FM Transmitter Enclosure by BobP_

Last crawled date: 3 years, 4 months ago

This “Thing” is a simple enclosure for the small, low cost, FM transmitter module that I purchased on Amazon. (See link below) Similar units are available from AliExpress, Banggood and eBay. I know the enclosure will work with the dimensions of this unit and this FM transmitter made by ICstation has been working very nicely. Inspiration for this design came from the Thing :2247929 by JMadison. My goal was to have a design that was simple, easy to print successfully and work with the dimensions of the FM transmitter I received. The unit is rather small with ports and controls grouped rather close together. The enclosure’s dimension had to be pretty much “right on”.
Keeping with goal of simplicity, I went with powering the unit via the USB connector and using a length of wire for an antenna. (See the note below about using the USB for power and using the 3.5mm input for the audio). For convenience in connecting the antenna wire, I soldered a male, breakaway header pin to the PCB. A female connector was then fastened to the one end of the antenna wire. This allows the antenna to be added or removed while the circuit board is safe within the enclosure. For short distances, say 10 feet (~3M) or so, I got acceptable performance with no external antenna. This method of connecting the antenna is optional.
Again, for printing simplicity, I chose to use screws to fasten the back to the case. You will most likely have to use a 3mm (~1/8”) twist drill to clean out the printed holes in the back. The 3mm by 6mm long screws will create their own threads in the printed case.
The back has two protrusions that will hold the PCB against the front of the case. These protrusions are not symmetrical so care must be taken to position the back correctly. The antenna clearance slot in the back is the key for aligning it correctly. If you find there is excessive space between the display and the case, try adding some spongey foam or tape to get a tighter fit. If when printed these protrusions are too large, file them down for a proper fit.
Because the enclosure is so small and dimension a bit tight, check your printer’s extrusion rate so as to not over extrude. I printed everything in PLA with a 0.4mm nozzle and a layer height of 0.1mm. I will suggest that, at a minimum, the 5 buttons must be printed with a .1mm layer height. Over extrusion can make them bind in the panel opening.
Note-
OK, the note about using the USB port to power the FM transmitter. This information is based upon my experience with the referenced transmitter module. FM transmitters from other suppliers may not operate exactly the same way.
If you connect the unit to a PC via the USB and want the PC to provide the audio source it works nicely. The PC should automatically install the necessary driver and the device will show up as CD002. You can then route the PC’s audio to this device and receive it on your FM radio.
However, if you want to use the 3.5mm port for your audio input while powering the FM transmitter using USB, the USB cable cannot have any connections to the two data lines. If there are connections on the data lines within the USB cable the transmitter will switch to the USB for its audio input. This NOT a problem if you use a simple cell phone charger or similar device to supply power. If you run into this situation, the two data contacts within the USB connector will have to be isolated. I simply placed a piece of tape over the two, innermost, contacts of the USB-A connector on the cable I used to connect the 5 Volt power adapter to the FM transmitter. Also note that if there is no audio input source the built-in microphone is active by default.
The FM transmitter I used in this project is made by “ICstation” and I purchased it herehttps://www.amazon.com/Mini-Digital-FM-Transmitter-Module/dp/B01N7DIRE9/ref=sr_1_3?dchild=1&keywords=icstation&qid=1602638542&sr=8-3