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Sound effects from robots

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By Samira TJBA

February 5, 2010

Hi, i am part of a team building a robot which can trakc and fight another. The robot we are supposed to detect is supplied fitted with a 365 degree high intensity side emitting red LED modulated at 2048Hz.

our team is thinking of a twin t filter for the job, but we would like some advice on this.

Also, we want our robot to produce noises. How can we do that? We want to record ourselves.

 

Thanks.

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By Samira TJBA
@ Wed, 2010-02-10 19:00
We dont really have an option about the L298 :( We are supposed to be working with that and we have already designed our motor drive PCB, just hoping to find a solution to the voltage drop.
By TeleFox
@ Thu, 2010-02-11 00:13
TeleFox's picture

The voltage drop is a function of the properties of the L298 and the current draw by the motors, so if you can't change either it's not going to go away. You could get a higher voltage supply, but it will either be physically larger, or not run your robot for as long off a single charge. Also the more voltage you feed the motors, the higher the motor current, and therefore the voltage drop across the L298 will probably go up a bit too... but at least you'll get more speed and power from the motors.

The other option, using a voltage booster, has a few potential drawbacks too. I don't know what kind of current your motors are drawing, but to get a voltage booster that can handle such a current would probably cost a bit, or take some serious design work to build. In the end I suspect that it wouldn't be worth the hassle to add one of these, especially since the booster won't be perfect, and will further decrease battery life.

By Samira TJBA
@ Wed, 2010-02-10 00:05
Also, we are using an L298 Dual H-bridge to drive the robot motors. We are using 12 V DC batteries, but we get a drop of 3 V across our L298. We are really keen on boosting the voltage so that our motors can run faster. I have looked into power boosting circuits and they look very complicated. Any suggestions in this area?
By TeleFox
@ Wed, 2010-02-10 00:25
TeleFox's picture

Rather than boosting the voltage, I'd suggest looking into a better motor driver, preferably one that uses relays or MOSFETs to reduce the voltage losses. There are several interesting motor driver designs here on LMR (search bar is your friend), and many many more out there on the web.

You can get motor driver ICs that are similar to the L298 but with better voltage drop characteristics if you have a look around.

By Samira TJBA
@ Tue, 2010-02-09 23:19
We are using C. Thanks for your info, I am looking into it! :)
By Samira TJBA
@ Mon, 2010-02-08 21:59

Thanks for the Phillips version, it was much better,

 

I am using a   Freescale HCS08 microcontroller. Can anyone please tell me how to start on recording noises which our robot can generate using a speakerphone when performing specific tasks? What is the best way to integrate all the circuitry needed?

By TeleFox
@ Tue, 2010-02-09 00:26
TeleFox's picture

How experienced are you with programming the HCS08? What language are you using?

You can add a tiny electret microphone to your robot, or a 3.5mm microphone jack, and use the HCS08 itself to record the sound data into memory when a button is pressed (or whatever, depending on available input options). Piezo speaker elements aren't so great at reproducing lower frequency sounds, so make sure you use a proper coil speaker (a small mylar diaphragm one should do nicely). Speaker driver circuits for microcontrollers are typically very simple, so I won't go into that for now.

If you're not so hot on the programming side, you can get an external IC to do almost all of the work for you. The ISD1212 is one such chip that I've used myself, but there are many others out there. They usually give you a recommended circuit as well, which is handy. The IC is able to do all the recording, storing and output by itself, and you can either use buttons or the microcontroller to send signals to it. You may want to have a manual record function, but the microcontroller determins what sounds are played back and when. Since the IC is doing all the hard work, the micro doesn't have to dedicate memory and time to processing the audio.

By Samira TJBA
@ Sat, 2010-02-06 19:26
if you could breakdown the working of the PLL, i,e, from how it would detect the signal to how it would output it, it would be really helpful, thank you.
By OddBot
@ Sat, 2010-02-06 22:41
OddBot's picture

I posted a link to the datasheet. Here is the Phillips version which explains it better.  Note: the VCO is not required for your project, just the phase comparator.

I also explained the output is a digital PWM output. Also explained in the data sheet.

By Samira TJBA
@ Sat, 2010-02-06 19:16

One cheap way is to use a CD4046 PLL. This cheap IC has a digital phase comparator. By feeding it the freqeuncy you want to detect on one input and the output of a phototransistor on the other input you get a simple PWM digital output that can easily be converted to an analog output if necessary using an RC filter.

-----thnx for the suggestion, When you say, feed the frequency we want to detect on one input, what do you mean? Can we do that using the twin t filter? Sorry if i sound stupid. The led we are trying to detect is on another robot which we are supposed to track.
 
thnx again for replying.
 
Also, we are using a Freescale HCS08 microcontroller and would like to generate noise using a speaker phone. We would like maybe 101-5 second noises when the robot is in contact with the other robot etc...actually this is part of our novel feature. We would like to do remote control too, but not sure whether thats suitable for our level of study.
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