Intro: FTDI USB Adapter Based DMX Transmitter With Isolation
Discovered by accident, when I had a FTDI USB to Serial adapter plugged in while using a DMX program and noticed that it was seen as an Enttec DMX USB transmitter device. After some research on the topic, I started with a simple SN75176 with a female DMX receptacle, it worked well so I developed this isolated version described here.
Utilized similar isolation as the USBDMX.com hardware. Found a few other sites that built similar USB DMX transmitters, http://fritzing.org/projects/arduino-to-dmx-converter/ and http://openschemes.com/2011/06/17/homebrew-usb-dmx-interface-with-sparkfun-ft232rl/
Total cost depends but about: $15 for FTDI board, $7.50 for DC/DC isolator, $6 misc = $28.50usd
Works with Freestyler and MADRIX for sure, but many other programs should be compatible as well.
Step 1: Supplies
- FTDI USB to Serial Adapter, tested with FT220XS-R and FT232R, others may work as well. Such as FT232RL
- SN75176 - RS485 transceiver, DIP
- NKE0505SC - DC/DC isolator
- 6n137 - Opto-Isolator, DIP
- 0.1uF disc capacitor
- 10kohm 1/6w resistor
- 2k2ohm 1/6w resistor
- 1kohm 1/6w resistor
- LED, 3mm or 5mm
- 2x 8-pin DIP sockets
- Plastic Enclosure, I used a power supply case
- Some perforated board, 2" x 2" at most
- Not used or shown, but a panel mount mini USB to Type-B would have been useful.
- Soldering Iron and Solder
- Wire stripper and pliers
- Tools to make, cut, drill the case
Step 2: Assemble
Tested the 2 kinds of FTDI Chips, other types should work as well. I am assuming any that identify as VID 0x0403 & PID 0x6001 would work the same. As both the ones I tested that work used that VID and PID
Schematic explains it all, it is pretty simple to do it point to point on some perforated board. Used the kind with copper traced rows. With a good layout it required minimal jumper wires and cut traces. Should be fine to test it before putting it in a case.
The NKE0505SC and the 6N137 fully isolate the USB FTDI adapter and computer from the transceiver and the receiving devices on the DMX circuit. Protecting the computer and USB adapter from shorts, noise, and other problems. While still being powered over USB.
Case: Used a 2 part plastic case that was for a inline DC power supply
- Removed any electronics from it
- Figured out how the electronics will fit, the FTDI board should be mounted so the mini USB jack can be accessed from the outside, for this I stacked some plastic blocks up so the FTDI chip'd USB jack sat in the middle.
- Drilled a hole from the outside of the case that is big enough for the USB plug to fit into.
- Figured where to and cut a hole for the female panel mount XLR jack. Which is usually 7/8"
- Drilled holes to mount the panel mount jack's screws.
- Drilled a 5mm hole for the TX LED
- Inserted all the electronics, hot glued the FTDI board in place with the USB jack accessible from the outside.
- Closed it up.
- Lastly threw some decals on the case to make it more recognizable, since it looks like a power supply.
Step 3: Usage
So far the device has been tested with Freestyler and Madrix 2.0(version 3 didn't detect it) but many other software is listed on the Entecc website.
Few thoughts: The micro USB jack that comes on most FTDI chips isn't that strong, which could be an issue if it is heavily used. Maybe a FTDI adapter with a USB Type B jack would be better suited. This worked so well for many projects, since it can also transmit regular serial over RS-485, that a revised version is planned. Mostly the same electronics design but, bi-directional capability and jacks.
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