On the Bench
On the bench with Bill Chappell
Installment # 1 part 1 : Building an Ghost Box Radio
Funny it’s been over two years ago when I pulled the Mute pin from a inexpensive radio and started the hack craze! Today that hack has found its way into 100’s of websites, Books and even a couple TV shows. So, why a ghost box? Hey why not? They produce some interesting results and people enjoy using them.
Ground Rules :
1. If you don’t own a soldering Iron this is definitely not for you!
2. This is How I’m doing it, the whole Idea here is to get people working on new ideas
3. This is an example how to, Not a product. Build and Operate at your own risk
4. Digital Dowsing LLC and Bill Chappell are not responsible for errors or omissions
5. You MAY NOT reproduce any of this On the Bench series including schematics, layouts and software. Please add a Link to this site from your own pages. All schematics, Code, Layouts
and images are copyrighted .
To build this project you need a firm understanding of electronics and programming.
My whole idea is to inspire new people to go out and do it for themselves. America needs
more active inventors and engineers.
Since this is going to be a three part series please don’t email asking for sound bits or source code.
I’ll post them in parts 2 and 3.
So, here’s then device I’m building … a 3v FM scanning Ghost Box that can fit in the palm of your hand!
I’ll be using an inexpensive FM radio module from SparkFun.com cost is 15.00
part # WRL-08972
They have the data sheets and example for this device on their site.
This module has all the tedious items done, we don’t have to wind coils, or set tuning slugs
Nope, were jumping right into the 21st century and using new technology.
I’ll be using a PIC 18F26K20 low power microprocessor and a LM4861 amplifier chip.
The PCB “Printed Circuit Board” will be a hybrid of both thru hole and surface mount to
Take advantage of lower cost, easy to find common parts such as the FM module and the switches.
When complete the radio should be able to scan up and down, adjust scan rate and perform
random tuning functions. The circuit I have laid out calls for 4 leds to display mode, volume and direction of scan. Here’s the preliminary PCB and schematic.
The circuit board in real life it’s only 2.25 x 1.25 truly fits in the palm of your hand.
By designing at 3 volts, battery power we don’t need voltage regulators and were able to use parts that have drop out voltages of less than 2.5 volts . By adding a microcontroller were able to make the radio work almost any way we want.
What makes this so appealing is the low cost, simple design and the ability to control the FM radio with a standard IC2 interface or an SPI if you wish. In the Next segment I’ll post a complete BOM,Schematic and talk about the firmware to run the PIC. In the last segment I’ll post a video of the completed project including the firmware hex file. So if you’re really a techie, dust of your soldering Iron.
Please, don’t start buying parts … If you’re not familiar with all the aspects of building a device like this.
Lets Have fun Out There.
-Bill
What’s the Next device to be ON THE BENCH, Starting in March I’ll build a simple low cost
strobe for IR and UV.