Obviously - this project was mainly reading and picking through the various other projects written by other H-B'ers. So the work of Peppersass, Jacob, Shawndo, Shadowfax and many others.
Read Dan's warning in the sticky section; this modification modifies both the hydraulic and pneumatic circuits, adds a pump and a mains voltage solenoid. It can shock you if you touch the wrong part. Performing adjustments can scald you and wiring incorrectly can ruin the GS/3 "brain" - the $500-600 3d5 card (and thus ruin your day).
Unlike some of my other projects which were fully annotated (and a few here adopted for their own use) - this project is not well documented for a variety of reasons. It is a bit complex, many of the components are eBay (and tough luck finding the same), and there are probably many adjustments the need to be done. Hence, the annotations below are more descriptive than instructive. While I like to help (and offer my help to anyone who tries this) - please note that there is only so much I can do to help. As I stated - it is for experienced modders. Alternatives such as Ace Sureshot are available that can do some of what this project can do and are probably much easier to install.
What is the GS/3 MOD EP "CHIMERA" about?
I have had the GS/3 for 7-8 years. It is a great machine when maintained well. It is in daily use multiple times daily. As the years progress, other machines pop up. Slayer, GS/3 MP w/Strada mod, Mini Strada, Synesso, many levers like the Londinium, improved and beautiful KvdW, etc.
So in an attempt to bring my GS/3 to modern day "state of the espressive art" standards - here is a spec of a mod I installed over the last month or two.
- a. Profiling modes:
i. Manual profiling - rotate potentiometer to increase/decrease pump PWM voltage - a "poor man's paddle" profiling (One could manually profile pressure or flow - I decided on PWM). A manual profile can be saved.
ii. Pressure profiling - follows the saved pressure reference profile.
iii. Flow profiling - aka H-B member's Jacob's mod - follows the flowmeter ticks of the reference profile.
iv. Union profiling - hybrid profile ala "rule of thirds" - PI using flow profiling, rest using pressure profile. (this mode is buggy doesn't work well at all).
v. Stepped flow ("Slayer like") profile - constant RPM, closed FLB for PI, open FLB for rest of shot.
b. A manual profile may be saved and recalled from on board EEPROM. The profile serves as a reference for the different profile modes and consists of 200 measurement points each of PWM, pressure and flowmeter ticks.
c. System parameters can be adjusted using menus and potentiometer and are stored and retrieved from the onboard EEPROM.
d. Optional 3d5 button support using the Maestro Cash register interface (a serial port onboard the 3d5). Enables one to use the GS/3 buttons instead of manipulating the box.
3. Stepped flow profile (Slayer style) using a medium flow (Cv) metering valve for pre-infusion and a bypass controlled by an FLB (flow limit bypass) solenoid. FLB thresholds and/or timing is adjustable from GUI and stored in EEPROM.
4. Color display & touch screen - "poor man's" espresso digits.
- a. Dashboard shows main pull parameters (PWM, motor current, pressure, flow volume in ml and flow rate in ml/min).
b. Graph shows the reference profiles (PWM, pressure and flow) and overlays the current pull graph.
d. Menu system to select modes and presets.
6. 1gr Strada like use of the original rotary vane pump for the steam boiler; so hydraulics are now completely separate from the pneumatic circuit.
7. If 3d5 serial is integrated, the software can automatically detect cleaning cycle (and has a set PWM for cleaning).
8. Calibration mode for the pressure transducer
9. Separate PID loops control for flow tracking and pressure tracking. PID parameters (like the sliding SetPoint) are shown (for debug) on display near the graph.
10. Increased flow resolution by timing the Gicar flowmeter pulses (currently getting 10% accuracy on the flow rate while in flow limiting).
Future plans are to add EBF (and the ability to shut a flow) control.
The main controller is a small box, with a potentiometer, a status 2 color LED and a touchscreen display (an Arduino shield). Currently 11 wires connect via a makeshift umbilical to the GS3. Cables are Teflon to withstand water steam and heat.
The graphs show the PWM voltage (in red), the pressure (in cyan) and the volume (in green).
The extraction below is a pressure profile pull. The profile was originally created in manual profile mode using the potentiometer, and saved to the EEPROM (non volatile storage). The system can then be set to replicate the same profile automatically. The system can follow either the flow (flowmeter ticks) or the pressure. PID controls the pump motor to try to replicated the reference profile. An additional "safety" against runaways (such as puck fracturing") is limiting the pump PWM to a set band around the reference profiles PWM. The white horizontal line shows at what PWM the preinfusion solenoid is activated.
The graphs show very clearly the aging of the coffee. The green line shows the volume. The volume line sets steeper as the coffee ages. Updosing or grinding finer can help offset the age of the coffee. The sensitivity of age on coffee pull dynamics is pretty remarkable: effect of coffee aging is noticeable on a daily basis.
The following screen shows a different profile - a steeped flow profile. It mimics the Slayer style profile, in that PWM is constant and the user sets the time at which the solenoid valve bypasses the preinfusion metering valve.
Parameters can be adjusted using the potentiometer onscreen. They are saved in EEPROM.
The source code is free to download at https://github.com/alitai/GS3-Transformer. I am not a C++ developer so I apologize for the sloppy code... Obviously additional libraries are needed. See the include section on the main sketch (PID, Adafruit GFX and drivers, Pololu VNH5019 etc.).
Warning - it is still work in progress. At least 1 profile mode does not yet work as it should (the Auto-UP mode). So there will be changes uploaded as time permits.
NB - Obviously, given the flowmeter, pressure sensor and volumetric pump, one can build all sorts of pull modes. One can accurately track a -kx pressure decay of a lever, create the preinfusion piston response of an e61 and replicate almost any other sort of machine. In that - I name this mode the Chimera. But Chimeras are usually ominous. In this case ominous because like having many espresso machines to choose from can make life more complicated.
So for those of us that will savor the ability to play around once in a while - but won't be overly concerned with the possibility that one mode is better than another - this concept is a winner. But those prone to tweaking the knobs with the assumption that out of two options one must be better (a natural by product of linguistics in spite of its logical fallacy) this type of modification may contribute more to confusion than be of assistance.