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.
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
LOGICAL DIAGRAM OF BOARD
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.
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. the Capacitor is bent over on its side and the legs insulated with heatshrink.
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.
I 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 check 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..
Ps. and if my crap soldering skills can get it working then anyone can do it
Hi guys one of the chaps on an FPV forum I go on drew up a nice dual sided PCB for manufacture by OSH park http://oshpark.com/ they fab boards for prototyping etc...
The resultant PCB is fantastic and has lifted the project to a new level. The file is available here http://www.filedropper.com/immers5v
the price is reasonable and the quality is great.
Thanks to Roger from FPVhub for the drawings!!