Category Archives: Moushira Elamrawy

Live Radio –Phew!

OK, so I have been developing the work around the live radio over the last month. When I say last “month”, you assume that I am now done with three radio projects instead of one, but unfortunately, that’s not quite the case. My main interest in this project is to create a complete system composed of sound transmitters and receivers that are mobile and work efficiently together.

I have been following the checklist I set for myself on the last post, which starts by shrinking the circuit. Before I start, I should tell you that I did a lot of miles in this project. Distance miles. Went to the airport twice to pick up my DHL shipments, where in theory I paid for a door to door delivery, then ended up skateboarding between airport terminals. :)

Back to shrinking the circuit, I ordered AtTiney84 from Farnell (and picked it up from UPS office in Hospitalet!). The pieces are really tiny as you see on the left of the right picture, but they don’t support all arduino functions, which is what I discovered after getting them. Of course! So my other alternative was to use the Atmega328P, which is the same chip of the arduino.

uploading sketch to standalone chip

Board and shield I don’t have enough expertise in any of these details, but the web is a blessing. Check MIT references here and and arduio pages. So, I burnt the bootloader for the new chips using 2 arduinos, then wired the chip on a breadboard and uploaded sketches using arduino as ISP. Those are very interesting and cheap methods (since we don’t use and external programmer) for programming the chips. Then I tested the transmission pieces with the receiver pieces and they work together perfectly. For a newbie, that was a lot of learning and loots of troubleshooting! But awesome, now I can save size and money (the chip is 2.5 EUR while an arduino is 25 EUR! –big difference) and run the piece independently using 2 (3V) batteries. So that operation is done and tested, I needed to complete soldering the standalone board with the FM shield, and pack this is a nice 3D printed casing.

Quick render of the case

The printing thing took me over a couple of days of troubleshoot, and logistic problems, and other random stuff, so for the final presentation, realistically, I don’t think I will be able to finish those pieces (still need to solder the boards as well!), but I made a quick up mock up using polypropene, to give an idea of how this should look like notice the parabola at the microphone outlet, I would like to test this idea in the future using different geometries and materials.

Unfinished 3d prints

So for the demo, I guess, I will build a unit for the receiver, and keep the transmission units arduino dependent, just to illustrate the idea. I would have loved to finish everything . . . but time is fast. :)

Reception unit

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Personalized Live Radio

The idea of this project is to simply create audio capturing unites, that transfer sound over FM. Using multiple transmitters, we create a receiver device that acts as an output for different audio channels, and which also has a mixer. I would love to add recording functionality as well, if I managed to. Below is a diagram illustrating the simple system architecture:

My initial thought was to capture and manipulate live outdoor sounds (tree leaves, car wheels, ..etch) however due to sound quality and signal transfer of FM available ranges with this shield (50 ~70 m). I am now testing with capturing unpredictable sounds, from very close objects.

Below are images from testing the transmission from a tree as well as testing for different sound reflection techniques:

Right now, I need to:

1. Find a better way to design a compact transmission unit that is small, independent, with good powering solution (one option is to use Arduino Fio and Lituhum battery , another even more compact option is to use ATtiny85 chip

2. Define interesting sounds for personalized channels

3. Make sure the analog mixer will actually work nicely with these generated sounds (I really want to rely on a variable resistance technique to change sound, without using any interface)

4. Amplification, if needed..

If all the above went well, I should be able to finalize it and build the radio :) — you just need to wish me good luck!

Happy Holidays :)

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The dear drawing machine is almost there..

So now the dear drawing machine is alive, watch her in action below. The darker the light the higher the resistance and thus the faster the speed of the motor. This machine is designed to be hanged on the wall to react to people passing by. If you passed by, or stand in front of it, it will start to draw according to the level of shade you project.

This is a very simple application of using a variable resistance (in this case a photoresistor (LDR)) to change voltage via PWM. Main circuit components are an Arduino UNO, LDR a 10K ohm resistor, a transistor, and a motor, and thats it. . The variable resistance is read using AnalogRead, its value is fed into the transistor base pin via PWM pins using analogWrite, and thats it for the voltage to change according to light making a difference in motor speed. Several manipulation could be done afterwards, starting from assigning different values of light resistance sensitivity to each motor, all the way to making smart moves by designing code conditions according to serial read values from serial port. As you see, the design is simple but building the machine has some mechanical challenges starting from motor alignment to adjusting all the pieces together. I had a very successful first demo (ask Alex and the group –they witnessed :) ) now I am providing better motor support and eliminating wiring connections, after that I should work on improving the code for smarter reactions.

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The dear drawing machine

So I got an obsession with this kind of machines which come in different shapes and designs. I initially planned to build a very simple analog circuit powered by a pair of AA rechargable batteries connected to SunMod solar strip, along with a resistor, an LDR, and an LP2950 voltage regulator. The idea was to change resistance with light, so when you stand infornt of the machine and block the light it starts to draw. Then Alex advised that I use Arduino for better resistance control, so I said OK :) The idea is the same but the components are slightly different, so is the protocol.
In this case, we will get the value from photoresistor using AnalogRead and feed this into the transistor’s base pin via PWM and thus change speed of motor with resistance. It is working now, however, the sensitivity of the LDR doesn’t seem to correspond nicely with the motor spin, I increased the base resistor, but more tweaking is needed and vamos a ver ! :)
//more to follow

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