HackerBox 0066: Radio Star

Greetings to HackerBox Hackers around the world.

We're making radio waves with HackerBox 0066. Assemble a TEA5767 single chip FM radio receiver featuring an 8051-based microcontroller for digital tuning. Explore three different radio modes and integrated OLED graphics using the LoRa 32 module from Heltec. Study and experiment with hardware and code to implement Wi-Fi, Bluetooth, and Long Range wireless radio communications. Construct a custom 915MHz, quarter-wave, ground-plane antenna. Hack the Planet.

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Supplies

This Instructable contains information for getting started with HackerBox 0066. The full box contents are listed on the product page for HackerBox 0066 where the box is also available for purchase while supplies last. If you would like to automatically receive a HackerBox like this right in your mailbox each month with a $15 discount, you can subscribe at HackerBoxes.com and join the revolution!

A soldering iron, solder, and basic soldering tools are generally needed to work on the monthly HackerBox. A computer for running software tools is also required. Have a look at the HackerBox Deluxe Starter Workshop for a set of basic tools and a wide array of introductory activities and experiments.

Most importantly, you will need a sense of adventure, hacker spirit, patience, and curiosity. Building and experimenting with electronics, while very rewarding, can be tricky, challenging, and even frustrating at times. The goal is progress, not perfection. When you persist and enjoy the adventure, a great deal of satisfaction can be derived from this hobby. Take each step slowly, mind the details, and don't be afraid to ask for help.

Step 1: FM Radio Receiver Kit

The radio kit implements an FM receiver featuring microcontroller-based digital tuning.

Featured elements include:

• TEA5767 Single Chip FM Radio (datasheet)
• STC89C52 Microcontroller (datasheet)
• LM386 Audio Amplifier (instructable)

FM Radio Receiver Schematic: See attached PDF File

Step 2: FM Radio Receiver Assembly - Phase 1

Start by soldering the castellated edges of the ten pin TEA5767 module (how to video). Be sure to match the orientation of the module illustrated on the PCB silkscreen.

Next, solder the thirteen axial resistors. These are blue with colored stripes. The value of each resistor can be determined from the colors of the stripes, but it is always best to double check by measuring the resistance with a meter. The resistors are not polarized, so they can be inserted in either direction, but they are not interchangeable. The value of each resistor must match the value specified on the PCB silkscreen.

• ELEVEN 10K (brown, black, black, red)
• ONE 4.7R (yellow, violet, black, silver)
• ONE 220K (red, red, black, orange)

Complete Phase 1 by soldering FIVE Ceramic Capacitors. These can also be inserted in either direction.

• THREE "104" Capacitors (100,000 pF = 100 nF = 0.1 uF)
• TWO "20" Capacitors (silkscreen shows 22pF, but 20pF is close enough)

Step 3: FM Radio Receiver Assembly - Phase 2

FOUR Transistors Q1-Q4

These are all the same value. Note that the shape on the silkscreen matches the shape of the package (flat on one face and round on the other). Match these up.

Crystal Y1

Can be inserted either way.

LED D13

Diodes are polarized. Note that one of the PCB holes has a "+" marking on the silkscreen. The longer pin goes into that hole.

50K Wheel Potentiometer

The volume adjustment dial only fits onto the PCB one way. Apply some extra solder to make sure that the two tabs at the edge of the PCB bond to the corresponding pads to provide extra mounting strength. The five pins make the electrical connection, so we sure they are properly soldered as well.

FIVE Electrolytic Capacitors

These are polarized and must be inserted in the correct orientation. The capacitors have a white stripe marking "-" while the "+" terminal has a longer pin. Insert the longer pin into the hole marked "+" on the PCB silkscreen. There are THREE 100uF (larger) black capacitors and TWO 10uF (smaller) black capacitors. The three larger circles on the silkscreen (C3, C9, C11) are for the 100uF caps and the two smaller circles (C7, C8) are for the 10uF caps. Leave enough slack in the leads for C7 so that it can be bent to lay down flat against the PCB. This is required so that the U1 microcontroller can be inserted into the socket over the capacitor.

Step 4: FM Radio Receiver Assembly - Phase 3

Power Button and TWO Tuning Buttons

These can be mounted either way around.

Barrel Socket for 5V Power

This only fits one way. Later, the power input can be supplied using the included USB-style power cable.

TWO DIP Sockets

Align the half-circle marking on the PCB silkscreen with the similarly shaped notch in each socket before soldering the socket pins to the PCB. Solder the sockets without the chips inserted to protect the chips from thermal damage.

Four-Digit Eight-Segment LED Display

Orient the display module such that the decimal points are closest to the large MCU chip. It will not work if it is inverted.

Insert TWO DIP Chips

Be careful to align the half circle notches on one end of each chip to the PCB marking. Be even more careful to not to bend any of the chip pins during insertion.

Solder Antenna onto PCB

This will take some extra heat and solder. Take your time.

Red and Black Speaker Wires

On the PCB, solder the black wire into the hole closest to the volume dial and the red wire into the other hole (the "top" hole). On the speaker, solder the red wire onto the "+" terminal and the black wire onto the "-" terminal.

Step 5: LoRa 32 Module - Radio Triple Play

The very cool LoRa 32 module features an ESP32 dual-core processor, an integrated OLED display, and three radio interfaces:

1. Wi-Fi

The LoRa 32 module provides IEEE standard 802.11 b/g/n Wi-Fi operating on 2.4GHz native to the Espressif ESP32 SoC.

2. Bluetooth

The LoRa 32 module supports the latest BLE Bluetooth 4.2 as well as classic Bluetooth. This allows communications to be established with both old and new Bluetooth phones, tablets, and other smart devices.

3. LoRa

The LoRa 32 module incorporates the SX1276 LoRa Core Radio Transceiver (datasheet) and features a tiny I-PEX (aka U.FL) coax connection for LoRa radio comms. Be sure to have an antenna attached to the LoRa coaxial RF connection before firing up the LoRa radio. Failing to do so could permanently damage the SX1276 LoRa transceiver circuitry.

Module Schematic: See attached PDF File

Step 6: LoRa 32 Module - Arduino IDE

1. Be sure the antenna (not just the cable) is connected to the I-PEX antenna port
2. Connect the LoRa Module to a PC using a microUSB data cable (not a charge cable)
3. The HELTEC logo followed by a Wi-Fi demo should appear on the OLED display
4. Install the Arduino IDE and ESP32 Board Manager as outlined on this page
5. In the IDE go to Tools > Manage Libraries...
6. In the pop-up search for "HELTEC ESP32 Dev-Boards" and hit INSTALL
7. Exit back to the IDE main menu
8. Select: Tools > Board > ESP32 Arduino > Heltec WiFi Lora 32(V2)
9. Select the correct port for the connected module
10. Open File > Examples > Basics > Blink
11. Compile and Upload to the module - the white LED should now blink
12. Open File > Examples > Heltec ELTEC ESP32 Dev-Boards > Factory_Test > WiFi_LoRa_32FactoryTest
13. Compile and Upload to the module - this should replace the original demo with OLED output

Step 7: LoRa 32 - WiFi Radio

Download the attached sketch HB66_WiFi_Demo.ino and program it onto the LoRa 32 module.

The sketch will display the Wi-Fi Logo on OLED. Then it will expose an open Wi-Fi Access Point named ESP32-Access-Point (AP). Attach your PC (or a phone/tablet) to that AP. The OLED will Display an IP address. On the same PC (or a phone/tablet), point any browser to that IP address. A tiny webserver implemented by the sketch will publish an HTTP page showing a button that can be used to toggle the white LED of the LoRa 32 module.

To experiment with using the LoRa 32 as a Wi-Fi Station (instead of a Wi-Fi Access Point), watch this example video.

Step 8: LoRa 32 - Bluetooth Radio

This video and associated project page from Random Nerd Tutorials demonstrates the use of Bluetooth and Bluetooth Low Energy (BLE) communications on the ESP32.

Step 9: LoRa 32 - LoRa Radio

LoRa (Long Range) Wireless is a low-power wide-area network modulation technology. LoRa is based on spread spectrum modulation techniques derived from chirp spread spectrum (CSS) technology. LoRa uses license-free sub-gigahertz radio frequency bands like 433 MHz, 868 MHz (Europe), 915 MHz (Australia and North America), 865 MHz to 867 MHz (India) and 923 MHz (Asia). LoRa enables long-range transmissions with low power consumption. The technology covers the physical layer, while other technologies and protocols such as LoRaWAN (Long Range Wide Area Network) cover the higher network layers. It can achieve data rates between 0.3 kbit/s and 27 kbit/s depending upon the spreading factor. LoRa devices have geolocation capabilities used for trilaterating positions of devices via timestamps from gateways. (Wikipedia)

If you already have a LoRa gateway or are near one (check The Things Network) you can connect using the LoRa 32 module. In not, you can use the LoRa 32 module to set up a gateway of your own.

A number of interesting projects have been implemented using LoRa technology:

Meshtastic

Doomsday Communicator

Ripple Messenger

TinyGS Open Source Global Satellite Network

Disaster Radio

Wyld LoRa Sats

Step 10: Quarter-Wave Ground-Plane Antenna

A ground-plane antenna can be constructed to operate at around 915MHz.

• Initially, cut FIVE 90mm lengths of 20 gauge copper wire
• Solder one to the SMA center conductor (this will be the radiating element)
• Solder the other four to the corner holes of the SMA mounting flange
• Straighten all five wires (repeatedly) until they extend out symmetrically
• Trim the Radiator to exactly 78mm measured from the flange
• Trim the FOUR Radials to exactly 87mm measured from the base of the Radiator
• Bend the Radial elements down 42 degrees (around 40-45 should be fine)

Antenna tuned to different frequencies can be similarly specified. Use the online calculator for quarter-wave ground-plane antenna geometries to calculate the necessary element lengths.

Note that the length of each Radial is approximately 1.1 times the length of the Radiator.

To create a mount for the antenna, place the threaded SMA connector of the IPEX-to-SMA coax through a non-conducting structure. A great option is a length of PVC pipe with a flat cap (often called a "test cap") on the end. A hole for the coax cable's SMA connector can be made in the cap, and then after the threaded connector is secured into the hole, the other end of the PVC can be secured (for example using a hose clamp or burying into the ground). Then the ground-plane antenna can be threaded onto the exposed end of the coax cable's connector.

Step 11: We Can't Rewind, We've Gone Too Far...

We hope you are enjoying this month's HackerBox adventure into electronics, computer technology, and hacker culture. Reach out and share your success in the comments below or other social media. Also, remember that you can email [e-mail] anytime if you have a question or need some help.

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