RadioPopper DIYCube

First of all, let me say this: the RadioPopper JrX is so good that I couldn’t wait for RP themselves to activate my Nikon Speedlights. RadioPopper has been an incredible company to deal with and if they had the RPCube – the adapter that enables speedlight control in addition to AlienBees and White Lightning control – I’d be totally on board.

Also, proceed at your own risk. I checked, rechecked, and double rechecked my connections with a multimeter all throughout the build. If you blow something up, it’s not my fault. So let’s proceed.

The key to controlling the power remotely of a typical Nikon or Canon (or other TTL) speedlight, is to take advantage of the TTL mode on the flash itself. As I understand it, while the communication between flash and camera in TTL mode isn’t necessarily as simple as this, the fundamentals involve two signals to trigger the flash (as well as each manufacturer’s proprietary comms). When the shutter is pressed, at the correct time, a trigger signal from the camera turns the light on. Whether calculated on the fly, or beforehand, the intensity of a speedlight is controlled by its duration and thus, when the desired exposure level is over, a quench signal tells the flash to turn off. A series of preflashes and communication as to mode setting and other discussions take place, but these aren’t important to the fundamental task of setting the light level.

The RadioPopper JrX Receiver is capable of this through it’s 1/8″ stereo mini jack on the side. The stereo jack provides three connections: trigger, quench, and signal ground, so in essence, all we need to do is connect these three contacts to the proper pins on our speedlights and voila! remote power control and triggering of our flash.

RadioPopper promises a device called the RPCube which will provide these functions. I can’t wait, so let’s see what we can do ourselves!

A little internet research reveals the pinout of the Nikon hotshoe and identifies the quench pin as the lower right contact (if you are looking down at your camera from the top). Obviously I could have butchered a Nikon TTL cord, but chopping up a 60 dollar cord didn’t seem like an efficient use of materials. I did find the YongNuo AS-10A TTL Multi-Flash Hot Shoe Adapter from DealEtreme.com, a Nikon extension hotshoe (I later found that B&H had a similar part that probably wouldn’t have taken two weeks to arrive from Hong Kong – Update: the similar Nikon part is cheaper, too) so I ordered three (for my three Nikon SB speedlights). While I could have gotten them anywhere, I also ordered two M-M stereo 1/8″ mini extension cables at the same time (each end makes one DIYCube).

The construction of the hotshoe makes it very easy to modify. Four screws hold the case together and give lots of access to the internals. I decided to simply remove one of the three Nikon-proprietary three-pin connectors on the shoe and add a stereo-mini pigtail.

I clipped the wires to one of the connectors and soldered the three conductors from the clipped off end of the stereo mini cable. The stereo plug is configured with the tip as the trigger, the ring as the quench and the shield (base) as the common conductor. The color of your leads may differ, but like I did, I suggest you check and recheck your conductors with a multimeter before you connect your flash.

Finally, with everything connected, it’s time to insulate and close it all up. I was out of tiny shrink tubing, and so I improvised with a little hot-melt glue. A knot in the line provides strain relief (remember to slide the existing plastic mount for the jack you removed onto the cabled BEFORE you start soldering).

How does it all work? Well I did verify that I can change the power of my SB-800 using my DIYCube. I’ll hopefully be using it in the field soon and will give my full review of the system soon.