I'm confused and a bit frustrated, would appreciate any help as I'm not sure how to proceed.

Setup: I have a pixhawk autopilot running Arduplane 2.77, using Mission Planner 1.2.95

I've been following this guide to get my CHDK enabled camera working with my pixhawk. I'm interested in getting the camera triggering based on distance traveled.

Obviously the guide was written with APM in mind, so it needs to be adapted a bit for pixhawk; specifically the setting for RELAY_PIN. I've kept the rest of the settings the same as in the tutorial.

Pixhawk has 6 AUX ports according to the quick start guide, I am assuming that the numbers above the pins correspond to the AUX port numbering. When you mouse over the RELAY_PIN parameter, it says that pin 54 corresponds to Pixhawk FMU AUX1.

Tried setting RELAY_PIN to 54, no joy. Did a bit more looking, discovered in the release notes for 2.77: 

"Improved relay code
The relay and servo set code has had a major overhaul, with up to 4 relays now supported for MAVLink control and much better support for the DO_SET_SERVO, DO_SET_RELAY, DO_REPEAT_SERVO and DO_REPEAT_RELAY MAVLink commands. Along with these changes is a new parameter BRD_PWM_COUNT which allows you to specify how many auxillary PWM outputs to enable, with the remaining outputs being available as digital relays. This allows you to re-assign some of the aux servo outputs on Pixhawk for use as relays, by setting the RELAY_PIN, RELAY_PIN2, RELAY_PIN3 and RELAY_PIN4 parameters. The pin numbers for these pins start at 50 for the first aux servo pin, and go to 55 on Pixhawk."

Additionally,I found this github issue about this same problem that states that the Pixhawk can't trigger CHDK because its relay pins operate at 3.3V instead of 5V.

So i suppose my specific questions are:

1) Is AUX1 pin 50 or 54?

2) Can anyone confirm that the relays, when working properly, won't be able to trigger CHDK?

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Thanks Rob ..

I have found some tiny relays avail in 500ma contact rating and 6ma coil rating .. also some 1amp contact rating and 16ma coil rating .. It might be easier for people to use these to make their trigger cables.

see compared to a mini relay and a servo plug.

I did also find this on page 92 ..

seems its true the I/O pins can only take 25ma max.

I'm sorry Reuben, work fine, I made a small mistake! ;-)
The problem is with my Sony Alpha 5000 and the multiport connector, all is ok but with the plug connected it's impossible to navigate in the menus of the cam.
The shots makes them perfectly but if I want to change some parameters i've to disconnect the plug from the multiport, and it is quite annoying.
I haven't tried with the new circuit that you have proposed, one that performs a switching the ground and not on + 5V... what do you think?
Dunno if others have experienced with this problem.
The aux pin (3.3V signal) work with a little current, so don't overload this digital output.

Hi Marco ..

Good that it is working! Are you using my old circuit ? using PNP ? switching 5v.

Do you know the max amps on the 3.3v aux pins ..can it be as low as the suggestion of 25ma?  I thought it should be higher maybe i am wrong .. Any way i did find a nice micro relay with 16ma load on the coil so it should nice with digital relay output direct. then it can be used for many function ..camera trigger .. lights . bomb drop etc ..Lol 


Why you don't use a simply transistor in combo with a 5V relay, same as chdk circuit?

Useful info for Sony A5000 and S2 Multiport connector:

The circuit that
I posted on the fist page works perfectly with Sony ILCE-5000 and similar (using multiport connector), and it doesn't work with all the other with single transistor.
Anyway the cam remains in a kind of "lock status", you can't access any menu when the multiport cable is connected to Pixhawk, although it's not powered.
I'm trying to figure out how to fix this thing because it's really boring.
Between the two pins (focus and shutter, joined) and ground there's 3.3V, the cam throws out this voltage.

Tested with A5000 and A6000, same result.

That's a very nice info... i have succesfully built your circuit and trigger it using canon's chdk. Now i'm moving to sony a5000. Which s2 pin should i connect to your circuit? I believe the ground stay to ground, which pin goes to the signal?

Hi Marco,

I'm using your circuit to trigger A5000, when I plug the S2 into camera, it's start shoot for once and keep auto focusing (with red led shine constantly).

Then I put it on Manual Focus and was able to shutter for 3 times only with TX switch / shutter trigger and after that the A5000 just "hang".

Have you change any setting on the camera?

Or I'm missing something here..

Here the S2 multiport pinout:

 0 0 0 0 1 1 1 1 1 1  
6 7 8 9 0 1 2 3 4 5
\ /
1 2 3 4 5

USB connection:

01 VBUS (+5Vin, max <2A)
02 D-
03 D+
05 GND

Multiport connection:

06 +3.1V (LANC_DC)
07 res.
08 res.
09 res.
10 res.
11 Focus
12 Shutter
13 n.c.
14 GND
15 res.

Stranger, the first shoot is normal, but not the auto focusing with the red led shine costantly.
The camera setting is not important, how you have connected gnd / focus / shutter to my circuit?

@opiq, +1 many thanks, I've tried your method on my Ixus 100 and pixhawk and it works great, like the rest of us I have been using the ground and either signal or +5v connections I never thought of trying just the +5v and signal connections, great discovery.

@ Martin and Reuben, need we be concerned about a brown out or damage to the pixhawk via the signal connection from a large load, are the loads involved here not pretty low?

I think a servo could cause a brown out just as likely as a camera or any external device that interfaces with the autopilot.

There would have to be something seriously wrong with the camera, a short for example, to cause a brown out.

Take a look at this post --> http://chdk.setepontos.com/index.php?topic=294.msg27540#msg27540

You are just turning on a transistor with about 0.44mA of current.

If anyone is still worried about frying their pixhawk after reading that post then you can contact me and I'll sell you a switch that incorporates an optocoupler and 4 AA batteries.

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