Even Rognlien Posted November 13, 2009 at 11:46 PM Posted November 13, 2009 at 11:46 PM Hello VATSIMmers! First of all - sorry about my bad english... I'm an early ATC on vatsim and I have started a project of [Mod - Happy Thoughts]embling a real ATC/pilot-microphone with a built in PTT button, so it will communicate with my computer. You can watch my project translated by google, here (page 4 ->). To translate the PTT-key at the MIC, to a keystroke on my computer, I'm using a small program called 'CPSwitch' by Sascha Broich who made the program for his own ATC microphone. The program will read every short-circuit between pin nr 2 and 3 in a serial RS-232 9-pin, and translate them into keypresses - for example 'Ctrl' or 'Space' - that can be selected and recognised by VRC or Euroscope as a Push-To-Talk key. Works great! Here is the connection diagram of my set up (also in norwegian. 'Spenning' = voltage): My Holmco MH-50.1 microphone [Mod - Happy Thoughts]embled with a serial female plug (for PTT) and a 3,5mm jack (for voice). So.. I have a strange problem with the sound when the PTT is connected to the RS-232 serial, and the microphone is connected to the microphone input. It's like a fast, loud, ticking sound that almost drowns the sound from the mic. When the PTT is disconnected from the RS-232 (pin 2 and 3) the noise is gone, and the microphone sounds perfect. I can also mention that if I touch pin nr 3 in the serial port with my finger or something metallic, when the microphone is connected to the mic-input, the ticking starts. There is no ticking if the mic is not connected but the PTT is, and I'm using the computers internal mic. When the mic is connected and I touch pin 3 or short-circuit pin nr 2 and 3 without directly touching the thing that makes the short-circuit, then the ticking is gone. The ticking is only there when CPSwitch is running, thus when the serial-port is activated. So my question is: Is there possible to get this ticking noise away? I have got two tips, but I have not tested any of them yet: relay or opto-isolator I really hope that someone can help - if you understood anything of my english x) Will a relay work? - if so what type of relay, any product suggestions? Will an opto-isolator work? - if so what type of relay, any product suggestions? Best regards Even Rognlien Link to comment Share on other sites More sharing options...
Richard Gerrish Posted November 13, 2009 at 11:59 PM Posted November 13, 2009 at 11:59 PM OK looking at the wiring diagram vs the picture.... part of the problem very well could beyou have your Mic running into the serial where it could be getting contaminated with power from the USB and then out to the audio card where it can't be dealt with. if you're good with a soldering gun remove the 3.5MM from the serial and reconnect it directly into the XLR that should keep any power bleed/cross that could be happening in the serial connectors Richard Gerrish Developer, STM Applications Group Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 14, 2009 at 11:56 AM Author Posted November 14, 2009 at 11:56 AM Yes, that could be the problem, but I 99% sure that there is no connection between the mic and the serial port. But I have found an electronic board inside the microphone where all of the five cables are connected. Maybe they have connection inside there? I have tried to open the mic, but cant get the board out... Anyways, as mentioned, the noise also appears if i touch pin nr 3 when the PTT-is not connected to the serial port - but the noise is lower actually... Link to comment Share on other sites More sharing options...
Richard Gerrish Posted November 14, 2009 at 04:18 PM Posted November 14, 2009 at 04:18 PM true enough there could also be solder in any of the XLR connectors that could be shorting across the pins creating the buzz Richard Gerrish Developer, STM Applications Group Link to comment Share on other sites More sharing options...
Paul Byrne Posted November 17, 2009 at 01:20 AM Posted November 17, 2009 at 01:20 AM Hi Evan, Can you tell me how you have wired the 3.5mm stereo jack? This sounds like it could be a grounding issue. I had a look at the specs for your mic. It is a dynamic mic, so it doesn't need external power. The core you say is 5V power, is probably the screen (ground). If this is the case, then on a stereo jack, you would wire the screen/mic- to the sleeve of the jack and mic+ to the tip (I am [Mod - Happy Thoughts]uming that mic+ is carrying the audio). The ring should not be used. Cheers! Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 17, 2009 at 04:57 PM Author Posted November 17, 2009 at 04:57 PM In the forum I linked to, I have posted this picture where you can see how I did it: You're right, the unisulated wire from the jack is connected to the 'screen' you see in the connection diagram of the microphone. The only way I could get this mic to work, was that I twinned the white and the screen wire together (equivalent to the black and white from the microphone), and the red wire directly to the brown. Don't know why, but that worked - perfect! I'll try out your tips Paul, but not sure if it will work... Link to comment Share on other sites More sharing options...
Paul Byrne Posted November 18, 2009 at 01:00 AM Posted November 18, 2009 at 01:00 AM Hi Even, Yeah, that all makes sense with the 4 pin XLR. To explain briefly: Microphones can be wired in one of 2 ways. Either balanced, using a 3 pin XLR (each core has it's own terminal on the XLR) or unbalanced, using a jack or mini jack (only 2 terminals available to wire). There is a way to wire a balanced signal on a stereo jack, but for your purposes, it is not necessary. For unbalanced the screen has to be combined with the mic- core so it can ground the mic properly and prevent earth loops or worse an electrical loop that will shock you. Because you are using a 4 pin XLR with 2 terminals being used for the switch, this means you have to make the microphone send an unbalanced signal which makes sense when you say you have to combine the screen and mic-. You can consider this combination the ground for the mic. Now, there's one vital piece of info that we are missing. What are the specs of your soundcard? Different soundcards can sometimes use different wiring systems for mic inputs etc. However, most are Tip = Signal/Ring = Power (for microphones that need power)/Sleeve = Ground. Therefore you need to make sure that mic+ is connected to the tip and the ground is connected to the sleeve. The ring should not be used or bridged in any way. Let me know if that's the way it is wired or if it works out for you. If it's still creating that buzz, then the grounding issue maybe in the switch and may require you to try and earth the switch somehow. Cheers! Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 19, 2009 at 09:13 AM Author Posted November 19, 2009 at 09:13 AM Thanks for reply - I will try that =) But do you know what wires that goes to the differents parts at the minijack? And if that doesn't work, maybe there is possible ground it using pin nr 5? At this picture, pin nr 5 is tagged as 'Signal ground' http://www.machine-information-systems.com/images/RS232-9-pinout.gif. If so, any ideas how I can do it? Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 19, 2009 at 05:14 PM Author Posted November 19, 2009 at 05:14 PM Hmmm, looks like the only way to get this mic to work is to twin the white mic- with the bare br[Mod - Happy Thoughts] wire (both from the minijack). Maybe there is some sort of a preamp or something inside the microphone that need power - as I said, there is a electric data-card inside the mic's handle with lots of small gadgets [Mod - Happy Thoughts]embled. But I found something when I did some attempts with the 'Signal ground' pin (nr 5). When I connected pin 3 with this pin, the buzz where totally gone - but when I tried to push the pushbutton the emulation software on my PC didn't noticed it - of course x) Maybe the only way to fix this problem is to buy a keyboard emulator card with dozens of key inputs to $50....? Or anyone here with a better idea? I can see if I find an old serial joystick or something, and see how they have fixed the buzz problem. EDIT: Ahh, maybe this is what I need - a virtual RS-232 trough the ethernet port! http://www.billproduction.com/ Link to comment Share on other sites More sharing options...
Paul Byrne Posted November 21, 2009 at 05:20 PM Posted November 21, 2009 at 05:20 PM Hi Even, Yes. The white core and the bare br[Mod - Happy Thoughts] core out of the minijack should connect to mic- and screen (what you called 5V) out of the microphone. The red core should connect to the mic+. If it is connected up like that, then it is probably a grounding issue with the switch. You could try this if you wanted. On the cores coming out of the microphone. Split the screen in half and connect half to mic- (as before) and the other half to ptt-. You will be basically bridging the ground over the mic and switch. That may solve your issue. Cheers! Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 22, 2009 at 08:57 PM Author Posted November 22, 2009 at 08:57 PM Thanks Paul, tried that and the buzz disappeard - until I pressed the PTT button and it came back, now even stronger I think I'm going to try an audio isolator. Think i found one here..: http://cgi.ebay.com/MINI-3-5MM-NOISE-FILTER-GROUND-LOOP-ISOLATOR-CAR-AUDIO_W0QQitemZ370213547700QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item5632726eb4 Link to comment Share on other sites More sharing options...
Paul Byrne Posted November 23, 2009 at 02:41 AM Posted November 23, 2009 at 02:41 AM Hi, Close, but no cigar, eh? There's one more option, if you're willing to try it. Can you make the wiring from the XLR 4-pin female to the serial male use 3 core cable? Then wire the extra core to the ground pin on the serial and merge it with ptt- into the XLR? Just like you do with mic- and screen out of the mic to the XLR 4-pin male. Don't forget to remove the screen bridge to ptt- from the mic! We managed to isolate the ground until you closed the circuit on the switch (pushing the button). Sounds like you'll need to isolate the ground on the PTT from the mic ground. This may do it. Cheers! Link to comment Share on other sites More sharing options...
Even Rognlien Posted November 23, 2009 at 03:55 PM Author Posted November 23, 2009 at 03:55 PM Thanks, but if I understood your description right, I have already tried to do that - to connect the serial ground pin with one of the PTT-poles (don't remember which) while they both are connected to their pins on the serial port, and also with the PTT wires coming from the mic. It seems like that when the serial ground pin is connected with one of the PTT pins, there is not enough power left for the other PTT pin to read the signal from the other. The buzz is gone, but the CPSwitch software can't read the PTT-press. Link to comment Share on other sites More sharing options...
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