Ballast emulator to allow running a video projector without the lamp.
This project provides code for Attiny85 to emulate a "3-wire" or "Ushio ballast" to allow a projector (e.g. Canon LV-X7 whivh I used) to turn on without a lamp (or the original ballast). This allows using a custom lamp or use the LCD or whatever for other purposes.
The operation mode is set by pull-up or pull-down resistors on pins PB3 (ID0) and PB4 (ID1).
Following table shows how the modes are selected, 0=pulled down, 1=pulled up.
| Mode | PB3, ID0 | PB4, ID1 |
|---|---|---|
| Dead | 0 | 0 |
| 3-wire | 1 | 0 |
| Osram | 0 | 1 |
| Ushio | 1 | 1 |
Both ID pins have internal pull-ups enabled, so leaving the pins unconnected selectes the Ushio mode by default.
This mode disables all pull-ups and configures pins as inputs and then sits doing nothing. This can be used to probe the signals or use some external tool to debug/hack the signals even with the emulator connected.
The 3-wire ballast has 3 digital pins for communication: power, dim and sync. The pins are connected as follows.
| Pin number | Name | Use | Direction |
|---|---|---|---|
| 5 | PB0 | DIM | input |
| 6 | PB1 | PWR | output |
| 7 | PB2 | Sync | input |
The Sync pin indicates that the projector wants to turn the lamp on. In this mode the emulator responds
by setting the PWR pin high which indicates that the lamp is powered.
The DIM pin is used to indicate that the projector wants to dim the lamp. The emulator does nothing with this pin.
This is similar serial communication protocol to Ushio, but is currently not implemented. Setting this mode does nothing.
The Ushio ballast uses a serial communication operating at 2400 bps, 8 data bits, 1 even parity bit, 1 stop bit. The pinout is according to following list.
| Pin number | Name | Use | Direction |
|---|---|---|---|
| 5 | PB0 | RX | input |
| 6 | PB1 | TX | output |
| 7 | PB2 | Power flag | input |
The Power flag is not used in the emulator.
The serial communication is handled by a very simple software UART implementation. I have no idea what the messages sent by the projector mean, and the replies are sniffed by people having a working projector (my projector was without lamp so I could only sniff projector messages). I only corrected the decoding presented in the thread. Following message-reply pairs are implemented, and they seem to be enough to turn the projector on.
Message from projector Ballast reply
0x51 0x0D 0x51 0x32 0x0D
0x4C 0x46 0x0D 0x41 0x0D
0x50 0x0D 0x50 0x46 0x0D
0x51 0x51 0x32 0x0D
0x4C 0x45 0x0D 0x41 0x0D -- This is probably incorrect reply