So I’ve finished the board for CREMA Revision A – Prototype 1. It’s a beaut!
I’ll have it printed and wire it up. I can’t wait.
Unfortunately due to size constraints, all components are surface mount (to the exclusion of the Molex headers etc.) Fair warning: unless you have a reflow oven, soldering this board will not be for the faint of heart. There are no components smaller than a 0603 resistor so if you’re good with that, then this will be a breeze!
The prototype has the following functions / features:
- Dual P.I.D. Boiler Control (PWM based)
- Dual PT100 RTD Temperature Sensors with 24-bit resolution providing 0.05°C temperature accuracy
- Single Pump Control (PWM based: allows for pressure profiling)
- 16×2 Display Module
- Onboard real-time clock with two alarms
- Bluetooth or WiFi (using Electric Imp) connectivity for remote control
Some of the design details include:
- Onboard 5V 2,000mA power supply with resettable fuse and ESD protection
- Faston Quick Connect tabs to be compatible with internal wiring of many espresso machines
- Power indicator LEDs for Boiler A, Boiler B, and Pump solid state relays
- Zero-crossing solid state relay to allow precise control of vibratory pumps
- Line-voltage sensors to determine switch states without requiring any special wiring
- Molex connectors with gold-plated pins to minimize connection problems
Once I work out any underlying bugs, I’ll firm-up the firmware and make a public release of the board.