How to make a £9.99 Airwave Vtx module work... for less than a fiver.

[stevec]

Hi All,

I needed a fatshark compatible video transmitter, and once the need was identified it was like oxygen and I couldn't live without it!

so as they were out of stock all across the planet I decided to buy the module and make the supply board for it.
here:- http://www.firstpersonview.co.uk/transmitters/5.8ghz/airwave-5.8ghz-wireless-rf-av-module?zenid=516e6358ccd2991caf91aa5175a1d974
Anyone who watches the RC model reviews YouTube videos will have heard of the FPV backpack.
this is for the other flavours of Vtx that transmit on the odd numbers. (the frequencies all end 05) This is a different pinout standard to the Airwave module so I had to make something different.

I searched some threads and did a lot of reading but there was no step by step guide.
I have a basic education in electronics and seeing as the module does the hard work I figured it wouldn't be too hard to make a similar "backpack" for the Airwave module.

anyway here is what I did.

firstly the documents that are available that support this module

DATA SHEET FOR PRODUCT

http://www.dpcav.com/data_sheets/AWM661TX.pdf


LOGICAL DIAGRAM OF BOARD

http://f1chf.free.fr/PDF/airwave%20modules/AWM651T-eval.pdf

The circuit diagram I used an LED to give an indication of power and other than that it is just the logical circuit above put down in a circuit diagram.

attached below is the circuit diagram.

Parts list.

2x 10k resistors                    MCF 0.25W 10K RESISTOR, 10K, 250MW, 5%      2p each
1x LED                                  had one in my toolbox.
1x 5v voltage regulator         MC7805ACTG IC, V REG +5.0V, 7805, TO-220-3   46p each
1x 3 switch DIP switch         A6S3102H SWITCH, DIP, 3 WAY, SEALED             85p each
1x 470uF capacitor.              ECA1CHG471 CAPACITOR, 470UF, 16V                22p each

Small piece of varoboard  £2.99 from maplin 
A strip of board header pins. £1.30 from Maplin
A servo extension lead.
an old bind plug
various heatshrink etc..
A sharp tipped soldering iron, preferably low wattage.

A cloverleaf antenna for build instructions see RC model reviews or flite test

the components were all bought from Farnell. (UK electronics retailer)

I cut the varoboard to give me 9 tracks (like the module) and then I positioned the largest components on and moved it as far up the board as I could to give me the length to cut the thing down.

I ended up with a board about 50mm square.

to work out which tracks to cut position the switch so it corresponds with tracks 1-3 when viewed from above. then under the switch module you need to break the tracks so there is no circuit. use a small drill bit and drill into the track using a hole as a guide.

the next 2 tracks (4 + 5) need to be cut in order to mount the resistors. pins 6 and 9 are left alone. pin 8 is cut so the capacitor can be mounted.
pin 7  is cut under the middle leg of the regulator, to give an in and an out side on the rail.

in order to make life a bit easier I ran the components onto both sides. the resistors LED and capacitor are mounted on the side opposite the tracks and soldered on top.

First I mounted the switch and pin headers. then the regulator capacitor LED and resistors.
then the regulator.

I soldered an extra pin header onto the video rail from the back so I could connect a servo wire to it.
Camera power is taken from the Vtx side of the rail so it is regulated at 5v.
And then finally I soldered a piece of wire from the off cut of a resistor across the GND pins All rails are connected except video out and +5v (pins 6+7) I used a small piece of heatshrink so they cant short this out.

I then attached the unit to the pins by splaying the module pins out and the pin headers in. simply solder one of them together then align the pins and get soldering.

Power is provided from a servo extension lead that connects to the Vin on the regulator and Gnd.


BEFORE YOU POWER ON !! check continuity with a meter. I hadn't broken a track completely and it was under the switch so I couldn't see it I only found it by partially disassembling the board.


so taking it all into account I spent less than £15 on a 25mw Vtx. it definately looks home made but it is incredibly small, light and can be arranged to be different shapes depending on what you are putting it on.

I found it uses the frequency at the other end of the range to the  fatshark module I have which I find useful, but I think I have the dip switch the wrong way around on mine... just hit the buttons on your fatsharks to select the channel.



Some pictures attached below.


hope someone reads this, finds it useful and has a go. it is a bit intimidating but for the sake of £15 it will keep you out of trouble for a couple of evenings... Obviously with 25mw of power it may be worth investing in some decent antennas as 5.8 ghz stuff is pretty hard to make in an optimal fashion unless you have test equipment to chack the tuning, and a three decimal place vernier to measure it out with. but for a small quad or something you are not going to go far with then it is ideal.

If anyone spots mistakes let me know and I will update..

have fun
Steve

Ps. and if my crap soldering skills can get it working then anyone can do it :P

[skyscraper]

Excellent article. Congratulations on getting it sorted!

regards
Andy

[stevec]

Thanks, I'll make a neater one when I get time...  :laugh:
A lot of the items I bought required a few of them to be bought, so I have enough parts to make 3 of them. 5 if I hardwire the channel frequency.

/Steve

[Coyote]

Why have you took your audio outputs to 100k resistors ?

[skyscraper]

Why have you took your audio outputs to 100k resistors ?

I think I suggested to do that! (If the input is high impedance then it can oscillate and add af noise into the module). Its probably fine to leave audio inputs open circuit though!

regards
Andy

[stevec]

Yup, Skyscraper advised...

obviously you could replace those with capacitors 33Uf from memory and actually use the audio circuits. but I don't like the sound of wind and brushless motors...

cheers
Steve

[skyscraper]

Yup, Skyscraper advised...

obviously you could replace those with capacitors 33Uf from memory and actually use the audio circuits. but I don't like the sound of wind and brushless motors...

cheers
Steve

You could add the capacitors  ( in fact small one like 0.1 uF would do) and ground the inputs or put them to supply if they are electrolytic. That might have been better.would be  Interesting to see which option used less current.

Would also be interesting to leave the audio open circuit and see what if anything you can hear coming out the other end!

hmm.. I have one of these lying around so perhaps I should test it rather than talking about it  :)

regards
Andy

[mark]

Bloody el i know who to look for for some techy help from now now on lol.

[FPVSteve]

hey mark, you're not the rebel who flew around the pleasure beach a while back are you?

:P It's okay, you're among friends here :D

[DaveyLC]

I use that vTX on my mQX but its single cell so only needed the bypass cap :)

[tdmodels]

Hi SteveC,

Nice project.  You can also get the modules from Active Robots if Simon runs out.  They also supply a 600mW version with heatsink  ;)

http://www.active-robots.com/radio/data-video-audio-modules/5-8ghz-av-modules/5-8ghz-video-audio-transmitter-module-1.html

[g.collins]

Nice job bud, perhaps you can put all the components in a bag and sell it as a kit, then do a youtube video instruction video.
:) G

[mark]

hey mark, you're not the rebel who flew around the pleasure beach a while back are you?

:P It's okay, you're among friends here :D

Ha no but it was on my todo list. Beaten to it lol.

[Ynot6]

done much the same for my buggy. i put mine in an ally project box, the module is clamped to it for heatsinking. i also used a bog standard 7805. the only question on that is, as my buggy is 2 cell, will the 7805 drop out before the lipo alarm goes off? linear regs usually need at least 2 volt more supply than their output voltage.

[Ynot6]

to make a good kit, an etched PCB with the correct, ie 2mm, pin spacing for the module would be much appreciated by many of us. any one on here do PCB etching?