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Mr.RC-Cam

HeadPlay HD Goggle Upgrade: Add 5.8GHz Diversity & DVR

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l decided to upgrade my HeadPlay HD goggles with some new features. Specifically I wanted to add diversity receivers and a DVR. In case other HeadPlay owners wanted to duplicate my DiY project I purposely selected components that are readily available. But be warned: The task requires electronic skills and a 3D printer, so it's not a project for everyone. Total cost of parts is about $80 USD.

Here's some photos of the finished project. A 3D printed enclosure contains the 5.8GHz diversity vRx and low cost SD card type DVR.

front_view1_1000.jpg

 

A toggle switch (bottom left side of photo) is used to select live video or DVR playback video.

side_view1_1000.jpg

 

The original 5.8GHz vRx board is removed (but the LCD driver board remains). A 3D printed filler panel replaces the vRx board and is used to cover-up the vacant vRx's holes.

top_view1_1000.jpg

 

The 3D printed parts help with the aesthetics. It's a bit boxy looking, but the simple 3D printed shapes ensure successful printing on nearly any printer. I used ABS filament but PLA will work too.

And the best part is that you can remove the mods and restore the goggles back to their original configuration. The only evidence of it would be five small holes from the mounting screws. Nice!

 

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Document Area. Skip to the next post to continue reading about building the project.

If you have any questions about these files (or any other details) then please do not PM or email me. To promote information sharing I kindly request you post your HeadPlay Diversity project questions in this open forum discussion. Thank you for your cooperation!


SCHEMATIC DRAWING SECTION

schem_icon1_400.jpg Schematic: HP-DIV_Schematic_Basic.pdf

 


BILL OF MATERIAL SECTION

Bill of Materials (BOM) for DiY buffer board: HP-DIV_bom.pdf
Note: If external video option (see schematic) is used then add R5 and C3 to the BOM.

Eachine DVR-Pro: https://goo.gl/N6BHcy
Note: The latest version (V1.6) does not work well (black screen on weak signals). The older V1.4 hardware version works correctly. Before you place your order it would be wise to ask the supplier which version they are shipping. Be sure to upgrade the firmware with the latest release.

RX5808 Pro Diversity: https://goo.gl/uUgsNI
Note: It is offered with RP-SMA or SMA, your choice. Choose the version that matches your antenna's connector.

M3 Brass Inserts (5 pcs): https://goo.gl/m7GJ9g

M3x14mm (1 pcs) and M3x30mm (4 pcs) countersunk screws: https://goo.gl/vHOVSU

M2x12mm (4 pcs) self tap pan head screws: https://goo.gl/OPio6C


STL FILE SECTION

All STL files should be rescaled to account for your filament's shrinkage. For example, I use 101% scaling with my ABS.

Use your best judgment on choosing filament/print settings. If you are new to 3D printing then here's some basic recommendations:
Main Enclosure & Filler Panel: 25% infill, no supports, 3 shell layers
Screw Mounts & Clamps: 45% infill, no supports, 4 shell layers

The Main enclosure has some supports already included in the STL file. After printing they need to be removed; Please see this post for details: Click Here!

stl_enclosure1_500.jpg Main Enclosure: div_enclosure_revA_bin.stl

 

stl_clamp_set1_400.jpg RX5808 Pro Board and DVR Clamp Set: div_clamp_set_revA_bin.stl

 

stl_screw_mt1_400.jpg Screw Mount Set: div_screw_mount_set_revA_bin.stl

 

stl_filler_pnl1_400.jpg Filler Panel: div_filler_panel_revA_bin.stl

 

 

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The two main components are the GE-FPV branded RX5808 Pro Diversity board and eachine proDVR V1.4 module.

div_dvr1_800.jpg

The DVR has all the cables you will need for this installation. But you will need to supply a micro-SD card.

The diversity board includes the OLED display and buzzer. It is available with SMA or RP-SMA connectors, your choice. No cables or antennas are provided.

Keep in mind that the diversity board is based on a open source project. So an endless number of Chinese suppliers have created their version of it. They are not all the same! Besides firmware variations, they can differ in board shape/size. If you choose the one shown in my source links then its shape will be compatible with the 3D print STL files I have created for the project.
 

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Regardless of the diversity board version you use, they all suffer from an inherent design deficiency. And it isn't just the RX5808 Pro that has this issue; The other Chinese copies of this "open source" 5.8GHz diversity design have it too.

The problem is that the raw video signal from the two 5.8GHz receivers is routed through a 74HC4066D (4066) analog switch IC. Unfortunately this simple circuit doesn't ensure the composite video signal can properly drive the monitor with industry standard video amplitudes. Instead, the signal level (amplitude) is too low, which results in reduced amplitude sync signals.

Let's step back for a moment. Why should you care so much about the video signal's level? Because marginal video amplitude can cause intermittent video sync problems during weak RF signal events. This invites the dreaded weak signal blackouts we all hate. The whole point of adding the diversity feature is to improve our video experience, not add another point of weakness to it. So stay with me, there's a solution.

Here's copy of a typical RX5808 diversity schematic I found on the web.

rx5808-pro-diversity-schematic.jpg

The 4066's signal path to the monitor is shown in the schematic as VIDEO_BEST. Those of you that are familiar with composite video designs should be able to recognize the issue with the 4066 directly driving a common 75 ohm terminated monitor. Hint: The 74HC4066D has ~50 ohms on-state resistance.

Not to worry, the Diversity Pro's video level has been corrected in my HeadPlay HD project. All it takes is a video buffer circuit. Fortunately it's not too much work to make things right. After all, we want the best possible image in our HeadPlay goggles.

And the DiY video buffer is also used to restore the eachine DVR's video level to standard amplitudes too. Out of the box it's output video level is incorrect (a common problem on many Chinese video designs).  The output level on mine was 10% too low. The buffer I built fixes that too.

Here's another DVR related benefit of the buffer circuit. Without it, the DVR will stop recording whenever the Live / DVR switch is used to change the video source. But because the buffer maintains a constant 75 ohm termination on the DVR's Vid-Out during the switch's transition, the DVR is tricked into staying in the record mode. Cool!

Edited by Mr.RC-Cam
Updated info.

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A small piece of proto perfboard is needed to build the video buffer circuitry. None of the components are critical. The 470uF caps need to be small so they can fit inside the enclosure.

Here's a look at the basic components I used (trim pot not shown):

parts1_1000.jpg

4 pcs, 0.1uF 50V Ceramic Cap
4 pcs, 75 Ohm 1/8W 5%
2 pcs, 100 Ohm 1/8W 5%
1 pcs, 200 Ohm trim pot
2 pcs, 470uF 10V Electrolytic Cap
1 pcs, THS7314 3-Channel Video Amp IC (SMD).
1 pcs, DPDT mini Toggle Switch
 

The THS7314 IC is only available in a SOIC8 SMD package. I used a SMD to 8-pin DIP adapter board for easier mounting on the perfboard.

smd_dip1_800.jpg

 

It's a good idea to dry fit the perfboard in the 3D printed enclosure before adding components. Cut its perimeter so that it is about the same size as seen in the photo below.

dry_fit1_1000.jpg

 

Component placement on the perfboard is not critical. I highly recommend a generous use of connectors to allow for convenient servicing. For example, the photo below shows how the toggle switch and buffer board combination is plugged into the DVR and Diversity board.

cable1_1500.jpg

 

Here's what it looks like after installation in the 3D printed case:

assembled_inside1_1000.jpg

A bit messy looking but everything fits!

 

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And speaking of the 3D printed case, here's an explanation of how all the printed bits go together.

After printing the enclosure you'll need to trim out the support structures blocking the DVR (SD card side) and at the RX5808 Pro menu switch. The supports to be removed are shown in the red regions of this photo.

clamp_main1_1000.jpg

 

Four M2 x 12mm self tap screws are used to hold the 3D printed Diversity board and DVR clamps. See photo below.

clamp_main2_800.jpg

 

After printing the top and back screw mounts you'll need to heat-set five M3 brass inserts. The inserts go on the side with the larger diameter hole and must be flush with the plastic part's surface. See photo:

brass_inserts1_1000y.jpg

My brass insert mounting technique is [1] heat them for five seconds on my soldering iron, [2] push them in until nearly flush, [3] immediately (while still hot!) press the face of the part against a flat surface for a flush finish. Be sure to clear out any plastic residue by threading a M3 screw into each brass insert.

The screw mounts go on the inside of the goggle's top foam case. After locating their positions (by dry fitting the plastic enclosure), cut away some foam around each screw mount post (shallow cuts, do not penetrate to other side). Set the plastic pieces down into the foam for a recessed fit. See photo below:

screw_mount1_1000.jpg

M3 screws are used to mount the 3D Printed enclosure on the goggle's top foam case. You'll need:
4 pcs M3 x 30mm Flat Head machine screw
1 pcs M3 x 14mm Flat Head machine screw

Use a countersink drill bit to bevel the exterior screw hole openings for a flush screw head installation. See photo below.

case_screws1_800.jpg

WARNING: Do NOT use longer screws than specified or the LCD will be damaged!


 

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Of course before you install the new plastic enclosure you'll need to wire the buffer board to your goggles. Remove the LCD driver board and solder the buffer's four "LCD1" port wires as shown in the photo below:

lcd_pcb1_1000.jpg

Yellow: Video
White: Audio
Red: V+ (Battery Voltage)
Black: V- (Common Ground)
Note: These four signals are shown on the schematic at reference LCD1.

Lastly, there's a trim POT on the buffer that is used to set the video level from the RX5808-PRO. Set it mid-position as a preliminary adjustment on first use. Later you can tweak for best overall image under all camera lighting conditions. Ideally you would use an o-scope to calibrate the POT for a perfect 1vPP level (full white amplitude).

 

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That wraps up the project; Diversity and a DVR are very nice additions to have on these goggles.

 

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This is very helpful. One question, how did you disconnect the original video receiver from power, or to the LCD?  Thanks.

Edited by Northernflyer

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The cable that connects the old HeadPlayHD receiver to its LCD board was unplugged. Both the cable and receiver can be saved in case you ever need to restore the goggles back to the original (factory) configuration.

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Thank you for the excellent mod! I want to upgrade my own Headplay to Diversity but without the DVR option. Do I need the video buffer board in this case? Instead I thought I simply can connect J1 from the RX8508 (VCC+, GND,Video_best, Audio_best) to the LCD driver board (where the RangeVideo RX was connected to).

I am running my Headplay with 2s lipos but on the RX8508 I can see 3s-4s power input. Do I need any stepup board to 12v in order to run the diversity?

Do I miss something? Any comment on that is highly appreciated :)

 

Regards

Andreas

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1. The RX5808 Diversity board will function without the buffer circuitry. That is how everyone on the planet (except me) is using it. However, the video levels will be out-of-spec (reduced amplitude). This will increase video drop out events during weak signals. I care about getting the best video performance so I recommend fixing this issue by installing the buffer circuit.

2. The DC-DC switcher supply module mounted on the RX5808 Pro does not tolerate 2S (causes noisy images at the low voltage). You could either use a step-up supply or replace the existing 5V step-down module with one that will work correctly on 2S.

 

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Great project!

I am wondering if you would consider selling a set of the 3D printed components.  I can handle the electronics but will have difficulty with the case. 

Thanks

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Thanks for the feedback. I've had several request to print my 3D parts. Unfortunately I'm swamped with other projects and don't have time to do it. However, there are hobbyists and businesses that will print any 3D part for a fee. I don't have any recommendations, so just put google to work.

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1 hour ago, Mr.RC-Cam said:

Thanks for the feedback. I've had several request to print my 3D parts. Unfortunately I'm swamped with other projects and don't have time to do it. However, there are hobbyists and businesses that will print any 3D part for a fee. I don't have any recommendations, so just put google to work.

I understand.  I will look into other options for the printing.  Thanks again for the instructional post on the diversity option. 

 

1 hour ago, Mr.RC-Cam said:

Thanks for the feedback. I've had several request to print my 3D parts. Unfortunately I'm swamped with other projects and don't have time to do it. However, there are hobbyists and businesses that will print any 3D part for a fee. I don't have any recommendations, so just put google to work.

I understand. I will look into other printing options.  

Thanks again for the instructional post.  I'm looking forward to having diversity in my Headplays. 

One more question.  Have you looked into using the LaForge firmware with your system?

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Have you looked into using the LaForge firmware with your system?

I haven't tried alternate firmware. My HeadPlay goggles are for random spectators & guests; They don't need the cool features found on the LaForge and other variants. My favorite goggles (DiY 3D printed) have a Diversity Demon (Oracle) on the ground station to handle the diversity switching. It works great.

The stock firmware is Ok, but needs some tweaks to the RSSI switching functions. But from what I've seen from other firmware versions of the Diversity Pro they all tend to switch too slow for my tastes. It seems the developers like a lot of RSSI signal averaging and they add some debouncing (switching delay) to it too.

For agile drone piloting I prefer super fast diversity switching to mask multipathing events. It might not be possible to do it well with traditional RSSI based diversity, but it certainly could be better with some code tweaks (hint: less averaging and less debouncing).

- Thomas

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I am wondering if you can comment on whether a receiver such as the Laforge or Furious could work with the Headplay.  

I don't know enough about the electronics side of this to know whether it would be as simple as using the pin-outs on the other receivers to connect them to the Headplays.

I would appreciate any input that you could offer.

Thanks,

Guy

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The various RX5808 diversity boards are all based on a similar electronic design, but have different physical shapes and firmware. I don't have any experience with the variants, but I would expect that using them with HeadPlay is possible.

 

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You mentioned that the Chinese diversity units are often different, so I understand if you don't have an answer to my question.  The diversity unit I purchased http://www.ebay.com/itm/112065477304?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT lists power suppy as 3.5v-5.5v.  I am assuming therefore that I will need a voltage regulator.  I am guessing that I will also connect your buffer circuit to the same regulated 5v.  Is that correct?

Either way thanks for coming up with this setup.

Kingdon 

Edited by Kingdon Humann
misspelling

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I am assuming therefore that I will need a voltage regulator.  I am guessing that I will also connect your buffer circuit to the same regulated 5v.  Is that correct?

Yes, you will need a 5V VReg that can handle about 1A.

Quote

Oh, and can you give a link to the buzzer you have installed.  Is the low voltage circuitry internal to the buzzer as I do not see any in the pic.

My diversity board included the 5V magnetic buzzer. There is a large silkscreened circle (about 1/2" diameter) on the PCB that shows where to install it.

 

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