ook demodulation update

Another small update

The signal has been simplified for now, until I know what is going on. There will be two LEDs for now. These will be turned on and off using OOK modulation. There will be three parts to the signal. The demodulator will use the following sequence;

• The starter bits are 1 1 0
• A bit of 1 or 0 to select LED 1 or LED 2 respectively 
• A bit of 1 or 0 to turn the LED on or off respectively 

The 'starter bits' are longer than any passable following sequence to help prevent errors.

Here is an example of two cases blue LED 1, on and red LED  2 on.

 

I haven't applied the leds yet it's just an idea. I first need to demodulate the signal and remove the nose.

To remove the nose I plan on using a exponential smoothing filter, this is by a recommendation of some stranger I ment at swing dancing.

OOK modulation daily update

Currently I'm brainstorming methods of initiating the communication. The most likely method I will use is a long pulse followed by a shorter time were nothing will be transmitted. Where the summed time of both the pulse and the blank space will be longer and different than any possible next communication.

This idea will be developed further in the next posts. The following figure came from the previous mentioned idea. A pulse of 1000 milliseconds and a break of 500 milliseconds, this is followed by periodic ones and zeros.



My idea is the pulse and blank then triggers the data sequence of the periodic ones and zeros in this case.

slow progression -- PAK - ook the modulator

The cheap microphone/demodulator I'm using was purchased from China for next to nothing and I got what I paid for. I can barely tell the difference between the signal in the background noise. You will see in the figures my signal-to-noise ratio is somewhere between three and four. This is with the low powered buzzer just inches from the microphone.

The cheap microphone will work for now, I bypassed the digital output from a comparator. Instead I am using the analog signal. yesterday's post was while I was still attempting to use the digital output.

Here are a couple references with the analog output from the microphone, in figure 1 I clapped three times, figure 2 there are several short pulses from a buzzer followed by a break ending with a long buzz, figure 3 I messed with the wiring a little bit and I think there may have been some improvement using the same procedure used in figure 2, however it may just be less noisy.

figure 1: clapping



figure 2: buzzer from 2 inches away


figure 3, rewired.

Before purchasing some transducers I want to get an idea of the noise environment I will be testing the system in. For now I will work with these cheap Chinese sensors to develop the software while I consider a more permanent transducer.

One of those days

Today was one of those days that everything goes wrong and everything breaks... including my car.... There was some small progress with the ROV.

The wireless communication is started. I am stepping away from the 8-PSK for a small time and using a for of ASK that is OOK modulation. It looks like a good start.



on the left is my rudimentary modulator and on the right is also a rudimentary demodulator. It almost didn't work and has a LOT of work to be done.

Sofar the demodulator lights up an LED when it hears a tone, it will be some time before it can send and receive live video.

School break goal 1 LTspice

There is a quick update to keep myself honest to my goals for winter break. Here is part of the first step, LT spice for the ROV. The UDOO development board in LTspice.

I'm back for the break

I've been M.O.A. this last semester I have been working on my senior design project with FSAE - formula society of automotive engineering designing a race car. This has taken up time I would have otherwise spent on the ROV.

I have gained some experience with FSAE that I am going to apply to the submarine. Most notable, logging information better. 

For winter break there are three primary goals:

1. Map the wiring for the UDOO development board on LTspice.
2. Re-add the ability to do send and test for the vertical access (be able to go up and down)
3. wirelessly communicate to the ROP using PAM holds amplitude modulation.