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I am using Pololu's sharp infrared sensor board part# GP2Y0A60SZLF and I am trying to minimize the noise caused by the sensor on the voltage supply as much as possible.

I have made a filter and voltage regulator circuit as shown below, The IR sensor and the filter PCB are directly connected together. The output is carried out via a wire 7" long from the filter circuit as shown to a main PCB that has another RC filter (R2,C10) filter schematic Here is the scope shot at the 6-12v supply terminal. The spikes below are 1khz, 46mv p-p. Scope Probe VDD

What do you suggest to clean the supply line below?

I am also including the waveform on the sensor output.

Sensor Output

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  • \$\begingroup\$ Normally I would have a really had time caring about 46mVpp of noise on the input of a regulator. Does it actually make its way to the output? Is it really a problem, or are you trying to minimize it to minimize it? \$\endgroup\$
    – Matt Young
    Commented Feb 16, 2016 at 18:51
  • \$\begingroup\$ Hi Matt, it does make it's way to the output and that's one problem. I am planning to build 12 of these feeding off from the same supply line. Right now I can only turn on one at a time because of the noise I would get on the supply line. If I can manage to clean out the supply line as much as possible then I can turn on all sensors at the same time. \$\endgroup\$
    – Rocky79
    Commented Feb 16, 2016 at 19:02
  • \$\begingroup\$ In your schematic you say "scope probe sensor VDD", but isn't your sensor VDD really at C8? What does the voltage look like there? \$\endgroup\$
    – DigitalNinja
    Commented Feb 16, 2016 at 20:11
  • \$\begingroup\$ @DigitalNinja What matters to me is the effect of the sensor on the power line which is the input of the regulator. I will have to check the scope output at C8. \$\endgroup\$
    – Rocky79
    Commented Feb 16, 2016 at 20:16
  • \$\begingroup\$ Okay, I thought you were worried about it the other way around (the input power affecting the sensor output) - which is what I think would be a normal concern. \$\endgroup\$
    – DigitalNinja
    Commented Feb 16, 2016 at 20:19

1 Answer 1

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This sensor draws like 300mA in bursts, likely you can see that on the power. I have had a similar problem with driving servos, which made huge spikes on the power line when powering from a lab psu.

I suggest to:

  • power this all with a battery with small internal resistance, i.e. alkaline AA cells, or LiPo
  • increase c3 to at least 470uF or 1000uF
  • (might try LC filter on the power lines)

The output signal is not bad with 30mV of noise. Your idea of the RC filters look correct. I'd give also a try with bigger C and smaller R, like R of not more than 1k, and C of some microfarads.

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  • \$\begingroup\$ Thank you for the suggestion. I ended up turning on one sensor at a time rather having them all on ( 12 sensors). The 30mv noise was acceptable for my application, so it turns out it's not too bad. \$\endgroup\$
    – Rocky79
    Commented Mar 17, 2016 at 23:45
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    \$\begingroup\$ Oh 12 sensors x 300mA! That is quite a load with spikes! Glad you made it working! \$\endgroup\$
    – Gee Bee
    Commented Mar 18, 2016 at 0:21

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