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TOPIC: Stabilization Circuit

Stabilization Circuit 5 years 3 months ago #330

I am having some trouble with a new project and was looking for some help.

Recently I worked on a project that utilized Sharp Distance Sensors, the Ginsing Shield, and an Arduino board. I am now working on a project that doesn't use the Ginsing Shield, but still uses the distance sensors. I am now realizing that there is a lot of noise coming from these sensors that I can't seem to get out. This wasn't an issue with the GinSing board, so I was wondering what is involved in the stabilization circuit on the Ginsing. Is there a schematic for just that section of the board? Any suggestions?
Last Edit: 5 years 2 months ago by administrator.
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Re: Stabilization Circuit 5 years 3 months ago #331

Hi peckcm, thanks for the question. I would suspect the noise wold be digital in nature since the LM386 in most applications has negligible noise outside the audio frequency range. The Babblebot IC is PIC81F, which is a programmable interface chip that is running at 10 MHz. The GinSing uses the "standard" 0.1 uF capacitor across the power connections at the Vcc/grnd pin connections to stabilize and filter the supply. The output of the Babblebot is in the 100 kHz range and is passed through a two pole lowpass filter to convert PWM to analog. So aside from aliasing effects caused by the sample rate, I might expect to see some EMF at 100 kHz, and 10 MHz, and diminisihing related harmonics. Do you happen to know what frequencies you see the noise appearing?
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Re: Stabilization Circuit 5 years 3 months ago #332

Well someone did post a video about this issue. So this is what the noise sounds like.



This noise occurs any time the sensors GND is connected to the circuit. Could it be the Ginsing's two pole lowpass filter that removes this noise?
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Re: Stabilization Circuit 5 years 3 months ago #333

It sounds to me that the chirp frequency seems about the same as the sample rate of the sensor. In your case how is the speaker connected?
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Re: Stabilization Circuit 5 years 3 months ago #334

The audio out is currently going out of Arduino Mega pin 11 through a lowpass filter and a Twin-T notch filter. Then directly out to a powered speaker. Is there something here that I could add to help remove this noise?
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Re: Stabilization Circuit 5 years 3 months ago #339

I wonder if there might be some current loop between the powered speaker and the Arduino circuit. It is powered speaker battery powered, and if so, could it be powered via the power available on the Arduino?
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