Canon 540EZ DIY Sync Port

After coming away from a workshop with Ciaran Whyte, I decided to have a go at making a tri-flash hotshoe adapter, seeing as we made so much use of one during the day. I happen to have 3 Canon 540EZ strobes which I could use. To make things easier to mount, I wanted to trigger all three strobes with a single radio receiver. To do that, I’d have to modify my strobes to give them a sync port.

Adding sync-ports to the 540EZ strobes

The following images show the steps I went through to make the mod. First I’ll start with a before-and-after shot:

On the strobe on the right you can see the 3.5mm jack socket mounted in the red plastic window. I had to remove some parts of the strobe to make room for the socket, but since I only ever use these in manual mode, they bits I took out are never used. Undoing the 4 small screws at the bottom allows you to remove the hotshoe section of the strobe.

Next images shows the part of the strobe that we’re going to discard to make room for the sync port:

Next, we pop out the red window, drill a 6mm hole in it (I used a special acrylic drill bit I had lying around. Using other bits may crack this piece, be careful.

Next, we solder two wires from the jack socket to the relevant pins on the hotshoe. In the 540EZ, the ground is the blue, and the trigger is the red.

Red window, re-inserted, soldering all done, about to re-assemble:

All back together. You might want to test the connections before putting it all back together.

Testing the new sync port with a 3.5mm jack to 3.5mm jack cable. The Cactus V4’s have a 3.5mm jack socket on the side. Nice feature.

All three 540EZ’s complete, with new 3.5mm jack socket sync port.

The next task was to make up a 4-way 3.5mm jack plug cable, so I could connect all three strobes together to one wireless receiver:

Followed by a few quick test shots:

The 3-flash setup will give you one of two things:

  • Three times the power
  • Or, faster recycling times.

The 4-way cable saves on radio receivers.

The Triple-Flash adapter

I then took the three hotshoe/umbrella adapters I had, and thought about mounting them on the same tripod. The simplest method at hand was two pieces of cylindrical hardwood bolted together into a cross. That way I could put one ‘end’ into the tripod, and put the three hotshoe adapters on the other three ‘ends’. (oh, and I cut the bolt for a neater finish).

Twisting the strobes and adapters into the following configuration, I ended up with a pretty neat setup, all triggered off a single radio receiver.

I put set this up beside a 400W studio head I have at home. To test the power of the tri-flash setup, I set all strobes to max power and adjusted my camera until I got the histogram right. I then put the 400W head at full power, and to my surprise, the histogram was just about the same! (maybe 1/3 stop more). So, with the 3-strobe setup I’ve now got about 400W of portable power. 🙂


Extra Circuit to get Cactus V4s to trigger 3 540EZs

I was having problems triggering all three flashes with the single Cactus V4. The refresh times went to hell. One or two flashes, fast recycle time (@ 1/128 power) but with three connected, several seconds.

I recoon the problem was down to poor isolation between the trigger and the three strobes, so I designed and built the following prototype:

Shown in the above (very messy) circuit is a 3V power supply, two 3.5mm jack sockets (one for trigger, one for flash 4-way cable), a 50 ohm resistor, and a small low-voltage transistor. The theory was that when the trigger closed the circuit, 3 volts would be gated into the transistor, causing the output to short circuit, triggering the 3 strobes simultaneously. This triggering would be electrically isolated from the output of the wireless receiver, so it should recover quicker, allowing me to trigger rapidly in succession, which it was not when directly connected. At least that’s the theory. And low-and-behold, the damn thing worked. There was no-one more surprised than myself. I could now trigger all three strobes as fast as my thumb could press the transmitter test button. No delays from the receiver. Wicked. So I then pulled out an old eBay trigger that no linger worked, mounted all the above circuit into a nice neat box, and got some well earned sleep.

Here’s the enclosure showing the batteries, and input and output 3.5mm sockets.

I used the existing power switch as well, so the circuit is completely dead unless I switch it on. I’m wondering if I should integrate the transistor and resistor straight into the drigger? Might be a squeeze, but it’s one less set of batteries to be worried about. Maybe it’s not worth the trouble. Anyway, I was happy to have solved my trigger speed issue.

I’ve also tested this with a set of borrowed Yongnou RF-602 triggers. These do not exhibit the same issue as the Cactus V4’s, in that I can plug the 4-way cable directly into the receiver and it will trigger all three strobes without any  recycle delays. These must have better trigger isolation than the Cactus V4’s. No need for the extra circuit. –Edit– You can add Cactus V5’s to the list that don’t need the extra circuit.

Needs Circuit:

  • Cactus V4

Doesn’t need extra circuit:

  • RF-602
  • Cactus V5


6 thoughts on “Canon 540EZ DIY Sync Port”

  1. Well, Ciaran, you can’t say I wasn’t inspired by your workshop! 🙂

    Also, I’ve had issues with the 4-way cable, the recycle time is excessively long with all three strobes connected at once. With two, it’s fine, but three seems to slow it down. Must be the flashes connected to each other that’s causing some kind of feedback loop. I can’t remember my electronics well enough to debug it. I guess I’m stuck at using two triggers to drive the 3 strobes.

  2. I’d say it’s a loading issue more than a feedback issue? I’d suggest just using one trigger anyway and slaving the other two flashes?

    I hope you don’t mind, but I’m going to feature this blog on my own?

  3. You might be right there Ciaran. With the 4-way cable, the trigger doesn’t seem to be able to go back to open-circuit quickly. No problem with a piece of wire across the terminals, I can trigger as quick as I want. Cactus V4’s not designed with this in mind, I guess!

    Oh, and blog away!

  4. Trigger problem solved. New circuit designed and built to resolve the issue. See the last couple of pics in the article above.

Comments are closed.

%d bloggers like this: