Kegboard 2
From KegbotWiki
This page outlines potential designs for the next-generation version of the Kegboard controller-board. While it is easy (and fun!) to make one-off boards, the goal here is to come up with a design that is: easy to build from a kit, easy to interface with, and capable of supporting many different tap configuations.
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Contents |
Goals
These features and capabilities are desired for Kegboard 2:
- Four general purpose relays - control four valves, two freezers and two valves, a valve and some lights; whatever
- Four general purpose event counters - connect to flowmeter, bill acceptor, etc
- USB or Ethernet interface; no RS-232 serial
- SMBus/i2c connector - interface with SMBus temperature sensors, Touch Panel, etc
- Firmware remotely upgradable (no special programmer)
- Self test mode - jumper on board to test components, possibly some led indicators
- Few components - better use of component networks etc to minimize solder points
- Few surface mount components - ease kit assembly
Potential designs
All designs shame the same relay circuitry, using N T9AS1D22-5 relays.
PIC16 based
This would be very similar to the first Kegboard. The same microcontroller (PIC16F628A) is used. RS232 option is eliminated, and DLP-USB232M is replaced with on-board FT232R.
Advantages
- Existing design known to work well
- Similarity to existing design means less likely to have errors in PCB
- Good compilers exist (JAL) for target
Disadvantages
- Updating firmware requires special programmer
- FT232R is a surface-mount part (difficult to solder)
Bill of Materials
| Part | Qty | Cost | Comment |
|---|---|---|---|
| PIC16F628A | 1 | $3.35 | Main microcontroller |
| FT232RL | 1 | $3.95 | USB-Serial IC |
| DS18B20 | 1 | $5.04 | Temperature sensor (optional) |
| T9AS1D22-5 | 2 | Power relay | $1.39 |
(incomplete)
PIC18 based
Similar to the PIC18 board but instead uses a Microchip PIC18 part (PIC18F4450 for instance).
Advantages
- DIP pacakge available (easy to solder)
- USB interface integrated into microcontroller (fewer parts)
- Firmware update possible via USB
Disadvantages
- No free compilers generally available
- USB libraries from Microchip anecdotally described as difficult to work with
EZ-USB based
Advantages
- 8051 core with good compiler support (eg SDCC)
- Lots of IO
- Onboard i2c master
Disadvantages
- Surface-mount part (difficult to solder)
- Several external discretes required for typical circuit
AVR
Advantages
- Large, active community
- Good compiler support
- Free firmware-only USB stack exists
Disadvantages
- Author unfamiliar with platform (time investment)
DigiConnect ME
Digi International makes a ~$40 ARM processor with built in ethernet. It also has a TTL serial port and 5 GPIO. The author has succeeded in running linux on this platform. This is somewhat overkill, but it would be possible to use the device as a network-attached kegboard controller.
Advantages
- Author familiarity
- Ethernet!
- Linux!
- 2MB of flash
- Good compiler support (arm gcc)
- Few external components
Disadvantages
- Cost much greater than microcontrollers
