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DIY Spek DSM2 / DSMX JR Module - For my Taranis & Horus

by dmyers7, published

DIY Spek DSM2 / DSMX JR Module - For my Taranis & Horus by dmyers7 Apr 9, 2014
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Summary

I started with using an OrangeRX module to fly my Horizon and DSM2/DSMX equipped RC aircraft. With it not being FCC certified, only operating at 100mW (as opposed to 200mW) and not able to offer full integration into my Taranis radio for features like model match, binding and range test from the radios menus, I wanted more. So I bought a DX4e from Ebay to harvest the true Spek radio module.
After testing tonight, I get quicker resyncing after drop outs (simulated during range testing), greater range than the Orange module (no dropouts even at 50 paces), model match to prevent accidental use of the wrong aircraft profile, and fully integrated bind and range testing from the software menus (no manual button presses). DSM2 and DSMX worked flawless and require no manual mode switching to achieve. (6-29-2014 You can run all aircraft in DSMX mode from the Taranis and the module will automatically drop back to DSM2 for those receivers that require it. This is what I do now).
After test flying today, I found that there was next to no latency since there is no middle step of decoding a PPM stream (as in a traditional plug-in module) just to re-encode to DSM2 or DSMX since the Taranis is talking directly DSM2 or DSMX to the transmitter module; this is a big Plus +++. I'm loving on this mod.
After some time and 20-30 flights later, the latency difference is definitely noticeable, in a good way (i.e. shorter to instant). It is noticeable mainly when performing 3D flight, but definitely noticeable. If you are flying patterns and light aerobatics a straight PPM type module would most likely be just fine, but if throttle punching and full stick precision aerobatic flight is your thing, this mod is for you. (You are not always chasing the movement of your model and stopping the maneuver too late because of the lag in stick to servo). Enjoy :-)

Instructions

My apologies, my friend who is building one noticed that I had the ground pin connection to the Tx module illustrated wrong on the schematic. Image updated. The ground wire belongs on pin one (which is the pin that has a square box as the solder pad).
As with everything experimental, proceed at your own risk and accept all responsibility for moving forward with these instructions. I can't promise this will work. I am enjoying the benefits at my own risk.
The printed parts have support designed in, do not turn support on.
Harvest the DX5e module from the DX4e unit. This has been verified to be a guaranteed 6 channel transmitter unit. Some have said that it will transmit up to 8 channels depending on the internal firmware (I can't verify as all my receivers are 6 channel max). (I will be using FrSky equipment for all things greater than 6 channels.)
I also harvested the 220uF cap from the DX4e
Do not use the 3.3V regulator from the DX4e as some websites suggest, it will brown out. I fully tested it on the bench and it failed miserably for how I planned to use it (I will be installing a 3S LiFe Tx pack which would kill the 3.3V linear regulator). Use a HK 3.3V ubec (Part # UBEC3-3v3a); you will be very happy with the results.
For the leads to connect the module to the connector in the bay I used circuit jumpers for project boards I purchased from Amazon (http://amzn.com/B00BQA5BWU). The antenna and antenna coax lead can be purchased from Aloft Hobbies (2db antenna & 70mm coax lead). I harvested mine from my orange module for now.

1-26-2016 Added two files to the .stl list for a friend looking to build an internal module for the Taranis Tray style transmitter X9E which requires a reduced profile unit and a blank lid. The antenna wire exits the side wall and gets mounted directly in the transmitter case wall. For the normal Taranis build do not bother to print the short case and blank lid. Also be aware that these two files are still a work in progress until this note is updated. Fully expecting this to also be required for the Taranis Horus transmitter X12S.

4-25-2014 - Before starting, line the bottom pocket (below the shelf where the Tx Module will sit) with tin foil and tack in place with some welders, foam tac or similar glue; the hot glue may be too thick so I would not use that. I coated the tinfoil with kapton tape to strengthen it and electrically insulate it. The tin foil acts as an RF shield to keep the electronic noise from the 3.3V HK regulator from getting into the audio circuit. MAKE SURE the tin foil is secured so it does not move and short your circuit and that any exposed solder joints do not come in contact with the tin foil. It works amazingly well, enjoy.
All parts fit into the printed module with no issues. I hot glued the 3.3V module and ferrite core down and then placed my PCB containing the components shown in the schematic onto the shelf and hot glued that down to prevent movement and abrasion of wires. You can see my setup in the photos. Ask questions if needed. These instructions assume you have some knowledge and experience building circuits like this.
Some websites would suggest you can use any diode for the 1n914 shown. I would suggest you keep to the 1n914 as this is the appropriate part for this application. It is a high speed small signal device where other diodes are built for different uses. They may work, but I would hate for you to find out that they don't always work. The 1n914 can be purchased in packs from Radio Shack for next to nothing.
Resistors are also from Radio Shack. I show a 22ohm resistor for the LED. I am using a Blue LED that runs at 3.1V. Other colors run at different (and lower) voltages and require you to adjust the resistor value so you do not burn it out. You can also see how bright mine is (and that is half brightness) so again adjust to your liking. I like to light my feet at dusk :-) My wife bought me a bunch of LED christmas strains after christmas for next to nothing. Now I have oodles of LEDs of all colors. I chose blue for this. Radio Shack obviously has these also. The hole is for a 3mm LED. Use the printed LED spacer and center it so it lines up with the hole in the lid (test fit).

4-27-2014 - When routing the antenna wire from the transmitter module to the lid, make sure your wire "flows" in graceful curves as much as possible. DO NOT bend the wire in hard turns, crease, pinch, ball up the extra, ... Any sharp turn in this type of wire will reduce your range. (I promise this information is accurate. I knew this as an Engineer, and proved it by accident the second time I put my module together. I did a range test, and then rebuilt it a third time to great fan faire.) The basic reason is that the wire is a micro coax and any sharp turns or pinching changes the characteristics of the wire causing the power to the antenna to be reduced. I route my antenna wire down the left side, around the LED standoff, across the face of the Tx module and into the lid. (Which also brings up, be gentle when you install the antenna connector into the lid; do not crease the wire coming out of the antenna and it should not have to bend at a sharp angle.)
The last item is to insure you have a drill index with multiple sizes to choose from. As you should know, the printed holes are great, but for real precision you need drill bits. I have the 115 piece set from HF. I used #1 x 3/8 SS machine screws for the corner screws and purchased them from my local Ace Hardware. This required a very accurate hole to insure the screws tapped in and did not split or strip the hole. Also clear the holes for the transmitter pins that slide into the module and test fit.
Enjoy.

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Oct 17, 2016 - Modified Oct 17, 2016

The TX case and TX lid do not mate up to each other. am i printing the wrong combination of parts? this is for a Taranis.

I've printed several and never had an issue like that. The lid is made to overhang the edge on purpose if that is what you are referring too.

Ok ignore me lol. I'm stupid.

I don't know if it was just my printer but I would suggest that you make the tabs used to release the module from the bay a little bit wider so that they overhang the edge more. This would make easier to pull out of the bay. It also may be that I am using it in a Turnigy 9X; the geometry may be slightly different that the Taranis. Thank you. It works great!

The module does not fit it the Taranis x9e.

Can you post some pics. I do not have one of the tray styles and image the same will hold true when the Horus X12S is released into our hands. If you want to mail it to me..... I can make a custom mod and print

Jan 22, 2016 - Modified Jan 22, 2016
rcbebo82 - in reply to dmyers7

Hi, i will take pictures. The problem is that the pins are much more longer then on X9D and also the clamps are too high the case of the module goes not down enough!
I'll get back with pictures this evening!

Jan 22, 2016 - Modified Jan 22, 2016
rcbebo82 - in reply to rcbebo82

Here we go,
on the first pic you see the module (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module-Pins.JPG). The module box got stuck at PIN1 and PIN4. On the following pics you can see how this looks in the Taranis X9E Slot (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20with%20Long%20Pins%20-%201.JPG, https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20with%20Long%20Pins%20-%202.JPG, https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20with%20Long%20Pins%20-%203.JPG). After that i drilled the Pins 1 and 4 a little bit deeper an edited the case the result looked like this (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20-%20Edited%20-%201.jpg). Now the case slides a bit deeper into the slot (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20-%20Edited%20-%202.JPG, https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20-%20Edited%20-%203.JPG).
I got an old Graupner 35Mhz module case which fits in perfectly. It is 3mm lower like the diy case just take a look at These pics (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20Comparsion%20Graupner%2035Mhz%20-%201.JPG, https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Module%20Comparision%20Graupner%2035Mhz%20-%202.JPG). But note it would be possible to make the case 3mm lower but i dont know how much material is at the bottom of the case an there must be also an cut out for the pin header.

I'll look a little closer at the pics when I get home. Is there a back cover that goes over the module when install unlike the x9d which plugs into an open bay? Did you clear all the pin holes with a drill bit? We can lower the profile if we take the pins out of the housings and make the holes in the case sized for just the pins.

The backplate of the Taranis case covers the module completly. The upper plate of the module case cant be used because it is too high. An easy plate would do it!
No, just Pin 1 and 4 must be drilled. I think if i sand down the back 2.5 - 3mm it should get in. I will try that if you can say me how thick the bottom is!

The bottom of the case is 2mm thick. The area where pins pass through at it's lowest point is 7mm thick. So I see that the black plastic header around the pins needs to fit inside the printed case. I can upload a version with that area cleared. Do you have a set of calibers to measure how much further the side tabs need to move down to lock in. I notice that the printed case appears to have tabs at the same height as the DIY module case but he DIY module case has lower sides, can you measure with a caliber how much lower the sides are on the DIY case. If we pull the pins from their supplied housings, will that provide a low enough connection to clear the back case? I can update the model (shrink the holes) for just the female pin and provide insulation between the pins. Let me know how I can help modify the design to work.

Well not only the pin header has to fit, there are also some other connection cable headers which are higher. See the marked areas at this pic (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/Taranis%20X9E.jpg). If you take up the bottom of the case by 2.5mm it would fit in. So the side has to be a full lenght of 19mm. Well it would be not enough to pull the Pins because the other parts are also too high, i marked that in picture one.
The antenna Output is just at the top of the taranis case see here (https://dl.dropboxusercontent.com/u/13465738/TaranisX9EModule/AntennaOutput.JPG)

Ok, two new .STL models have been uploaded. A short back (reduced by 2.5mm) and a blank lid. The top surface of the case has also been reduced by 2mm so when the blank lid is on it will be flush with the ears. There are exit channels for the antenna wires. Give that a try and let me know what you find and we can continue to develop the design to work.

Anyone could print me the new case? Ive order three of the old cases at a online 3d print service. If anyone needs one just write me a message. Im located at Germany!

I can certainly print and ship from US but if there are changes it would be faster turn around if you can find a resource local. Let me know.

Ok, let me play with it a bit today and I will upload a new model shortly. Things are going to get tight in the package. You may need to use a different regulator to power the transmitter (They certainly make smaller ones). I'll also make a flat lid and exit holes for the antenna lead top and bottom of the case. Once we have it working I would appreciate some pics to post to a new posting. I'm guess for those of use waiting for the horus to be released we are going to run into an identical setup so good to get ahead of it. Thanks for your inputs.

Will measure it in a bit when I get back to my computer. What happens to the antenna cable and antenna?

Hi there, thanks to your guide I was able to make this with a DX5e module. I am building another one with a DX7s module but cannot get it to bind to anything, any help would greatly be appreciated. Thanks.

The DX7s module has a different pinout and requires a different protocol talking to it since it is 7 channel. OpenTX is not setup to talk to it and therefore would require custom code and compile once you get pinout correct.

Dang it, wish I had do some research before purchasing it. Thank you very much for info.

Hello,
I have a Orange DIY module for my futaba 7chp can the firmware be updated I haven't installed it yet but my radio is a mode2and I have read that the channels are not mapped, I would like to use it for the sol prepuce to bind n fly. Does anyone know if there is a way to upgrade the firmware I don't see any type of socket so Im not sure if its even possible with the DIY version. If anyone can help I appreciate it. Thanks

This may be what you are looking for: http://www.hobbyking.com/hobbyking/store/__38395__OrangeRX_USB_Firmware_Update_Kit_for_JR_Futaba_Style_Transmitter_Module.html

The DIY module is suppose to be upgradable.

Of course, channel order is not a real issue unless you are trying to bind to a Horizon BNF model with AS3X. Otherwise, just adjust your servos and esc connectors to match the channel order being put out by your Futaba radio.

Hope this helps.

Thanks for the info

thank you , excellent work

Your welcome, glad it is working for so many people. Still loving on mine. My latest project involves binding a total of 22 channels of output using two Frsky receives bound to the internal transmitter and one Spektrum (orange) receiver bond to the external DIY module simultaneously. 3 receivers active in all with telemetry coming back on one of the Frsky receivers to boot.

Comments deleted.

Thanks for this also note that DX4 also have the same RF modules as DX4E and DX5E :)

The one thing that I do want to note for everyone out there wanting to perform this mod, please insure that the transmitter you cause to hack (dx4-dx6) is a true DSMX transmitter. You can tell by simply looking at the front panel. It will say DSMX compatible on it. If it does not then it is an older transmitter that is DSM2 compatible only and may not work as described here.

Apr 30, 2015 - Modified Apr 30, 2015
skelator - in reply to dmyers7

acording to spektrum website DX4 is DSM2/DSMX compatible, plus the RF modules I haversted from DX4 are the same exact modules came from DX4e and DX5e

http://www.spektrumrc.com/Products/Default.aspx?ProdId=SPMR4440

In the bottom right hand corner of the label image you linked to shows the "X" for DSMX so I agree. To further refine my thoughts, over the weekend I was looking for a DX5e for a friend on eBay and noticed that there are two versions floating around in the used market, the older DSM2 only units and the newer DSMX/DSM2 compatible units. So to others that read this comment thread, don't purchase the first thing you see on eBay without first checking the posted images.

Thanks for making this ! Do you know if there's a model of the JR reciver bay floating around as well ? It shouldn't be that hard to craft from scratch, but I figured I would ask anyway.

-=dave

The receiver bay of this module? I can pretty quickly draft that up and post if you need one. What's the project?

I want to build a bay that will except JR modules that will hang off the back of my DX9 and connect to the PPM output port on it. I already have an EZ-UHF JR module so that's what's driving this. I'll incorporate a 2S battery and regulator into the bay.

-=dave

Would love to help with this. Do you have 3D CAD skills? There are a couple obvious things we need before starting.... We need to model the other parts you want to include. I have 5V regulators & 2S batteries from HK, but this might not be what you have. BTW, I would suggest using a LiFe pack instead of a LiPo just in case you over discharge during use. Keeps it safer. Let me know how I can help.

My modelling skills stopped progressing after finishing my Autocad class back in school, and let me just say that was on DOS :-p

I've recently started playing around with Sketchup, and Fusion 360 (I think I'm going to invest the time to learn 360). My plan was to try and mash up the receiving bay (if I found one), along with 2x 18650 Li-Ion cells (I've got a ton of them: http://www.thingiverse.com/search?q=18650) into the case that hung off the back of the DX9, likely with Velcro or a combination of Velcro and "hooking" underneat the horizontal bar. You can see the general idea in my last PPM adapter here: http://www.rcgroups.com/forums/showpost.php?p=28218702&postcount=1350

My goal is to create an actual JR-compatible module bay that will take whatever I want to plug into it (at which point, I'll probably print out one of your cool module cases and transfer my Arduino based Hubsan PPM adapter into :)

Let me know what you think, or what traps you could see me easily falling into.

Thanks for your interest !

-=dave

Feb 11, 2015 - Modified Feb 11, 2015
dmyers7 - in reply to fiveangle

I'm with you on the general concept; thanks for the links. In the next day or two I will start a new thing in progress and we can build from there. Standby,

Cool ! Even something half started would be useful for me, since I'm otherwise starting from scratch.

Thanks !

-=dave

Feb 21, 2015 - Modified Feb 21, 2015
dmyers7 - in reply to fiveangle

Posted as a Remix to the DIY Spek Module, the first test print is ready for you to try. See if that works for your other modules and then we can go from there to design the electronics bay, upper flange and any surrounding container. Start posting comments to the new thing comment area as we move forward.

dmyers7, Thanks for the project - it was great. I just got my Taranis last week and I'm planning on making this DSMX mod. I have a few questions that I am trying to answer while I try to locate a DX4/5 for cheap. I'd like your opinion...
1) Is the LED just for show, or does it serve a purpose?
2) To keep RF noise down, could a linear voltage regulator (UBEC) be used instead?
3) You used tin foil as a RF barrier - does this need to be connected to ground or is it just a shield?
4) You indicated that it is not good to use the 3.3V regulator out of the DX4/5. Would you advocate building one from scratch with a different source, or in your experience is the UBEC adequate and preferred?

Dec 17, 2014 - Modified Dec 17, 2014
dmyers7 - in reply to HilldaFlyer

Answers:
1) Yes, Just for show. Although there is a practical use. The Taranis only applies power to the module port when it is activated in the menus. So, if it is not lit when you expect it, you know to chase a problem or at a minimum check your setup. An easy way for quick troubleshooting.
2) The switcher certainly has the possibility of generating RF noise, but the bigger culprit is the RF module itself. If you turn your transmitter on while in an aluminum case with the spek module enabled you will most likely hear the RF in the speaker pretty loud. Moving the spek antenna around will change the RF interference. You could use a linear regulator, I did not since there is no cooling vents and a linear will dissipate more heat because it runs considerably less efficient. Volt drop current draw" or 1.7V * 300mA? = 0.51W (1/2w) [mA is a guess, I don't have the measurement written down].
3) Believe it or not, Aluminum Foil works well. A ground connection would help the foil absorb the RF, instead it reflects it away from the radio / audio amp. Other items can be used like copper tape; just make sure you cover it to prevent shorts. Aluminum in and out made a measurable difference.
4) The UBEC has been working great and provides more than enough current by a large margin. The linear regulator in the DX4/5 does not have enough capability to supply regulated current and goes into thermal shutdown, ... not good in the middle of a flight. (That's why I fully tested it prior using it.). You can design your own, just make sure you have fully checked it out before using it at the field with others around that could be hurt if something goes wrong. If thermally a linear regulator is getting hot, remember on a hot summer day it will be getting just that much hotter (constant rise above ambient temp). Make sure it won't enter thermal shutdown which will cut power to the transmitter module until it cools enough. In other applications, I have thermally glued linear regulators to machined blocks of aluminum as a heatsink in an enclosed area and it has worked very well, .... so it could be possible. Just be careful and test fully so you don't loose that 12ft wing span B-17 mid flight. (I know, you'll be using a 16ch Frsky receiver in that model :-)

Enjoy, Here's to great flying and safe landings

I followed your schematic. Got good power,led comes on, taranis set to dsm2/dsmx. just wont bind. Tried on blade 130x and on orange rx. Nothing will bind. Did you have any of these problems. I did notice that your schematic was different than a couple of other pages.

Dec 7, 2014 - Modified Dec 7, 2014
dmyers7 - in reply to soccentzulu

By the way, the DX7 is a DSM2 only transmitter. Assuming the pinout of the module remains the same as the 6ch one, setting the protocol to DSM2/DSMX in the Taranis would not work. You need to set it to dsm2/dsm2. The Taranis firmware is also currently limited to 6 channels without a custom compile.

So I did some more research and found that the DX7 transmitter module shares the same part number as the ones we harvest from the DX4e-DX6i. The pin outs are the same so you should be fine with the supplied schematic. But, the firmware in the module is different and only supports DSM2 protocol. Try setting the Taranis to DSM2/DSM2 and see if you get a bind.

Dec 5, 2014 - Modified Dec 6, 2014
dmyers7 - in reply to soccentzulu

Did you use the module from your DX7 or from a [DX4e, 5e or 6i (all the same)]?

To answer your question directly, I built one for a friend a month ago from the design as posted so yes it is correct. Let me know how I can help.

Thanks for the Calculation. From the range tests (50-60 paces) and the very long distances I have flown my planes (sailplanes) the power output has not shown to be an issue at all. The receiver has never shown a drop out (no blinking light on landing). Mine has seen hundreds of flights at this point with zero issues. Thank you to the openTx software crew for a fabulous firmware that allows us to do this. (Donate to their effort if you have some extra.) Enjoy :-)

Nice! I'm building one.
Note: the Spektrum module used has a -18.31 dBm (68mW) power output. This is slightly less than the OrangeRx's claimed 100mW, and considerably less than the power output of many higher end Spektrum radios.

Sep 18, 2014 - Modified Sep 18, 2014
dmyers7 - in reply to abobotek

Just made another for a friend and walked to 80 paces on range test to an Orange receiver before drop-out; I would say that is plenty full range. If you need any further than what that equates to not when in range test then you need to switch to UHF long range module. Spektrum (c) prescribes 30 paces in range test to test distance, so I say this is more than decent; especially when you consider the quickening roll off (decreasing) of the signal strength as the distance increases. It's never skipped a beat on my Spek module, and I've been some distance at times. Continue to enjoy.

Great! I made a similar DIY Spektrum module for my Taranis and am also having very good results with it. I'm using a 3.3V series instead of switching regulator to avoid RF emissions at the expense of efficiency. I got lucky with an eBay Spektrum transmitter purchase; its module puts out 92mW. This is slightly more than the measured output of my particular OrangeRx module. But 92mW is still far less than what my Spektrum DX-7s or Taranis emit. My 3D printed mechanical design is slightly different from yours, placing the antenna a few cm higher and farther from the handle. I now happily use my DIY Spektrum module with OrangeRX aircraft except when I need 7+ channels from the OrangeRX (the low end Spektrum module is limited to 6 channels).

Unless you compile a custom firmware, the OpenTx firmware only supports 6 channels to the Spek module. That and no one in reality is going to open a DX7s or 8 to steal a module for additional channels. At that point it makes much more sense to use the FrSky receivers if you are using a Taranis; which then offer telemetry back and higher transmission power. For those that are not aware of it and downloading this design, yes it only supports to a max of 6 channels transmitted to a DSM2 or DSMX receiver; that is a limit in the hardware modules we repurpose and the firmware as compiled.

I will be attempting this mod using the tx from a dx7. Will i still be limited to just 7 channels? Im just using it for PNF helis and such...nothing too big. Dont see a need for more than 6 channels; just curious about the limitations.

The Taranis is using a custom firmware (part of the standard Open Source project) that limits the channel count to 6 and no more. To increase this you would need to modify and recompile a truly custom firmware for upload into your transmitter. The module in the DX7 is different then the module used in the DX6i and below. What I do not know but suspect is that the DX7 and above modules will require a different protocol then what the Taranis is currently program to communicate; because of the higher channel count.

My suggestion would be not to hack into your DX7 but instead sell it on Ebay for some good cash, buy a DX4e from Ebay, and pocket the difference for a new model or parts. You are sure to have it working at the end of the day. The module in the DX4e provides 6 channels transmitted from the Taranis.

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