware often allows far more projectiles onscreen from enemies), and I find myself manually slowing the turbo rate so that they don't all fire as a cluster. Especially if the enemy is invulnerable for a couple frames after taking a hit, shooting a cluster of three bullets at 30Hz fire rate may only do one hit of cumulative damage whereas spreading them out will deal more. Yet with the right turbofire rate, you can just hold the button down while blasting your way through stages playing 8-bit SHMUPs. When you are in your 30s, 40s, and beyond with not so nimble fingers, turbofire can go a long way towards making gameplay more comfortable and preventing repetitive motion injuries.

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Why not just buy a set of these? They give a standard joystick rapid-fire capability without altering the sticks themselves, have a look:

http://www.ebay.com/itm/Lot-of-2-Atari-2600-Rapid-Fire-Joystick-Adapters-Commodore-64-/222020547562?hash=item33b174b3ea:g:icsAAOSwnH1WaFwy

 

Cause it's not as much fun as building it yourself! Besides, I want the frequency to be variable.

Another potential issue is difficulty of not being able to quickly and easily disable the turbo. It appears you would need to unplug the device and direct connect your controller to shut off rapid fire. This is especially tricky in more advanced games that use menu selection or initial entry for high score saving. Tap the button at game over screen for instance and it may instantly record AAA into the initial entry screen.

 

I have personally found that with a good arcade stick with zippy soft touch microswitches, I can rapidly fire as fast as necessary by doing the two finger tap technique on the button. This technique probably won't work well on a CX-40. Your mileage may vary.

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  • 2 years later...

I've unsuccessfully tried a few schematics to add rapid fire to the Vectrex. Last night, I tried the values outline by Kosmic Stardust because 1.) the values work on in the online calculator, and 2.) the values are drastically different from other schematics out there. I figure we're onto something.

 

I breadboarded it unsuccessfully. Here is how I hooked it up.

post-37344-0-18679200-1529752455_thumb.png

 

Can you (Kosmic Stardust) or anyone tell me if I'm missing something obvious here. I suspect I'm screwing something up that might be easy to spot by someone who knows what they're doing.

 

Thanks for any suggestions, Matthew

 

Remember the oscillator needs the Atari VCC +5V to operate. Normal joysticks do not have pin 7 (VCC) wired so you will need to use an extension cable with 9 wires present. Generally you want a 555 timer or transistor circuit but 555 timers are easy. You will want a pot connected in series with a fixed resistor for the variable timing.

 

Using the formula provided here:

http://www.ohmslawcalculator.com/555-astable-calculator

 

A 10k pot in series with a 1.2k resistor for R2, and a 22uF cap for C1 will yield a wide usable range from 27.33Hz (just below the theoretical maximum of 30Hz poll rate for NTSC) on the fast end to 2.92Hz on the slow end. R1 in the calculator will be zero ohms (pin 7 of the 555 timer tied to VCC) because we want the duty cycle to be always 50%. It is a good idea to wire an LED into the output circuit as a visual indicator of turbo fire rate. The LED and a current limiting resistor will be series connected between pin 6 of the controller port (fire button) and VCC. This way the LED will illuminate when the fire button is active and indicate turbo speed. A single pole double throw toggle switch will be used to toggle the button between the oscillator output and ground. The timer will run continuously as long as the controller is plugged in, but will only be active along the fire button as long as the turbo switch is activated and the fire button is pressed.

 

For MAME style joystick enclosures with multiple action buttons, a single timer can be used to switch all turbo buttons, with a separate toggle switch to enable turbo for each button. More complex designs offer separate oscillators for adjustable speed on each button, but for the vast majority of games, a separate turbo speed for each button is unnecessary. More commonly, some controllers like Asciiware and Turbografx use two oscillators, with a three poll switch for off-low-high setting (typically 7.5Hz and 15Hz), to select between two speeds on each button. Depending on controller design, they could be digitally tied to the poll rate of the controller or use analog oscillators.

 

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Did you ever get yours working Nateo?

 

I tried all 4 of the schematics posted to this page, meticulously checking every connection. Fails all around.

 

Finally, I set my full concentration on the "first picture" because Grips said, "your first picture is ok, others not so much."

 

After being 100% certain I'd connected everything correctly with a DMM on every joint, it occurred to me to try a different 555. That fixed it. I spent several hours assuming that part was working.

 

Now I get a very sporadic, semi-slow autofire that speeds up and slows down. Woo! Semi-success!

 

After drinking this coffee and finishing this post, I'm gonna plug Kozmik Stardust's values into the Slovakian schematic (the first one.)

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I've unsuccessfully tried a few schematics to add rapid fire to the Vectrex. Last night, I tried the values outline by Kosmic Stardust because 1.) the values work on in the online calculator, and 2.) the values are drastically different from other schematics out there. I figure we're onto something.

 

I breadboarded it unsuccessfully. Here is how I hooked it up.

attachicon.gifautofire-notworking.png

 

Can you (Kosmic Stardust) or anyone tell me if I'm missing something obvious here. I suspect I'm screwing something up that might be easy to spot by someone who knows what they're doing.

 

Thanks for any suggestions, Matthew

 

 

Hi, yes. The 555 cannot reset with a zero ohm R1 resistor. The astable duty cycle will always be >51% or so. Best case is to use a 1kohm resistor for R1 in place of the jumper, and use a larger pot value for R2 paired with a smaller capacitor value. This will get the duty cycle closer to 50%.

 

There is another schematic for the 555 timer that is supposed to be 50% duty. This version omits R1 and redirects the output into the circuit along with a couple other changes to the design that I cannot recall offhand. You'll never get a perfect 50% duty cycle however as the output impedance of the timer will skew the results ever so slightly.

 

Below 55% or so duty is good. Actually since the turbo schematic is for positive logic, the actual output will be slightly less than 50% duty because the consoles rely on negative logic.

 

Ideally you will want to tune the frequency range from about 4 cycles or so per second up to about 25 or so. Beyond 30 cycles turbo rate is impossible with 60Hz polling because the console has to see a low logic followed by high logic on consecutive frames in order to register multiple presses. So if your turbo circuit goes faster than 30Hz, it will just cause dithering artifacts.

 

EDIT: I looked it up. Here's the modified schematic for 50% duty.

 

tim58a.gif

 

 

The 555 oscillator now produces a 50% duty cycle as the timing capacitor, C1 is now charging and discharging through the same resistor, R2 rather than discharging through the timers discharge pin 7 as before. When the output from the 555 oscillator is HIGH, the capacitor charges up through R2 and when the output is LOW, it discharges through R2. Resistor R1 is used to ensure that the capacitor charges up fully to the same value as the supply voltage.

However, as the capacitor charges and discharges through the same resistor, the above equation for the output frequency of oscillations has to be modified a little to reflect this circuit change. Then the new equation for the 50% Astable 555 Oscillator is given as:

50% Duty Cycle Frequency Equation
tim58b.gif

Note that resistor R1 needs to be sufficiently high enough to ensure it does not interfere with the charging of the capacitor to produce the required 50% duty cycle. Also changing the value of the timing capacitor, C1 changes the oscillation frequency of the astable circuit.

https://www.electronics-tutorials.ws/waveforms/555_oscillator.html

 

If we use your previously mentioned 10kohm pot +1.2kohm as R2, and a 22uF cap as C1, then the above forumula should give you a range in hertz or cycles per second, of 2.92Hz to 27.32Hz, give or take 10% to allow for component tolerances. That is a pretty good range of speeds for a turbo controller. Good luck... :D :thumbsup:

 

Just connect the output of the 555 timer to one side of a single pole double throw toggle switch, and the other side to ground. The middle pin of the toggle switch goes to the common terminal of the FIRE button. NO side of the FIRE button goes to Pin 6. The 555 oscillator will continue to operate all the time whether actively using turbo control or not.

 

I like to connect an LED with inline resistor between Pin 6 and VCC of the controller port. This allows you to see the effects of the turbo schematic in realtime whenever you press the fire button. When turbo mode selector switch is off, the LED will be solid when FIRE is pressed.

 

I hope this helps... :)

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Wow, thank you so much for the detailed response. There's still a lot for me to learn so I appreciate all the resources and thoroughness. I didn't necessarily expect you were still out there or would care to respond to an old thread.

 

I spent most of a Saturday afternoon trying out different values from the different schematics and messed with the calculator to death. I learned breadboard experimentation is key here. I tried this same circuit a couple years ago with a home etched circuit board which required constant desoldering and re-soldering to try new things. Today I went part-by-part and relaunched Minestorm after each swap to see what was happening.

 

Eventually I discovered jumping R1 killed everything (duty cycle under 50%) and that calculator values are merely theoretical when connected to an actual console. :) I never did get the pot to adjust the speed even when the calculator says it should. Also, there's simply a limit to how many bullets the Vectrex can display at once. Aiming for 30Hz isn't even practical. Even 7 shots per second pretty much taps it out until the game catches up.

 

Interestingly, swapping the cap value changed the speed even when turning the pot did not so at the end of my session, I was considering varying the capacitor value with a switch. But with your post in hand, I'll dive back in next weekend. I appreciate your input my friend.

 

....

If we use your previously mentioned 10kohm pot +1.2kohm as R2, and a 22uF cap as C1, then the above formula should give you a range in hertz or cycles per second, of 2.92Hz to 27.32Hz, give or take 10% to allow for component tolerances. That is a pretty good range of speeds for a turbo controller. Good luck... :D :thumbsup:

....

 

post-37344-0-50593400-1529809686.jpg

 

Just now caught up on your cigar box joysticks. Nicely done!

 

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Thanks for your comments regarding the cigar boxes. I was transitioning into doing custom woodbox enclosures (sanded, stained and finished by myself) prior to my finding gainful employment. After working in a hot warehouse all day long, I didn't feel like sitting on a hot patio and working on boxes anymore. Plus factoring in the cost of materials and hours of labor for what they sell for, I probably was making less than minimum wage on the things. But I enjoyed them for a while and may make more in the future... :)

 

On the topic of the 555 equation: Well the theoretical values and actual performance values are not the same. The zero ohm resistor resulting in a 50% duty cycle makes sense from a mathematical perspective but not a practical one. R1 cannot be so small that the transistor connected to pin 7 cannot maintain low logic levels. The transistor output on pin 7 of the 555 timer can only produce a low signal but not a high one. When the signal from this pin is low, R2 passes current until the capacitor is drained to 1/3 of VCC. The 555 timer gets it's name from a pair of comparators inside the chip connected between Ground and VCC using three 5kohm resistors. So pin 6 of the 555 timer is the input to the dual comparators. When the input pin rises above 2/3 of VCC, the output of the 555 timer drops to low logic ~0v and stays there until the input pin falls to 1/3 VCC. When the input pin drops below 1/3VCC, the output of the 555 timer bumps to high logic VCC (~5v) and stays there until the input rises to 2.3 VCC. As long as the input voltage on pin 6 stays between 1/3 and 2/3 of VCC, the output of the 555 timer does not change states.

 

The astable textbook schematic yields a >50% duty cycle because pin 7 of the 555 timer outputs a low logic signal to discharge the capacitor through R2. When the level at pin 6 falls below 1/3 of VCC, the output at pin 7 turns off. At this point, the capacitor is directly charged through both R1 and R2 until the level rises to 2/3 VCC. Because R1 + R2 is greater than R2, the output of the 555 timer in astable configuration will always be greater than 50% duty cycle.

 

The textbook formula dictates a 50% duty cycle for R1 = zero. This is because R2 + R1 = R2 when R1 = zero. However, the low logic signal coming from the internal transistor connected to pin 7 is now shorted to VCC. So pin 7 will be unable to output the low logic signal necessary to discharge the capacitor, because it is dumping a large amount of current into VCC. This excess current could even potentially damage the 555 timer if left in this state for extended periods.

 

The simple mathematics equation does not take into consideration that the current rating of pin 7 of the 555 is finite. And if you factored output impedance into the equation, it would show that excessively small values for R1 would pull too much current from pin 7, causing the low logic voltage level to rise, extending the duty cycle, and eventually causing oscillations to stop entirely once the output pin is no longer capable of pulling the voltage below the 1/3 VCC threshold.

 

So the 50% duty cycle variant of the astable resonator simply removes pin 7 and R1 from the circuit and instead uses the output of the timer to charge and discharge the cap. The output of the 555 timer is not low impedance like the output on pin 7, so timing can be affected by the load presented by the output or the oscillator itself. For turbo button applications, this timing is non-critical.

 

And yes, rapid fire can get messy when too many bullets are onscreen at once. Your turret will tend to fire off a stream of bullets, pause, then fire off another stream. For games like Galaxian or Space Invaders, where you only have one bullet onscreen at once, turbo fire is as good as useless. I think Turbo controllers really shine on later 8-bit and 16-bit generation shooters, where the sprite handling capabilities of the hardware allow for more bullets onscreen than is physically possible by tapping the button manually with one or two fingers. Though there are definitely some Atari games that can benefit from turbo. At the very least it helps prevent RMI (repetitive motion injuries) by letting an oscillator do most of the work. This is especially critical as many fans of classic gaming are now hitting middle age.

 

I hope you get your oscillator working... :)

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Holy chalupa, I had no idea the solution to something as seemingly simple as a rapid fire circuit could get so compkex. I never ended up trying a build of my own due to not having a concrete solution and not enough time to experiment. Cool to see though that there are others than are just as interested in a project such as this!

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...Holy chalupa, I had no idea the solution to something as seemingly simple as a rapid fire circuit could get so complex...

 

And this is the *simple* version believe it or not. A bunch of alternate schematics include extra transistors for activating the fire button, pic micro controllers, all kinds of head spinning things. I was determined to stick with the simplest 555 timer chip. I'll post my super simple drawing once it's perfected.

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  • 3 months later...

 

And this is the *simple* version believe it or not. A bunch of alternate schematics include extra transistors for activating the fire button, pic micro controllers, all kinds of head spinning things. I was determined to stick with the simplest 555 timer chip. I'll post my super simple drawing once it's perfected.

Maybe this will help:

 

http://www.playvectrex.com/vectech/autofire.txt

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Would this be FOR Atari games? I like turbo and all that, but 2600 is a pretty simple beast and most, but not all games fall into two categories. The first being, you can fire as fast as you want, but the older shots will be deleted, and the second being, you can shoot, but nothing will happen until the previous shots hit something or leave the screen.I

 

It's just limitations of using balls to be bullets, which typically you can only have two of at a time (if that, depending on if the game has enemies also firing and how that's handled)

 

Still a cool project. If you could do left and right, you could have a heck of a speed run on decathalon (and similar games)

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Would this be FOR Atari games? I like turbo and all that, but 2600 is a pretty simple beast and most, but not all games fall into two categories. The first being, you can fire as fast as you want, but the older shots will be deleted, and the second being, you can shoot, but nothing will happen until the previous shots hit something or leave the screen.I

 

It's just limitations of using balls to be bullets, which typically you can only have two of at a time (if that, depending on if the game has enemies also firing and how that's handled)

 

Still a cool project. If you could do left and right, you could have a heck of a speed run on decathalon (and similar games)

I used a turbo fire in Star Castle Arcade and Space Rocks and it worked to great effect. Blew through the rings in Star Castle no time. Ditto for Scramble. But those are DCP+ games which can handle up to 4 onscreen bullets simultaneously. Most "classic" Atari VCS games don't have engines that can handle more than one projectile.

 

555 timers are your friends btw. Lots of public domain schematics for turbo circuits available. Use a pot with series resistor for R2 to control the fire rate. You want to dial the frequency range between 4Hz to 25Hz to be usable. There is also a special way to wire a 555 timer up for 50% duty cycle. Basically it removes R1 from the schematic and has the output driving the R2 and C1. I'll try to pull it up later. At work on 3pm break atm.

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