Hi i'm Erik an electronic engineer and Hobbyist :)
In this instructable i'll show you how to make a fully functional AM Radio using only 3 transistors and some recycled components!
Step 1: Parts List
We'll need some electronic components and any other thinks that you like to add for modify the radio
3- NPN TRANSISTORS (I RECOMMEND YOU TO USE GERMANIUM TRANSISTORS AC187) OR 2N2222 ANY GENERAL PURPOSE TRANSISTOR.
1- VARIABLE CAPACITOR FROM AN OLD RADIO O FROM RADIOSHACK STORE
1- FERRITE COIL (ANTENNA AM RADIO) FROM AN OLD RADIO TOO.
1- 0.01 uF ceramic capacitor (103).
2- 0.1 uF ceramic capacitor (104).
1- 2K2 Resistor.
1- 1K8 Resistor.
1- 3k3 Resistor (if whistles appears in the output cound you can to change the value between 2K7 TO 3K3 ohms).
1- 100k Resistor.
1- 10 Ohms Resistor.
1- 0.1 uF electrolitic capacitor.
1- Little Speaker (you can to choose add plug for earphones).
1- 1.5 V Battery (AA/AAA/C/D) anyone you have.
1- 1.5 v bulb (optional).
1- ON/OFF Switch
1- Battery holder
1- soldering iron
1- some solder
1- cable for electronic circuits
1- Wood enclosure or anyone you have it's for to protect the proyect and have better look.
1- dill or anything to make the holes in the enclosure.
1- PCB board of cooper for to make the circuit.
1-Some Glue like silicon pistol.
1- Earphone female connector (Optional).
Step 2: Schematic and Description
The schematic is simple:
The ferrite coil from am radio and a variable tunning capacitor sintonize the frecuency and the other circuits is amplification and selectivity.
Q1 y Q2 are a cascade darlington transistor array for amplify the current.
R4 delimit current and the frecuency of sintonizacion for to polarize the transistor Q2
C1 & R5 is a configuration for make the sintonization between teh ferrite coil and the variable capacitor.
C3 is a filter electrolitic capacitor
Q3 works as a driver of the speaker for amplify in a retroalimetation configuration.
R2, R3 Y C5 polarize the transistor and give him more gain.
Speaker may be any little speaker but with high impedance more tha 4ohms for better results but you can to use anyone you want :)
If you have other type or other model of air capacitor you can try diferents tipes of conection or to searh the diagram in google, remember you can probe if the circuit is working if you connect a earphone between collector of transistor Q2 and POSITIVE (+) of the battery.
-If you have some problems listening the frecuency or the station are so difficult to hear you can CHANGE THE R4 RESISTOR FROM 2K7 TO 3K3 if whistles appears.
-Remember to use a good ferrite Am radio coil, use the images of the top for to guide you, if you decide to construct the coil please make it for Am Radio especially designed.
-Transistor may be 2N2222, 2N2904 OR ANY OTHER GENERAL PURPOSE NPN TRANSISTOR, BUT I RECOMMEND YOU TO USE GERMANIUM TRANSISTOR AC187 for better results, because the radio only works with 1.5 Volts battery and the germanium transistor has a B-E union rupture voltaje of 0.3 v and the normal transistor of silicium the B-E union is 0.7 v.
Step 3: Prototipe in Protoboard
It's very important before to make in a PCB Board the circuit to probe it, and what does better than a protoboard? :)
Lets try, check all the connections before to connect the battery, then solder the pinout of the coil and the variable capacitor.
PD: I added a little video of the Am radio circuit function!
Step 4: Making the Circuit and Testing...
The PCB Making is not showed but whatever i add the pcb final circuit and the schematic in PDF.
Note: is the version 2.0 of the PCB: Make some changes than the original and it's smaller :)
A little show of the images and the circuit construction.
Mounting the speaker and glue it to the wood box, i drilled some hole for tho the sound, it's not the best but are useful :D
Take a look of the final PCB board with the components soldered.
Mounting the PCB Antenna ferrite coil and variable capactiro in the box, too i add a ilttle 1.5v bulb light (not led) powered by a single 1.5V Battery.
Final mount of the box with the battery holder and a on/off switch as a complement.
Step 5: Finalized 1.5V AM RADIO
Ok i made it in a single day, i hope all the people are visiting my instructable make one, the radio is the best hobbys of the word, yo can try different types or modifications of my radio
-You can supply with a lemon battery
-Solar call powered
-Wind powered etc.
-Please suscribe to my channel in youtube and in instructables for more interesting and funny easy projects to make :)