540EZ trigger voltage

[william_tucron]

I've been using inexpensive ebay radio slaves to trigger both studio and

multiple portable hot shoe flash units for a couple of years. Apart from

limited range I've never had a problem until I recently bought a 540EZ.

 

I was quite surprised to discover that none of the 5 slaves that I have (of two

different types) would reliabley trigger the 540EZ. With the slave connected

the flash will only fire about 5-10% of the time and the firing seems to be a

random event. It's not an electrical contact problem since, if I remove the

slave and short the cable, the flash will trigger 100% of the time.

 

I finally concluded that the design of the slave is such that it's simply not

capable of reliably triggering with such a low voltage as my 540EZ. My 540EZ's

trigger voltage is only 3.35 volts when on AA batteries and 3.75 volts when on a

high voltage battery pack.

 

I borrowed a friend's 580EX to see if this was a Canon Speedlite issue but the

580EX checks out at 4.5 volts and the slave will trigger it 100% of the time.

All of my other flash units work reliably as well but all the rest are more than

4.5 volts.

 

So, can someone with a 540EZ please measure the trigger voltage of their flash

and tell me if less than 4 volts is normal for this flash or do I have a

peculiar one.

 

Chuck Norcutt

<http://www.chucknorcutt.com/>

[steve_dunn2]

<p>I don't know if that result is unusually low, but since many Canon hotshoes have a maximum safe voltage of 6V, I wouldn't expect any Canon flash to have a substantially higher voltage than yours.</p>

 

<p>There are other common issues when using slaves to trigger Canon shoemount flash units; Canon's flash units are not really designed for this sort of use and it's common for them to lock up after firing.</p>

[mark u]

I think you are suffering from SCR lockup. A specially designed circuit is needed to allow the flash to reset - otherwise you have to switch it off and on again between firings. The circuit is included in Canon's hotshoes. There are a few slave triggers that do work - such as the Ikelite Lite-Link - which is unfortunately only available second hand as it is no longer made.

[alec_myers]

I have the problem of no triggering of my 540EZ with my radio slave system (cheap one bought of Ebay) which is annoying because I bought it specially for use as an off-camera wireless flash.

 

The trigger voltage is about 2.5 volts immediately after a full discharge, climbing to about 3.9 volts after a few seconds. That's with a newly charged set of NiMH cells. My guess is the voltage starts low because the high current draw during recharge pulls the cell voltage down and the +V rail in the flash with it. It rises as the current draw decreases and the cells return to their nominal output.

 

It had never occured to me that a sync voltage that was too *low* could be the cause of the problem. I will have a think as to whether there is a simple-to-implement way to fix this.

[poulbh]

I do have a Lite-link for sale if interested.

Sorry for the spam but not OT I think.