Hi everybody! I'm fairly new to Arduino, and a couple of months ago at Maker Faire I saw a Nixie tube clock and was completely entranced by it. An idea that I have for a project is to use my Arduino to measure the frequency and volume of a disassembled clock radio and then display the station and volume using Nixies and LED's.
My plan is to use a ArduiNIX shield with my Arduino Mega 2560 (plenty of pins!). But my question was: is it possible to measure a radio's frequency with the Arduino? Volume, I know shouldn't be a problem to measure, but I could not find anything about an Arduino reading a variable capacitor. Is this a sensible project to try and undertake? If not, I can just make a nice clock.
You will need to ask yourself, what frequency are you reading. No where in your radio will you find the receive frequency. You may find a local oscillator frequency but that will be high or low by the IF frequency. That's assuming you even have access to a point were you could measure that.
Look at the datasheet for a TEA5767. This is a small integrated FM receiver that is easily controlled by a processor. This might meet your need for radio. You would need to add an audio amp. One that is easily controlled by an Arduino does not come to mind.
You might also look at a RDA5807 module. They have a bit higher audio output such that they can drive a small speaker without an amp but you would not have a volume control. You can get a RDA5807 module off ebay for under $10.
The probable is that the Station Frequency is not easy to measure.
Although there have been changes over the years. Almost all receivers use some form of heterodyne receiver design.
The heart of the heterodyne receiver is the "mixer". It takes your station signal and mixes it with a local oscillator. The signals are subtracted one from the other and the difference is then processed. That difference frequency is called the IF or intermediate frequency. The IF does not change. The change the receive frequency you change the frequency of your local oscillator. The difference (IF) does not change.
You might be able to measure the IF, but that doesn't change. You might be able to measure the local oscillator but that is different from the receive frequency by the frequency of the IF. But you can not measure the receive frequency.
This is all assuming you have access to these signals. Today's receivers often have local oscillators built onto the same chip as the mixer and IF chain. So you may have your Antenna going in one pin and audio coming out another and not way to sample anything in between.
That is why it is suggested that you use a receiver chip that can be processor controlled. You set the frequency of the chip to 95.5 and then display 95.5. The chips I mentioned in reply #2 have the feature of scanning for a station and then when they stop you can read from a register what the frequency is. They are cheap and simple. I am cheap. It is part of the challenge, any problem can be solved by throwing money at it. It is more of a challenge to do it on a budget. For example, for your clock, you could spend several dollars for a high accuracy time module, or you could soldier a crystal to pins 9 and 10 of an Atmega328 and have a clock. An Atmega328 is the same processor as in most Arduinos and is much cheaper than an Arduino and you can use the full IDE and all the libraries to develop your clock.
@zachmart,
Maybe you are after something more like this
"Description: This is an evaluation board for the Silicon Laboratories Si4703 FM tuner chip. Beyond being a simple FM radio, the Si4703 is also capable of detecting and processing both Radio Data Service (RDS) and Radio Broadcast Data Service (RBDS) information. The Si4703 even does a very good job of filtering and carrier detection. It also enables data such as the station ID and song name to be displayed to the user.
Using this board we are able to pick up multiple stations just as well as with a standard FM radio. The board breaks out all major pins and makes it easy to incorporate this great chip into your next radio project. Also, by plugging headphones into the 3.5mm audio jack, you effectively use the cable in your headphones as an antenna! Therefore, this board does not require an external antenna if using headphones or a 3.5mm audio cable longer than 3 feet."
The heart of the heterodyne receiver is the "mixer".
FM radios generally use phase locked loops.
I don't understand your point. Do you feel that the "mixer" is NOT the heart of a heterodyne receiver or that you feel the local oscillator is more important.
Thank you so much everyone for your help! I think I'll take RandallR's suggestion and use the TEA5767 with a simple LM386 Amp. This should be pretty easy to integrate with the Nixie tube display. Thanks again!
zachmart:
Thank you so much everyone for your help! I think I'll take RandallR's suggestion and use the TEA5767 with a simple LM386 Amp. This should be pretty easy to integrate with the Nixie tube display. Thanks again!
Let us know how the project goes. The TEA5767 is a cheap way to go (under $3). Soldier is the part that gave me the most problems. I put together a little library that I found useful if you need it.
Hi all!
This sounds like an interesting project!
I am building a headphone amp and it would be so cool to display the volume position with 2 nixies!
The problem is that I'm totally lost when it comes to programming... I know it shouldn't be too difficult, I found a perfect 2-digit nixie driver at www.ogilumen.com and I just need to figure out the Arduino code that will translate a potentiometer value to the correct driver input signal. Help, anyone?
