How many radios are in a radio? FM 87-108 MHz RDA5807S do-it-yourself kit

What kind of soldering kit for a beginner? The HU-017A kit shown here costs just under a dozen zloty, and you can get it even cheaper in a promotion. It allows you to build a simple FM radio based on a ready-made RDA5807S module, a microcontroller with a 7-segment display for tuning and a TDA2822M audio amplifier. A slightly more expensive version with an enclosure is also available.

Let's start with the contents of the kit. I got mine in a promotion, I paid about 10 PLN. Let's see what's inside:

Loudspeaker and antenna you know, components and board too, but they even gave a battery basket and USB cable. Not bad.

The seller has thought of everything - there is even a bilingual manual. For this reason, I will shorten my argument a little here, but will still present the assembly of this radio.

I always start by wiping the board with isopropanol. Any dirt or grease makes soldering difficult. Hygiene of the soldering iron tip is also important, but the board should not be forgotten either.

Most of the components are assembled by threading, although there are a few sparse SMD parts. It's best to start with the tiniest circuits, then the soldered ones won't interfere so much with the assembly of subsequent ones.

The smallest is probably the 74HC595D sliding register. It allows you to control the display with fewer pins on the MCU side. I discussed it in a separate topic .

It must be fitted according to the marking of the first pin (dot/cut). My method of soldering is to apply solder (and always a little flux - for convenience) to one pad, then "grab" the chip by one leg, and solder the others. It is important to heat the pad and apply the binder to it - not directly to the soldering tip.

The second thing that needs to be soldered at the beginning is the radio.... or rather the radio module - the RDA5807S. This is the one that receives the radio signals and converts them to audio output, tuning is done digitally via I2C protocol from the microcontroller. Here I have a similar method and again, you need to take care of the correct orientation, you can't solder 180 degrees inverted.

Right next to it you need to solder the LDO that supplies it with 3.3 V, taking 5 V as input. It is also important to have good contact between the component and the large pad, which acts as a heat sink, although in this particular case there is not much heating.

Then one by one - the resistors. You just have to verify them with either a barcode or a multimeter. You can't get the values wrong, here we have two different ones, 10kΩ and 510Ω.

Of the SMD components, there is still the USB socket, or rather, its contacts are surface-mounted and the legs are threaded.

With electrolytic capacitors and transistors you also need to take care of polarity.

Finally I also solder the bases, here again taking care of the orientation, although for the base itself it is a purely cosmetic matter, however a reverse soldered base would be misleading. Then I dogleg the legs of the components (MCU and amplifier) and put them in the bases.

Still remains to solder the speaker (I take the wires, pads and solder), mount the antenna and it's time for the final verification of the solders and connections. Just for the record - the radio works straight away.

At the end we will quote the schematic of the device:

The radio from the HU-017A kit consists of several simple functional blocks. The power supplied from the USB or DC socket is stepped down and stabilised by the AMS1117-3.3, which provides 3.3 V for the electronics. The main controller of the unit is the STC8K17 microcontroller, which operates the buttons, display and communication with the FM tuner. Station reception is carried out by the RDA5807S module, which receives the signal from the antenna and, via the I2C bus, is tuned by the microcontroller. The current frequency is displayed on a four-digit 7-segment display controlled by a 74HC595 shift register. The audio signal from the tuner goes to the volume control potentiometer and then to the TDA2822 amplifier, which drives the speaker. Pushbuttons allow you to change the frequency and control the radio, and an LED indicates power to the unit.

So what is the problem with this radio?
Basically none - just buying a "do-it-yourself radio" at some point I'd expect more of a DIY radio receiver, probably still with a coil to be wound (or at least soldered on), and here we essentially have a ready-made FM tuner and solder only its control and amplifier. Only is this really a downside?
The project itself is undoubtedly trivial to get up and running, requires no tuning and will work out of the box. Just right for a beginner's first start.
Did you also assemble your own radio as part of your electronics learning, and if so, according to which schematic?