Isolated DMX splitter

Introduction

When you need to connect DMX projectors you can use wireless or cable. In my case, I have a fixed setup so I use a wire solution. But the problem with DMX is the low immunity regarding disturbances. When a connexion is lost in the chain all the projectors after the losy connection are out of control. I already have spiltted the DMX in branches. To do that, we use an isolated DMX splitter. In this case, when a branch brockdown, all other are still working. On the other hand having an isolation between the projectors and the command avoid ground current. And to conclude, the splitter also helps to regenerate the signal over long distances.

This small post presents you a DIY solution for a 3 way DMX isolator. I use components I have in stock as the case, the RS485 and the NE555.

The schéma

Explication

The power supply

The power supply is really simple. A 7805 for the 5V regulation so we can connect USB, transformer ;on it. The isolation is performed by a DC/DC converter MEV0505. I just add the LC filter as recommanded in the datasheet to avoid noise

The DMX Bus

The splitter doesn’t decode the DMX. A receiver is an the input to convert the differential signal into a TTL level. We use a MAX3082 to do that. The signal is than forwarded to 3 isolated RS485 driver ISO3086. This driver is isolated so you need to apply power suply on both sides.

LED

I add an activity LED to visualize the activity on the bus. The BREAK on the DMX bus trigg the NE555 and the LED is ON. but it doesn’t work correctly when nothing is connected and when the receiver in high state is.

The box

I had an EUROBOX 135x95x98 box in stock. It’s huge enough for the PCB and the connectors. I used the 3D printer to have a front panel and the back panel who fits to the connectors.

Manufacturing

PCB assembly

 

Front and back panel

Box integration

PCB and the front and back panel fits to the enclosure. No screws requested