Monday, March 28, 2011

Remote Power and Zoom Control and Readouts For LP160


  • To add remote power and zoom level controls to LP160
  • To add remote power and zoom status readouts to LP160
  • To design and implement hardware and software interface to the LP160
Progress & Summary:

The LP160 appears to be controlled with a PIC mcu. This in turn controls things like flash timings, LED control, etc. I have no desire to reverse engineer the software on the PIC, nor try to decode the communication between it and the rest of the flash. Apart from the tedious nature of that, because I reside in the US, I'll probably run afoul of things like DMCA and various reverse engineering laws.

Method #1:

Handling Readouts:

Instead, I'm intending to interface with the LED signal levels. There are 7 zoom level LED(s), 7 power level LED(s), and 1 ready light LED.
My plan is to employ 2 cascaded 8-bit shift register IC(s) to convert parallel-in to serial-out. The serial out would then be read by an MCU(pic, atmel, etc) to determine the current zoom level, power level, and capacitor charge ready status.
I should also be able to take a thermister and hook it up to one DIO pin and one ADC pin to determine what the internal temperature of the flash unit was, to implement thermal shutdown. 
Handling Commands:

The current LP160 toggle buttons allow you to nudge the setting of the unit down the range of settings, then loop back. The logic is controlled by the onboard PIC mcu.
The simplest way of handling this would be to tie in DIO pins from an MCU to trigger the zoom and power buttons respectively. This can then be coupled with the readout handling to "set" the zoom and power levels to where we want them to.

Method #2 (bypass MCU for power control)
Bypassing the onboard MCU of the LP160 and controlling the flash output power manually through our own MCU. Since the flash power is controlled through an IGBT to control how long a power dump from the powerful capacitor is allowed, one could control this duration one's self through their own MCU. This allows for custom power level settings like 1/6th power, 1/10th power, or even 1/256th power. If one wanted, one could add additional IGBT(s) along with some resistors to adjust the color temperature of the output'd light.

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