Sharp IR Ranger noise!

Robofreak

Hello all,

I need some help with the noise that my IR ranger is making. I have an EmicTTS module hooked up to my bot along with the ranger, and whenever the Emic's not talking there is noise that is coming from the ranger, like a high-pitched beeping of about 15 beeps per second. How can I cancel this noise?

Thanks,
Robofreak

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Zoot

This sounds seriously odd (pun intended). Can you post a schematic or even a close photos showing how your components are setup and wired?

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Robofreak

I disconnected the wire from the audio amplification circuit that is connected to the Emic's AOUT pin and listened very carefully and I could still hear the buzzing from the Sharp. Then I disconnected the Sharp IR ranger and the buzzing stopped. It's sending out a strong radio signal as well as electronic noise in the circuit I think. I'll try to draw and scan a schematic of the setup then post it on here.

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Zoot

Seems like something might be amiss if the ranger is generating noise on it's own. What are you using to power the ranger? Is the power supply decently decoupled with caps? Voltage correct?

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When the going gets weird, the weird turn pro. -- HST

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Robofreak

yep, i'm using a 5v regulator from radio shack with a 100uf electrolytic capacitor on the output. the voltage is an even 5v.

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Zoot

Well a first guess is you are picking up noise from *somewhere*. Motors? But it still strikes me as supremely odd that you'd get audible noise out of the Sharp.

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When the going gets weird, the weird turn pro. -- HST

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Robofreak

well it's only audible when run through a sound amplifier with a speaker, not directly from the Sharp. Could it be the sample rate of the Sharp? A 'beep' every time the sensor does it's, sensing?

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Zoot

Sounds like your amp/speaker is picking up noise. Schematic? Photo of your setup?

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

Robofreak

Okay, here's the schematic. Sorry it's not drawn better, I just don't have any schematic software Note that the audio amplifier (LM386) circuit uses the same regulator output as the Sharp.

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

Zoot

I'll bet you're getting noise on the line. I would certainly put a .1uf cap on the power rails right at the ranger. Some users also put a 33uf between the output and ground on the Sharp rangers, but that's to cut noise in the analog out, not this kind of noise.

I would also put bypass caps .01 - 1uf (experiment) right at the power rails for the amp.

Lastly, that audio amp circuit is good for higher voltage (6-9v ideally, actually) -- you may want to try running the amp from your 7.2vin. You could try running the amp without the bypass cap between 1 and 8 (I'm wondering if you've got too much gain -- I've obtained plenty of volume w/o the bump in gain). Also, aren't you missing the series resistor w/the cap on pin 7?

For what it's worth, in noisy environments (like a 'bot) it took me some doing to eliminate noise in LM386 based audio amps. Short traces, tight connections, caps on power rails, all were necessary. Ditto proper routing (and sometimes shielding) of the speaker wiring (the wiring can act like a big antenna).

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

Robofreak

Hey thanks Zoot, you've been a great help. I'll try that out as soon as I can.

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Austin Bowen,

Robo-freak.com
www.livesoundforum.com

"One must watch out for mechanics. They start out with a sewing machine, and end up with the atomic bomb" - A quote from someone that I saw on Addall.com

mm

I 2nd the recommendation on moving the audio amp directly to the 7 volt input.

Either do this or add another regulator to the audio amp, you don't want the Ir stage and the audio amp stage running off of the same regulator.

Using separate regulators on individual stages is an effective way to isolate your DC supplies from feeding back to successive stages in your designs.


Mike