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Let's start with a background information. Unitra ANIA R-612 is kinda old FM 'tourist' Polish mono radio produced in communist times. It was relatively of good quality both as it comes to materials and electronics circuits inside - as it received stations very good and the sound quality was good. From a visual aspect of the design it was also quite nice. It could be powered with 220V/230V and alternatively with 5x AA. It could receive LF (D), MF (Ś), HF (K) and FM aka VHF but in OIRT band 65.8-74.0 MHz. As it might be suspected FM/VHF was most popular, but in late 90s all the stations were forced to move to CCIR band - 87.5-108MHz. Finally we moved away from eastern ideas of doing things different and joined the rest of the Europe. But, this required to re-tune radios to use so called upper band. Three years ago when there was a need to have a radio in a bathroom I came up with this Unitra piece but I had to re-tune it and succeeded ... only partially - the radio covered only 2/3rds of the current band and the reception was not so much ideal (remember - it is in a bathroom - no windows and a lot of pipes - waves may have problems). Let's end up here.
The idea was to replace the old electronics with something from 21st century - there were some voices of electronics guys that new modules are much worse etc (no filtering of low gain stations) and I should try to re-tune one more time. But, I'm not really into analog electronics, so I started the project to revamp the radio with Arduino + TEA5767 or RDA5807m FM module + Nokia 5110 display. And here it is - the revamped Unitra ANIA R-612.
The aim was to keep the original look&feel of the radio as much as possible. So, I kept the volume potentiometer working also as a power-on switch. The analog feeling of tuning along with frequency indicator moving up&down had to be kept working (even though the scale is not relevant anymore due to OIRT -> CCIR transition). I could use rotary encoder for this but I felt that co-ordination with analog indicator may get lost so I decided to use rotary potentiometer which of course is not so accurate for fine tuning, plus the influence of temperature and humidity (wire connecting analog indicator) doesn't help. But, it still gives the old-school feedback, yo! To avoid madness in the household I decided to convert the band switch to do something useful i.e. to tune into 3 preconfigured frequencies, only the first position allows for free tuning.
To get any feedback what's the current frequency I decided to implant Nokia 5110 display and which was hidden under the scale. Its illumination automatically fades out when tuning is over, so it doesn't destroy the look so much. The LCD may also display the name of the radio station, but since the FM module I used doesn't provide RDS readings the radio station name is taken from the list of predefined stations. This list is also being used to automatically fine-tune to exact frequency. The LCD display additionally displays the signal level and mono/stereo status.
The radio is powered by 5x AA batteries consuming around ~56mA. Sadly, I didn't measure what was the original power consumption :/ The circuit for 230V has been removed (you don't want that functionality in the bathroom, right?), even though it could be left as it was - the LDO could have been be easily connected to the existing Graetz bridge after transformer.
More photos of the retrofitted radio running this project are here.
Here is the video how this revamped radio works now:
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Arduino Nano or similar
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- there are integrated boards like here with headphone amp, sockets and some signal amplifier - no need to solder
- if you want to use TEA5767 directly then be careful about soldering
- apparently the integrated board above in comparison with RDA5807m (see below) is able to pick up weaker stations due to signal amplification, but this introduces a lot of interferences between stations
- no RDS support
or alternatively (and I prefer this module):
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- be careful about soldering and voltage (requires 3.3V - take power from Arduino 3.3V)
- has better performance than integrated board with TEA5767 - less interferences from weaker stations
- can work in TEA5767 compatibility mode (see legacy branch)
- it has a nice RDS support
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PAM8403 amp (I use only one channel, since the radio has only one speaker)
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220uF capacitor - connect it to output of LDO
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4x resistors 220ohm
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a lot of jumper wires :)
- Arduino IDE
- Nokia 5110 library - import this library to your project
- Radio library supporting RDA5807M & TEA5767 plus SI4703/5 - import this library to your project
There is a legacy branch that used TEA5767 library here. Pros & Cons of this library:
- less dynamic memory used
- in my setup it caused sound interruptions while getting the signal information from the module
- uses floats for frequency adjustments which made potentiometer adjustments very picky
- RDA5807m worked in TEA compatibility mode with no RDS support
Of course to do it right I should have designed a custom circuit board, but since I wanted to play around and have some freedom to add new features I used universal prototyping circuit boards and everything was connected using jumpers (I guess I spent more on them than on the Arduino and modules <sic!>) and a bit of hot glue :)
The connecting scheme is mostly the same as on Nick's project with some additional wirings to:
- control LCD brightness - connect 8-LED pin of LCD to digital pin D3 of Arduino
- to quickly adjust to predefined stations using rotary switch - connect Arduino's analog pin A1 to main pin of rotary switch and between position pins solder use resistors (220ohm) to build a voltage ladder then connect the first pin to negative and the last one to positive
- in case of RDA5807m you must power it with 3.3V which you can take it directly from Arduino 3.3V PIN, alternatively add low-pass filter (60ohm + 110uF) to drop voltage from 5V to 3.3V and provide less noisy power supply for FM module
To provide 5V power out of the 5xAA battery pack use LDO LM1117 in the simplest manner (refer to its data-sheet) - simply connect GND to negative, INPUT connect thru the switch embedded into potentiometer and finally use OUTPUT to power all the stuff. To have stable 5V place 220uF capacitor between OUTPUT and GND (watch out for polarity!).
Since this project is based on this project the original licenses still apply. The modifications here and/or enhancements are being done under Apache 2 license unless the original license states otherwise.