Pupil-Trainer cord for Futaba-MPX combination

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=82 BGCOLOR="#006699" TEXT="#080000"> <div> <FONT SIZE="5" COLOR="#FFFFFF" FACE="Arial" ><B>JBVM Delemarre</B></FONT><B>     |    </B><A HREF="id49.htm" TARGET="_top" TITLE="This is the English part of my home page"><U><B> </B></U></A><A HREF="index.htm" TARGET="_top" TITLE="JBVM Delemarre"><U><B>home</B></U></A><A HREF="index.htm" TARGET="_top" TITLE="JBVM Delemarre"><U><B> to the Dutch start page</B></U></A><B> </B><A HREF="id49.htm" TARGET="_top" TITLE="This is the English part of my home page"><U><B>  home to the English start page</B></U></A></div> <div> <B>Pupil-Trainer cord for Futaba-MPX combination</B>   |   <A HREF="id100.htm" TARGET="_top" TITLE="Circuit and PCB design for the FutabaMul"><U>Circuit and PCB design for the Futaba-Multiplex Trainer cord</U></A>   |   <A HREF="id103.htm" TARGET="_top" TITLE="The Connectors"><U>The Connectors</U></A>   |   <A HREF="id104.htm" TARGET="_top" TITLE="Parts list for the FutabaMultiplex train"><U>Parts list for the Futaba-Multiplex trainer cord</U></A>   |   <A HREF="id102.htm" TARGET="_top" TITLE="Pictures of the Futaba Multiplex trainer"><U>Pictures of the Futaba -Multiplex trainer cord</U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=100 BGCOLOR="#FFCC66" TEXT="#080000"> <bR> </td> <td valign="top" height=398 BGCOLOR="#FFFFFF" TEXT="#080000"> <div> <I>Pupil-Trainer cord for Futaba-MPX combination</I></div> <div> Recently, Ian Stockley-Miles from England, posted a question on the MC-4000 list on the internet concerning the option to give tuition to a pupil using a Futaba transmitter as the pupil transmitter and a Multiplex transmitter as the teacher transmitter. Although a quick investigation learned that the outgoing signal from a Futaba TX is a positive baseline with negative pulses, which is the same as Multiplex, a simple coupling of both transmitters did not work out all right. An interface, adjusting for the voltage levels, also did not bring the solution. The problem was that the servos showed a "wobble" in their positioning with a frequency that proved to be the same as the difference between the frame rate of the Futaba TX and the MPX TX. Even when only the ground potentials of both transmitters were connected and the Futaba transmitter was switched on but without it's RF module in place, this problem showed up. I did not understand how this was possible but it made me search for a better solution. I wanted a complete isolation between the two transmitters so an optocoupler had to be included. This came down  to some experimenting and soon a working circuit was devised on my expermentersboard.</div> <div> On the input side there is only one transistor as a buffer from the circuits in the Futaba transmitter driving the led in the optocoupler. The supply voltage for the input side is derived from the Futaba 's DSC socket together with the signal needed.</div> <div> The output side is driven from the Multiplex transmitter taking the voltage needed from the middle pin on the left-hand socket on the TX side.</div> <div> The output from the optocoupler is amplified and inverted to get the signal needed for the Multiplex transmitter. I used a 5 volt regulator to get a five volt peak to peak signal as is normally seen on the output of the Multiplex TX in pupil-mode. I don't know if this is absolutely necessary but it was easy to do and didn't need any experimenting.</div> <div> When the prototype seemed  to work without any problem, even when maximal interference was tried to induce by placing other transmitters on a different frequency right over the circuit, a PCB was designed and the definitive prototype was produced and tested.</div> <div> Together with the tryout version this can be seen in the picture below.</div> <bR> <div> <IMG SRC="2058f880.jpg" border=0 width="655" height="392" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> Only a slight modification on the output side was made and the circuit and PCB design for the definitive version are presented herewith so you can also make this rather simple but effective piece of equipment. I had some correspondence with Ian Stockley-Miles from England in the past concerning the RPM sensor for the MC-4000 and he initiated this project so I did give a PCB to him with a rough description and a drawing so he could make the cable. He tested it with various types of Futaba transmitters and found that it did what it was asked to do. He kindly gave permission to mention his name as the "independent field tester" for this interface.</div> <bR> <div> August 15th 2002 Ian send me an e-mail with the following message:</div> <bR> <div> Hello Hans , </div> <bR> <div> I have tested , the Mpx lead with 3 Tx's yesterday (wed 14th) , it works fine! </div> <div> It was tested on two FF6's and a FF7.tested on an irvine trainer , and two thunder tiger trainers. </div> <div> A friend of mine at the club who has a MPX 3010 , is interested in a lead and i am making him one. </div> <bR> <bR> <div> <A HREF="id100.htm" TARGET="_top" TITLE="Circuit and PCB design for the FutabaMul"><U>Circuit and PCB design for the Futaba-Multiplex trainer cord.</U></A></div> <bR> <bR> <bR> <bR> <bR> <bR> </td> </tr></table></body>