This simple On Screen Display uses a board intended for use with a drone or quadcopter. The project was devised by Mike Stevens G7GTN and published in issue 12 of CQ-DATV.
Video quality from the finished item is excellent and ideal for use with amateur TV output. You should understand output is monochrome and single page.
Two PCB's are used in the project but only one is permanently installed, the other is used for programming. Unfortunately there are no mounting points on the OSD board so a little fabrication is required if you plan to box it up. I soldered some push pins to the grounds on mine and soldered the other end of the pins to copper clad board. If you want to run from the shack 13.6v supply a tiny regulator board can be added. See picture.
Out of the packing the OSD board is pre-loaded with a font set suitable for aircraft use e.g. an artificial horizon, not useful for amateur TV. Mike has provided a font set which can be downloaded and installed using the Arduino IDE software and a simple to use terminal programme. All instructions and software links are available on the CQ-DATV site so I will just outline my build.
Before you connect up the board there is a small amount of soldering needed. The OSD board has two isolated sections. At one end video output at 12v and at the other digital input at 5v, the 12v input feeds a 5v regulator which we are told is prone to overheating. For this project the two sections are linked and run with a single 5v supply. There are link points on the board so the alterations are a five minute job with the right tools.
Digital input to the board is serial so the second board you'll need to source is an FTDI USB to Serial interface. These are cheap as chips from eBay; mine was less then £3.00 delivered. Most will come with a set of leads. Beware as some Chinese sellers advertise as FTDI and supply an alternative which in my case didn't work.
Pictured is the genuine board which is only required during programming. Mine can be re-attached if I want to make changes.
Prior to boxing up; the parts cost less than £10 and it worked great. I built two of these with different talkback frequencies; a paged unit is planned using several boards in one enclosure.
OSD with no video input. Monitor TV is under a shelf causing some shading at the top.
Links. Working at time of writing. There are other suppliers for the hardware.
Due to a back problem I've been stuck at home for a while. I already have nuts and bolts in the lower back but now another disc has failed.
That's the best excuse yet for spending time in the shack; but what to do?
There were a few ideas in the BATC magazine which appealed to me and another in the CQ-DATV mag. At the time the ADF4350/1 devices were catching attention and a couple of interesting projects were submitted to CQ-TV. The first was an Arduino controlled ADF4351 development board project submitted by Alain Fort F1CJN. The ADF chips are a wideband synthesizer with Integrated VCO. Developments boards are available on eBay for about £20 at the time of writing.
Alain supplied the C++ code for the project and it was something quite new to me. Reading through the lines there were some similarities to the Basic language I learned back in the early seventies. Initially I bought the Arduino and the 1602 LCD shield. The LCD shield incorporates up/down/left/right and a couple more buttons for enter and reset. Programming the Arduino with Alain's code went smoothly and I was pleased when the LCD lit and displayed the correct menu items.
My ADF4351 board eventually arrived from China and I rigged a breadboard to test it in conjunction with the Arduino. At this point it should be pointed out that a resistive divider is used between the 5v digital signals from the Arduino and the 3.3v input to the ADF4351 board.
Again things went smoothly and I had RF output from the 4351.
Up till this point I hadn't considered housing the boards so started a search for an Arduino enclosure with space for the development board. I was amazed to find there's hardly anything to enclose an Arduino board let alone any extra space. It hadn't occurred to me that people generally use the Arduino for experimentation and therefore don't use posh boxes.
Then I remembered seeing an enclosure when I bought my Pi camera; a push together Perspex box. I wasn't sure it was big enough but ordered one figuring if it wasn't I could use it later for something else. At this point I think a reveal is in order.
Now anyone who knows the 1602 LCD shield will know that the six buttons are recessed some 6mm from the face of the display. At this time the penny dropped and I realised the display can't be fitted in the enclosure. This was confirmed when I found a small packet enclosed containing six buttons and a small PCB upon which to mount them. The only display which would fit is a 1602 serial display.
I'm slightly edgy at this point because it now occurs to me that Alain's code is written for the parallel display only. Anyway it's obvious from the display pictured above that I was able to hack the code and insert serial drivers. There was a slight setback when the I2C address of the display was different to that in the driver pack.
Eventually the ADF4351 board was mounted outboard at the back of the enclosure. It was probably a good thing as it was properly screened in a separate tinplate box.
If I had workshop facilities with pillar drill and metal folding tools I'd love to have a made a decent enclosure; but hey this is a workshop tool with frequency coverage from 34.5Mhz to 4.4GHz and it'll do for me.
You can find detailed information for this project through the BATC