Blackmagic Tally and GPI for ATEM
you guys are way too cool.
You should add the actual lights and power supply for the tally kit, and CHARGE MORE MONEY, so I don't have to run around to buy all this stuff. But it works, and works great.
I've been running the interface with one of our TVS units since last November, and you're right: the tally indeed works very well. It's worth pointing out, though, that the GPI portion of the interface doesn't actually do anything -- at least with the Television Studio. That's a pity, because being able to assign GPIs to various panel functions would be incredibly useful.
Would you guys mind sharing the details of your GPI and tally setup?
there is not much too it. There is no documentation from Blackmagic - it's all silk screened on the Blackmagic Tally and GPI box. You use a 25 pin male connector for your hookup. You need to be able to use a soldering iron.
I hooked up a cheapo 12VDC power supply to some LED modules we found in a surplus store - the resistor for the LED was already in the module. the LED module just had red and black wires coming out of it. We plugged in the 12VDC power supply to make sure the lights lit up. (LED's are +5VDC, so this module was configured to accept a 12V DC signal.). We extended the cables from the LED module that lived on each camera with a cable, back to the switcher electronics lived in the control room - this is also where the Blackmagic Tally box lives (it hooks up to an ethernet port - we have a cheap switch in the control room for the Blackmagic switcher, the tally box, and the computers running the ATEM).
I soldered all the black wires (ground) of the LED modules to the tally points on the 25 pin connector (as shown on the silk screen of the Tally and GPI box). I tied all the red wires together, and connected this to the + of the 12VDC power supply. I connected the - of the power supply to the GND of the 25 pin connector (as shown by the silk screen). That's it. Plug in the power supply, and switch away - and the lights light up on the camera.
Had I spend more time, I would have used a larger box with a barrier strip with screw terminals to make everything neater - but I was in a rush, and threw this together, and it worked wonderfully.
There are really two issues to tackle: first, how to connect physically to the BMD adapter; second, how to create a practical tally light.
First, the connections: while you can certainly connect directly to the 25-pin D connector, many people find a screw terminal easier to use. Phoenix Contact makes an adapter that has a 25-pin male connector and a numbered screw terminal for each pin. You can get it from Digikey (http://www.digikey.com), and their part number is 277-2010-ND. You will also need a short male-to-female 25-pin cable to connect this to the BMD box; Digikey's AE9865-ND will do the job, and is two meters long. The adapter and cable together come to less than $65, plus tax and shipping, and give you easy access to every pin without soldering... and this makes it easy to add other wiring later without disassembling the D connector.
Now, for the light itself. The relays in the BMD tally interface can't switch a lot of current, so incandescent lamps are probably out. LEDs are the most obvious alternative, but don't come with convenient provisions for mounting or connection. More important, you don't drive LEDs directly from a voltage source as one would with a traditional light bulb; you need to provide current limiting, usually in the form of a resistor that you size to produce a certain amount of current (10 milliamps, say) given a certain source voltage.
An easier solution that we are using comes from NAPA auto parts: it's an LED truck marker light that runs from anything from about 8 through 16 volts, is easy to mount, and has all of the necessary current limiting built in. You just treat it like any ordinary light bulb. Their part number is LIT 2150, and the whole thing costs less than twelve dollars. You will find two wires on the back: one has a free end, the other is connected to one of the screw holes. You will want to disconnect (cut) that second wire so it isn't tied to the mounting screw.
The last piece you need is a 12-volt DC power supply -- Digikey, for example, sells a wall-wart made by CUI that will drive as many of these truck lights as you want for under $8: their part number is T983-P5P-ND. You just need to cut off the barrel plug on the end of the zipcord. One of the two wires will have some sort of marking on it -- often a stripe -- so you can tell them apart. If you have a meter handy, you can check which is positive and which is negative; if not, I find that usually the striped wire is positive on CUI supplies. Connect the negative (unstriped) wire to pin 25 on the adapter, and set the positive wire aside for a moment.
For each truck light, just run a single pair cable -- even audio wire will work -- from the tally adapter out to the camera (or whatever). At the light end, connect the wire that had been the ground (screw hole) to the black wire in the cable, and tie the longer wire (positive) to the red wire. Back at the tally interface, connect all of the red wires (light positive) to the positive wire from the power supply; a small wire nut will do fine. Connect the black wire (light ground) to the appropriate tally output from the adapter: TALLY 1 is pin 23, TALLY 2 is pin 22, TALLY 3 is pin 21, and so on; TALLY 8 on pin 16.
All this is actually a lot easier than it sounds, and you can tally all eight sources for somewhere around $150.
Thank you both for the great info and detail! Really useful for guys like me who don't have much electronics knowledge!
this is a great description ! It's a shame that Blackmagic does not offer a "turnkey" kit that they can sell ! People would buy it.
I learned a long time ago - if you can buy it or make it, its much easier just to buy it.