A FM Radio for one-dollar – How is this possible?
On the way out of the Walmart store – right where you check out - the place where smart merchandising people place items for those people who are impulse buyers and those who are unable to delay gratification – I saw a FM Radio for the price of one dollar. For the exchange of one dollar in United States fiat currency I could have in my possession a FM radio. Wow.
The radio runs on 2xAAA batteries, came with a earbuds, tunes the whole FM broadcast band, and has a light. Wow.
The radio runs on 2xAAA batteries, came with a headset, tunes the whole FM broadcast band, and has a light. Wow.
In a few moments, the prize was mine.
Can’t break old habits.
I have heard people tell stories of when they were a kid they liked to take things apart to see what was inside. If you are a kid, maybe 5-10 years old, then its fun taking things apart but unfortunately sometimes they did not go back together. Maybe your parents told you to stop doing this – taking things apart to see how they worked. But for many kids, myself included, one could not resist taking things apart to see what is inside and what makes it work.
At this point I have to mention a related story – you will find it in a past posting on this site. One of my friends, lets call her Elizabeth, has a son of about 10 years and a dog named Diamond. She told me that her son asked her what was inside Diamond. Now, that has got to be the place you draw the line on kids looking inside to see how they work. Although this kid may have a future in medicine lets save the dissection for high school, college, and medical school. Worst case scenario, Elizabeth comes home to find…
Doing the research
Before I opened up the radio I did a search on the Internet to find out about single-chip FM radios. I thought I was on to this radio before I looked inside to read the numbers off the chip
A good bet was the Philips Semiconductors’ digitally tuned TEA5767/68 FM stereo receiver IC
Philips Semiconductors’ digitally tuned TEA5767/68 FM stereo receiver IC is based on an innovative architecture concept that simplifies radio design, significantly reducing the number of external components. Delivering the highest performance levels, this one-chip radio solution occupies minimal PCB area (9×9 mm) making it ideal for all space-critical and low voltage applications such as mobile phones and MP3 players.
The single-chip TEA5767/68 is a miniature, digitally tuned radio IC that utilizes an entirely new radio architecture concept that replaces passive components and complex circuitry, with on-board silicon, drastically reducing the overall bill of materials and making design-in easier. It requires zero external alignments, resulting in shorter design times and lower manufacturing costs due to simplified component placement and reduced logistics overhead. Also, being adjustment free, it delivers increased quality and reliability, both in manufacture and throughout its lifetime in your end application.
If this was it, it looks like I had quite a chip on my hands. This chip interfaces with a microcontroller over a 3-wire bus or a I2C-bus.
Doing more digging I found a application note on the TEA5767/68. This was more information than I ever wanted to know – but very interesting. Turns out that the manufacturer provides a demo board so developers can play with this thing along with software that runs on a PC to communicate with the chip.
Some of the things that the microcontroller can tell the TEA5767/68 single chip FM radio is Mute left/right, search up/down, mono/stereo, set band limits, and set Deemphasis. The Microcontroller can ask the TEA5767/68 status of the tuning, if the band limit is reached during scan, and query a number of settings.
Talk to me – this is what you can say to the TEA5767/68 over the communications bus
You can find details on all this in the application note in the Resources section of this posting.
What’s inside Diamond?
The appointed time arrived and I decided to deploy the plasma cutting torches and the surgical instruments. I scored two one-dollar radios – one to use and one to explore. The survival of the victim was not of concern to me.
Below is a series of images showing the disassembly
Out of the case
The buttoms are Power, Light, Scan, and Reset
When I got inside the radio it was not what I expected. I didn’t find the TEA5767/68. Instead I found an SC1088. Checking the internet, this is what I got
The SC1088 is a bipolar integrated circuit for use in mono portable and pocket radios. It is used when a minimum of peripheral components (of small dimensions and low costs) is important. The circuit contains a frequencylocked loop(FLL) system with an intermediate frequency (IF) of about 70kHz. Selectivity is achieved by active RC filters. Detuning related to the IF and too weak input signal is suppressed by the mute circuit.
Equipped with all stages of a mono receiver from antenna to audio output.
* Mute Circuit
* Search tuning with a single varicap diode
* Mechanical tuning with integrating AFC
* AM application supported
* Power supply polarity protection
* Power supply voltage down to 1.8V
Here is the block diagram for the SC1088
This is most likely close to a schematic that represents this radio. It some from the datasheet for the SC1088 which you can find in the Resources section of this posting
Give me the China Price
Certainly the TEA5767/68 is for high end applications like mp3 players that have the built in FM radios. If you want the China price then you get the SC1088. From the diagrams you can see that the SC1088 can be set into search mode with a push of a button – no data bus, no microcontroller. The SC1088 is also capable of receiving AM. See the datasheet in the resources section to see its capabilities and application schematics.
I looked for pricing on these chips but it was not available without subitting an inquiry to a supplier.
While doing more research on this I found a few more web sites created by people who like to take things apart. On one of these sites the writer says he bought his single chip radio at Dollar Tree. He says he paid two dollars. That guy got ripped off – I paid one dollar
In 2009 the national conversation is about manufacturing going overseas. How much does it really cost to manufacture a FM radio, package it, get it over to the United States, put it into a distribution center, get it into the stores, and price it for one dollar? Can a retailer like Walmart price this at one dollar and still make a profit?
TEA5767/68 Application Note (highly recommended reading)
Other people wanting to know what’s inside Diamond
What will they think of next – how low can you go?