Retrofitting an FM radio with Arduino


Instead of throwing out a defunct radio, this hacker decided to have some fun with an Arduino. 


10 years ago, Marcus Jenkins purchased an inexpensive Sunstec RP-S500 FM radio. Left with an obsolete, malfunctioning device, the hacker decided to take its inner workings and convert them into an Arduino FM radio.

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The radio, which appeared to be something straight out of 1975 and not 2005, was pretty bad at tuning. Aside from that, the Sunstec RP-S500 had some trouble finding stations and keeping it on without drifting off. After taking one look at its mains, and it was obvious that it was not the most well-engineered machine ever made. Meaning, any effort in trying to fix it would be useless.

Instead, Jenkins decided to have some fun with an Arduino and retrofit the gadget. His primary goals? To make it work more like an old-school car radio, hold on to a set frequency and be loud enough to hear around the workshop. Channeling his inner DIY spirit, he drew up a simple schematic that employed an Arduino Nano (ATmega328), a TEA5767 FM module and an LM386 audio amplifier.

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The Arduino is connected to a microswitch with 1k pull-down and the FM radio via I2C. Meanwhile, a single button on the board helps cycle through a range of preset frequencies stored in memory. The TEA5767 module, tasked with outputting the audio, was attached to the radio’s existing antenna, an Arduino and the audio amplifier.

“The LM386 circuit is pretty standard – I had a 10u gain setting cap and a 10k pot on the input for setting the radio volume to ‘loud but not distorted.’ The 9V and 5V rails are decoupled with electrolytics and smaller mylars,” Jenkins writes.

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He kept the Sunstec RP-S500’s original tuning knob, though no longer functional, and fitted the old AM/FM selector with a microswitch linked to the Arduino. This would enable him to switch between preset channels. Everything was held together with what Jenkins calls “hot-snot glue.”

Impressively, the entire project only cost the Maker $1.50, as everything was recycled from items lying around. Interested? Head over to its detailed post here.

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