Strobe Quench Controller Power Supply - Part 1

I had gutted a SEA & SEA TTL C converter and was replacing the innards with a home brew Arduino board that would provide a strobe Quench controller. To review: the Quench Controller would allow me to manually control the power output of my strobes (up to 2 sets of 2) from a single control knob on the TTL converter housing.

Packaging the Arduino

The next challenge was physical. I needed to mount an Arduino Pro Mini board in my reclaimed Sea & Sea TTL converter housing. Should be easy. The housing was much larger than the Pro Mini board. The Pro Mini board was smaller than the Sea and Sea board I removed from the housing.

Don't Forget the Camera!

My test rig and YS50 mule strobe were all working fine. It was now time to get serious and start to hook it up to real equipment.

At first I thought I should tackle jamming the Arduino into the Sea & Sea TTL converter housing. But I decided that I needed 100% confidence in my setup before I started to solder wires to the Arduino. Soldering was a final commitment.

So the next step was to include a real camera into the setup. This required more brain power than I anticipated.

Strobe Quench Controller Operational Theory

I now needed to transform my Sea & Sea TTL converter into an open loop manual power controller for my YS110 strobes. This would provide a single point of power level control so that I did not need to individually adjust the built-in power knob on both of my strobes. Supporting the Canon eTTL protocol was shuffled to the back burner for a while.

The physical TTL converter provided the following features:

Pivot! Decoder -> Quench

My prior work had established a reference set of data messages exchanged between my Canon G16 and a 430EX II flash. Now all I had to do was workup an Arduino program to mimic a 430EX II to the G16 and mimic a Nikonos camera to my Sea & Sea YS 110 strobes.

So far I had been focused on the Canon G16 digital side of my problem. I considered the strobe side to be simple. So I had ignored it. I had focused on developing a Sniffer program that would characterize the G16 to 430EX II protocol. Next step was to think about the big picture decoder problem.

Canon eTTL Protocol Investigation

Having established an Arduino based sniffer complete with an IDE I was finally ready to do some actual real investigation of the Canon eTTL protocol - as spoken by my Canon G16 and a 430EX II flash.

My prior work had indicated that there was constant chatter between the camera and flash. Even in an idle state.

Arduino Bit Bashing Canon eTTL Protocol

I needed to be able to sniff the digital data exchange between a Canon G16 camera and a 430EX II flash. Prior work had determined that the Canon digital eTTL protocol interface was VERY close to SPI. Mostly. Except for signal voltage levels. I had already determined that the Arduino SPI interface was not suitable for sniffing.

Arduino eTTL Protocol Sniffer

The easiest way to investigate the Canon eTTL protocol was to eavesdrop on the conversation between the camera and a flash. This approach would allow me to observe a real working system. I needed to learn about the Cannon eTTL protocol supported by my G16. There was some reference material available on the web but they all cautioned about model differences and misunderstood features. So a sniffer was the way to go.

This required a couple of things I did not have:

Arduino Development Setup

Time to learn how to program an Arduino! How hard can it be? In my early years I was involved in real-time process control and embedded controllers. I even created a patent for weighing garbage. So this was familiar ground, just repackaged and modernized for the hobby crowd. Bonus! Makes my life easier.

Canon eTTL Decoder

The path was clear. If I wanted to control my underwater strobes from my G16, I would need to create a magic decoder box. It would translate between Canon eTTL digital protocol and Nikonos analog TTL protocol. Simple in concept: digital goes in, analog comes out.

This is a problem calling for a microcontroller solution! Easy enough, There are several readily available hobby boards to choose from. Seems like a perfect excuse to spend some time and money playing with technical gadgets. 


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