Relay: start an HMI ballast by DMX.

ballast 2K5 HMI

We will practice what we saw with the 8 relays board tuto.

ATTENTION ! As always with the devices in 120/230V, it is necessary to be extremely careful. Always unplug the device before opening it. Even when disconnected, beware of capacitors that can remain charged!

The context

The Surnatural Orchestra uses in his show Esquif a Fresnel projector 2.5 KW in HMI. The lamp requires to be started before each representation, and to be cut at the end of it. A big green button and a big red button are there for that.

boutons du ballast

The problem is as follows: the projector and its ballast are arranged at 12m high ... So it was necessary to climb before and after each show.

We will remotely start it, with relays, driven in DMX by an arpschuino board.


* We have no agreement with the mentionned companys, images and links are just provided as examples.

Set up

There is not much room inside the ballast to integrate the arpschuino and the relays. We decide to use a 2 relay card. Its operation is identical to that of the 8 relay board.

carte 2 relais

Since we can not install our adapter as easily as on the 8 relay board, we will connect it with cables.

adaptateur modifié

Integration of electronics

It is necessary to secure our boards. Despite the size of the ballast there really is not much room in there!

intérieur du ballast

The apschuino is placed under circuit-breakers, and the relays above it. Then we drill the ballast enclosure to the size of the arpschuino XLR (22mm) with a large drill bit. Measurements should be taken with care and drilling is done with the drill press.


Edit: there is now a template to help you, it is available in PDF and in DWG


Since there is not much room for integrating and fixing the power supply inside the housing, a hole is also drilled for the plug-in terminal block. After a few adjustments to the file, the arpschuino finds its place, screwed on nylon spacers.

l'arpschuino intégré dans le ballast

It's look like that :

XLR sur le ballast

The 2 relay board finds its place above the circuit-breakers, screwed on the indispensable spacers. We can now connect the board to the arpschuino. The relays are wired in parallel with the red and green buttons.

carte 2 relais fixé au ballast

the source code

The source code arpschuino_2X8relayswas uploaded into the arpschuino with just a small change to have a fixed address (400). Turning circuit 400 to more than 50% should start the ballast and mount the 401 should switch it off.

Happy of the work accomplished, we plug all and there, catastrophe, nothing works as planned! The ballast start before to receive DMX, turning the circuit 401 at more than 50% have no effect !

Let's try to understand. The contacts of the relays are closed at level 0 and open when they receive a voltage of 5V. With arpschuino_2X8relays, there was no initialisation (it's fixed now), so the relays remained closed until they received DMX.

And the red button ? Testing it with a multimeter, we can see that it is normaly closed,In other words, his behavior is reversed. The default position of the second relay should be closed, at low level in the code. Vous me suivez toujours ?

In the setup, after initializing the GPIOs as OUTPUT, the first circuit is set to HIGH and the second circuit is set to LOW.

code source

If we leave the red button, witch is normaly closed, in parallel with the second circuit-breaker, the circuit will stay closed all the time. It must be eliminated or better placed in series rather than in parallel.

This is a shematic sketch :

shematic sketch

Let's try ?

The whole (ballast and the arpschuino power supply) have to be pluged before to switch the circuit-breakers on. Nothing happend before to plug the DMX, it's OK. The DMX pluged, all the circuits at zero, nothing hapend to, OK again.

Let's put the circuits 400 and 401 at full : The lamp switch on ! let's put the circuit at zero : the lamp switch off.

Yeh it's work !

The projector on

The source code can be found hier.

We could have integrated the arpdress board to be able to change the DMX address, perhaps a next step.

This tutorial concerns of course a particular case but it highlights the problems of integration of electronics and source code modifications.

Thanks to Philippe Bouttier from Surnatural Orchestra.

We are interested in your comments and questions, please contact us: