Introduction: DIY FM Radio
Video footage of assembly and testing it out!
Step 1: FM Radio
Radio's have always been a mystery to me since I was born. Magical signals that can be captured to listen to music! In this instructables, which I am doing for the personal project (part of the IB program) and also for my personal interests, I will create a radio to see if we can make a quality stereo set!
There are two parts to the radio, one which is the circuit, and two which is the case and testing! For creating a box, sizes may vary, so my design might not be applicable to yours! Keep that in mind.
Please make sure to contact me if you require any help! I am not a specialist, but I have ran into multiple problems, most of which you could stumble upon as well!
Step 2: Collect All Materials Required
For this radio, we shall need various components. These can easily be bought in kits, but the specialty on the menu is the TDA7000, a Philips made radio reciever IC. These aren't easy to come by as the production is halted, but many different companies still have them in stock. As for me living in Germany, they are fairly common. Darius GmbH has a truckload of these specialties. The other parts required for the build are a variety of capacitors and audio components. The LM386 will be our audio amplifier so we can power a speaker in the set. Any variation of the LM386 is valid, for my build I have used the N-4 type.
List of parts (with links to where I had bought them):
Soldering station of any sort, rough sand paper, fine motor skills, patience, and time.
TDA7000, produced by Philips ()
LM386 N-4, bought through Conrad.de
Ceramic Disk Capacitors:
2x 10k resistor
1x 22k resistor
Other bits and bobs:
1x8 Ohm speaker
1x Antenne of any type, may just be a piece of wire!
1x 4-5 turns coil, (this will be explained)
1x Variable capacitor with the range of 10pf-20pf
1x Potentiometer 22k
9-12 volt power source (Fresh 9V battery reccomended)
1x Solderable circuit board (lochplatine it's called in german)
OPTIONAL BUT HIGHLY RECCOMENDED!
For testing purposes, a breadboard and jumper wires are highly reccomended. It is not required, but it would help out a lot!
Step 3: -- OPTIONAL, HIGHLY RECCOMENDED --
Before creating any circuit, I test it on a breadboard, as sometimes mistakes can happen when soldering straight away. Sometimes, small details might be missed when actually soldering. The circuit diagram comes from Bastelnmitelectronik, which I would like to thank, as although it is only in german, the website has a huge variety of information that I have learnt from.
Within the circuit diagram, it is easy to spot a general positive terminal and negative terminal, making the breadboard connections very easy (see diagram)! From my actual testing, you can see that I've taken a variable capactior from a kit, but I will refit this soon. With testing done, the radio sounds great with pristine audio, and can get very loud! Trying in different environments and configurations, I was able to capture a French channel from Germany, which proves it's effectiveness.
Adapted from Bastelnmitelectronik!
Step 4: Preparing the Coil
The coil is a gamble. It is recorded to require 4-5 turns, but it is really experimental. For me, I had to modify it multiple times to get it right. To create any coil, any thickness it acceptable. What must be done is take the wire, and wrap it around a cylindrical object 4 to 5 times, with extra lead over for when we will solder. Take a look at the picture, as I have used enamelled copper wire from an old transformer and wrapped it around a metal rod.
After coiling the wire, the ends must be sand paper'd so the connection points are well. Make sure to fully sand paper the ends, so that they can be cut to size when placed on the circuit board.
Step 5: Prepare the Variable Capacitor
Depending on what type of Variable capacitor you purchase / find, you will need to prepare it. Some have 3 connections, others 2, and I do not know what your type will require. Make sure to check online, or check this website that explains connections for even AM radios: http://www.petervis.com/electronics/tuning-capacit...
For mine, I only require to take it apart from it's generic holder. Others will have to connect leads that can be soldered later on. With any component, DO NOT SOLDER DIRECTLY. This can cause unwanted damage as heat passes through the components. When soldering, be swift and quick!
Step 6: Preparing the Chips for Soldering
When it comes to soldering chips, Don't solder it straight away! The chip will be ruined due to extreme temperatures. Instread, take an IC holder(see image), one that is 18 pin, and the other that is 8 pin for the audio amplifier. Solder these first, and place the chips after!
Step 7: Preparing Potentiometer, and Speaker
The speaker will almost always require 2 connections. Positive and negative. To make it easier, color code which is a positive connection, and which is negative. This will help in assembly to the case!
For the potentiometer, leads can be used so when assembling the case, it is easier to move around and orient in the way you want it. If you want to have a sturdy circuit with everything in place, you can solder it straight on to the solderable board. I have decided to go with leads, as it will make it easier for me when assembling.
Step 8: Soldering
DO NOT SOLDER DIRECTLY TO COMPONENTS. ONLY WHEN REQUIRED TO, BE SWIFT. HEAT CAN DAMAGE COMPONENTS!
With that said, here comes the fun part. Or the most painful, atleast. Make sure you are well rested and prepared with a soldering iron for some action. I would reccomend testing on a breadboard (step 2) to familiarize with the circuit, as it will help you greatly. To solder, one must push the leads of each component through the circuit board (in German: Lochrasterplatine), push the component through as much as possible, bend the leads and solder the component onto the circuit board. After that, take a wire cutter and cut off the extra metal from the component.
After one component, do the next, and next, and next, and next, aaaaand next, aaaaaaaaaaaand next, ........
Till you're done! To make the circuit connect, place solder between the components connections, and that will create a "path"!
This is tedious, but it's what you signed up for, right?
Step 9: Test & Troubleshoot
Hopefully you haven't run into any problems. I have, but with success afterwards. Here are a few details that might save your problem!
Too much interference?
Try squishing the coil. Sounds weird, but it will most likely be your coil acting so strangely.
Still too much interference?
Make sure you use a fresh antenna, it can be wire, but as i first used a solid rod antenna, I ran into problems like this, and I switched to a wire based one which worked even better.
I HEARD SOMETHING! BUT IT'S GONE!
The variable capacitor might have intereference from the outside. See if you can cover it with your hands, and if that works. For my variable capacitor it worked better enclosed than open in my room. With my box design in mind, that won't annoy me.
Step 10: Creating the Case and Presenting the Product!
This is where your creativity comes in play. If you desire a 3d printed case, go on ahead, and examine my model I've created in fusion, adjust to your needs (for your potentiometers, speakers, volume dials)! If you desire a wooden case, check the laser printing guide in the next step. The speaker will be a pain to place without laser cutting percisely.
Step 11: Additional: 3D to Laser Cutting
This won't apply to everyone, but for those who only have a laser cutter avalible (me), it is very effective to create a 3D model, and converting it to a printable format. I've used 123D make, a software that allows many different slicing techniques. It should be noted that the corners of the 3D model is curved,so slicing horizontally won't work. Slicing vertically down avoids this.
Step 12: Finishing Up...
That should be it! Place your components to the coressponding spaces, and the product is finished! Make sure to comment for help, I will try to respond as quickly as possible!