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Sharp-02 / JLF-Sharp-Analog-Snap-In

The JLF Sharp Analog Snap-In adds analog functionality to the Sanwa JLF lever
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Sharp Analog Snap-In (SASI) Mod

A fully analog addition to the Sanwa JLF that replaces your lever's restrictor gate. Current Version: 1.2.1

Disclaimer

This repo is undergoing construction. User guides, troubleshooting, and technical explanations are to be expected in the coming months. Files to replicate this are not. To implement the SASI in your builds, please visit https://shopsharpdesigns.etsy.com

Features

Overview

The Sharp Analog Snap-In, or SASI (pronounced "sassy"), adds analog functionality to the pre-existing Sanwa JLF lever.

This mod was made primarily to play Smash Bros. on a fightstick. It is a component of an analog fightstick.

By measuring the position of the bottom of the lever, it outputs an analog voltage that can connect to most controller boards (boards that have 3.3V logic). To do this, the mod mounts magnets that move with the lever, and measures their location through a linear hall-effect sensor. This sensor outputs a voltage, which is amplified to match the 0V-3.3V range that most controllers use. This does not use a microcontroller, and cannot be programmed. A lack of programmability is desireable for cases such as tournament use or for simple implementations. By having no programming, the output is a direct relationship to the lever position and cannot "correct" itself automatically. For it's main purpose, this is just a lever that can replace a thumbstick/analog input.

Analog vs. Digital

The SASI mod snaps onto a Sanwa JLF lever. The Sanwa JLF is a very widespread and easily obtainable lever. However, this lever, like most others on the market, has only digital inputs. A digital input has only on or off states, nothing in between. In practice, this means that you can press up, down, left, and right, but you can't lightly move in one direction. This works well for most fighting games, as there is no change in movement speed depending on how far you press in a direction.

An analog system, on the other hand, does not have only discreet on/off states. Rather, you are able to be somewhere in the middle, maybe at 70% the maximum, or 22%, or whatever resolution your device gives you. For gaming, the SASI mod would allow you to gently move into a direction, or move at a specific angle. You would want this light movement functionality in games such as Super Smash Brothers, where analog inputs are needed for different inputs and actions, or Mario Kart, where adjustments might be made with very slight movements.

What this is NOT is an analog-to-digital system like the programmable Magenta lever by Paradise Arcade. The Magenta lever acts by measuring an analog distance and setting a threshold upon which to count as a "button press". This mod, though it does not remove button press functionality, does not output any button press commands.

Assembly and Installation

The mod is implemented by replacing the restrictor gate of the Sanwa JLF with a custom restrictor gate assembly. In this assembly are the base custom restrictor gate replacement, control PCB with the hall-effect sensors, slider arms that follow the lever's position, and the shroud to maintain the motion of the slider arms.

Electronics

Components:

PCB:

The PCB (printed circuit board) mounts and connects all the electronics. It is shaped to be widely compatible with multiple form factors. On the PCB are the hall-effect sensors that measure the lever position, as well as potentiometers that determine the offset and voltage swing of the individual X and Y axes.

Hall-Effect Sensors:

This modification uses DRV5055 Linear Hall Effect Sensors to measure position of the lever.

The purpose of the hall effect sensor is to measure the strength of the magnetic field and output a signal. The "hall effect" described makes use of the property of flowing electrons to have an induced force in the presence of a magnetic field, otherwise known as the Lorentz Force. The hall effect is an extrapolation of this force, wherein a current within a magnetic field (measured in Tesla) will "bend" as a funcion of the Lorentz force and accumulate charges in a conductor or semiconductor.

There are primarily two types of hall effect sensors seen in use today- the Hall Switch, and the Linear Hall Sensor. The SASI mod uses a Linear Hall Effect sensor, which outputs a voltage relative to the strength of the magnetic field. The sensor used is the DRV5053 whose pins when viewed from the front, from left to right, are: Vcc, GND, and Vout. The "A3" designation indicates that the sensor outputs a voltage of +25mV/mT. The "Q" designation denotes that the temperature range of the sensor is from -40 C to 125 C. The "DBZ" designation indicates the SOT-23 package type.

The DRV5055 sensors used are in an SOT-23 package (surface mount), not the TO-92 package (through hole). Previous versions of the SASI used the TO-92 package.

As the magnet moves along the arrows opposite the sensor, the magnetic field either grows or lessens, depending on which pole is approaching the sensor. This means that, as the magnets are moved by the stick, the sensor will output a voltage depending on the position of the magnet. In testing, the sensor outputs a range from ~1.2V to ~2.2V. [^PCBTest]

[^PCBTest]:The PCB assembly can be tested independent of the full assembly with only a magnet. Orient the magnet's north and south poles along the arrow outlined in front of the sensor under testing. The output voltage can be measured and compared to the expected range (typically 0V - 3.3V).

Op-Amp:

The build is tested on and utilizes the TLC2254 Op-Amp (SMD). This is a rail-to-rail operational amplifier and is the recommended Op-Amp to use for this mod.

The op-amp serves the purpose of amplifying the voltage from the hall effect sensor and applying an offset through the trimpots as outlined below. Other op-amps may work, but are not guaranteed to.

The op-amp is capable of applying a "gain" to an input voltage, which can be summarized as a direct multiplication. For example, a gain of 2 multiplies the input voltage by 2, and a gain of 4.3 multiplies the input voltage by 4.3. The SASI uses the op-amp to multiply the sensor voltage (range of ~1V) to match the voltage range expected by most controllers and controller boards (3.3V). This gain is altered by the relationship of resistors between the op-amps voltage output, voltage input, and ground. On the SASI mod, this can be tuned by turning the GAIN potetionmeters.

The op-amp is also capable of applying an "offset" to an input voltage, or an addition/subtraction of voltage level. As the hall-effect sensors will not output voltages starting at 0V, a "negative offset" must be applied to the sensor's voltage such that the final output voltage is reduced with the lowest output voltage of the mod being 0V. This is tuned by the OFFSET/OFF potentiometers.

The circuit below shows the diagram by which these functions can be performed. Each triangle is an amplifier. The TLC2254 Op-Amp contains four amplifier within its IC package.

What the op-amp does not do is read the input voltage and determine an output voltage or signal like a microcontroller would. Op-amps are not "programmable" in the traditional sense that microcontrollers are. Microcontrollers are capable of more complex interpretations of data, and can perform operations that allow for perfect inputs and timing. Because the op-amp works purely off the analog voltages and circuit design, it cannot be exploited in this manner.

The picture above shows the op-amps capability to amplify the blue signal and shift it up such that a 1V - 2V voltage range becomes a 0V - 3.4V voltage range.

Trimmer Potentiometers:

The trimmer potentiometers, or trimpots, are a type of potentiometer that often come with multi-turn capability at varying levels of precision. Potentiometers are used as a variable resistor, or as a way to connect in the "middle" of a resistor. These properties are utilized in the op-amp circuit shown above.

These trimpots are used to alter the gain (YPOTGAIN, XPOTGAIN) and the offset (YPOTOFF, XPOTOFF) of the output voltage, and are labeled as such. The gain potentiometers adjust how much movement is required to register as a certain position. This potentiometer has a value of 47k or 50k. Adjust this potentiometer if the controller cannot register full motions across the X or the Y axis. The offest potentiometers adjust the center point of the output voltage. This potentiometer has a value of 1k. If the joystick center drifts off center or if the controller can register full motion in one direction but not the opposite (example: 100% left to 80% right), adjust this potentiometer for the required axis. Once soldered, trim the legs below flush to the PCB.

Resistor Network:

All resistors used are 0603 SMD resistors (6mil x 3mil Surface Mount Device). Most of the resistors serve the purpose of setting baselines for the offset and gain on the circuit shown above. You will need 22kohm resistors.

Snapback Filtering:

"Snapback" is a mechanical issue of the spring returning the lever past the centerpoint enough for a controller or game to register a return to neutral as an opposite direction input. This can be remedied through installation of a capacitor to ground, or low pass filter, which can reduce the signal of a sharp signal present in snapback.

There are two locations (top and bottom) dedicated to a "snapback filtering" circuit. The 100 ohm resistor is integrated into this circuit. The remaining component is a capacitor whose value is specific to your setup. Most sticks will not need filtering on their SASI.

Connector:

The JST PH connector is a 2.0mm pitch, not the US standard 2.54mm pitch. This connector must be a 90 degree connector and must face out and away from the center of the PCB. From the front of the PCB, with the connector oriented to the right, the connector pins are as follows: [V+ (top), GND, Signal Y, Signal X (bottom)]. Once soldered in, trim the legs of the connector flush to the PCB.

Mechanical Components and 3D Printing

The mechanical housing and components are designed for and around additive manufacturing processes, most specifically to consumer grade FDM 3D printers. Designs for machined components for low friction polyamide and acetate materials are planned for the future.

Components:

Printed Part Material:

All printed parts are recommended to be printed in Nylon. All parts will undergo a sliding/rubbing motion, and any friction will result in less ideal movements of the lever. If resin printing is available, it is a good alternative. The assembly works fine with PLA/ABS as well, but may require more post processing and frequent application of a dry lubricant.

Restrictor Gate Replacement:

The restrictor gate replacement is the base of the SASI. It houses the PCB, mounts onto the JLF, and acts as it's own restrictor gate. The restrictor gate's shape alters the movement of the stick and limits the shape that it can move along. For example, Gamecube Controllers have an octagonal gate, whereas the Pro Controller and Xbox Controllers have a circle gate.

Which you use is simply a matter of preference. Alternate gate shapes will be added soon. There are no notches in the available files [^notches]

[^notches]: Notches are a controller modification seen in the Super Smash Brothers Melee community that allows for more specific angles to be placed in along the gate. For those interested in implementing controller notches, it may be more difficult to let the stick "lock" into a notch, as the shaft is wide and has a long area that it can slide along.

Slider Arms:

The Slider Arms serve the function of holding the magnets that the hall effect sensors read and, at the same time, wrap around the Sanwa JLF lever such that motions in the lever result in motions of the magnets. They feature a slot in the center into which the actuator of the lever fits into.

The lever may slide along the axis the slot opens, but the lever moves the whole part in the axis of the arms.

These sliders may require post processing, as any imperfections and bumps on the surface can lead to friction and binding in the slider guide. This should be done with sandpaper or careful filing to flatten the sides of the slider arms.

In only one side of each arm, insert a magnet and push it until the magnet cannot go any further. When testing, you may find that the magnet direction must be flipped. Keep this in mind before pushing in too tight or if no tools are available to extract the magnet from the arm (i.e. another stronger magnet). TEST THIS BEFORE ASSEMBLY. If printing in Nylon or another warp-prone material, use the Slider Arm with Brim file, which limits the warping on the small arms.

Assembly and Installation

Assembly and installation of the SASI mod is fairly straightforward. Very little modification to the JLF lever is required. Components stack on top of one another and do not require precise placement of any parts.

Tuning and Testing

Once assembled, connect the analog X and analog Y outputs from the stick to the board you are using, alongside the ground and 3.3V connection. The connection method varies from board to board. Check with the board manufacturer for the recommended connection method to analog stick inputs.

It is recommended to test the stick without installing it in a panel, so that changes can be easily made.

This can be tested either through a joystick viewer found online or in software, or through an oscilloscope by measuring the voltage output. The process remains the same.

Only test one axis at a time. Start by moving the stick fully in one direction, then fully in the other. If the stick shows that it is moving in reverse, extract the magnet under testing, reverse its orientation, and test again.

Next, make note of two different parameters. The first to observe is the "center point" of the output. On a joystick tester, it is as simple as checking if the joystick rests at the middle of the axis you are testing. On an oscilloscope, the "middle" is a level of 1.67V (or 2.5V if you reference a 5V supply). If the joystick isn't centered, turn the axis offset potentiometer (right side) such that the signal becomes centered. Turning the axis offset potentiometers clockwise will lower the middle level, while turning counterclockwise raises the middle level.

Then, once again, move the joystick all the way in both directions of the axis you are testing. If the joystick does not reach the maximum, hold the joystick at the maximum and turn the axis gain potentiometer until it reaches it's maximum. Turning clockwise raises the "sensitivity" of the joystick, while turning counterclockwise lowers it. Once this threshold is hit, hold the joystick in the opposite direction and observe if it reaches the opposite maximum. If it does, still read the next paragraph. If it does not, release the joystick and repeat the steps of the previous paragraph.

This paragraph addresses the "outer deadzone", or the range at which the maximum is reached. Some may prefer that the maximum is reached only at the gate, while some may prefer that the maximum is reached before then. Treat this section as a sensitivity section. Start by identifying what your preference is. Then, slowly move the stick, observing both the physical stick position and the software stick position. If you are not at the measured position that you want, turn the gain potentiometer such that the stick moves in the direction of the desired position. During this process, constantly check if the joystick's resting position is truly the center of the axis.

After all this, repeat the tuning process on the second axis.

The final and most important step for testing is

Play a game!!!

Boot up Dolphin and play some Melee, or see how the joystick feels in Rocket League. Whatever you made this stick for, use it! This is the truest test you can find, and will very quickly identify any problems you have with the SASI JLF mod.