AEM UEGO rings at 14-16khz and it is driving me nuts. - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 05-30-2016, 12:13 PM   #21
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Quote:
Originally Posted by hi_im_sean View Post
Have you measured current draw yet?

Im a little rusty on filter design, but shouldn't you get input impedance first? based from current draw... or have you?
On the list to do today. but for filter design, bigger caps/coil are always lower frequency, and that means more filtering at the 5khz or so I am trying to filter. So my design for this will likely be "bigger is better".

I am super rusty at filter design as well so...
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Old 05-30-2016, 12:16 PM   #22
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True, as long as you get the crossover frequency below 5k. Which I would want to calculate out to be sure, because troubleshooting yada yada


not like you need help here, but here-
RC Low-pass Filter Design Tool
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Old 05-30-2016, 12:42 PM   #23
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Quote:
Originally Posted by hi_im_sean View Post
True, as long as you get the crossover frequency below 5k. Which I would want to calculate out to be sure, because troubleshooting yada yada


not like you need help here, but here-
RC Low-pass Filter Design Tool
It dumps about 1amp through it's ground output.

That's a handy tool, gonna book mark that one.

Using the DCR of the inductor I have (since that one only does RC filters, and an inductor will only improve the situation) of 0.8ohms and a 0.022F cap, it is -40db by 1khz. Only problem is, this seems to limit the current on the ground of the meter to 0.3-0.4 amps rather than the 1amp it was doing before. I think I will just go with the cap for now.

I have a video showing the current draw and effectiveness of the capacitor, but my internet is slow and it will take about an hour for it to be up...
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Old 05-30-2016, 01:20 PM   #24
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So impedance will be whatever voltage is in ohms. Call it 13.5 ohms.

I just linked the RC, scroll down on the left of the page for the other links, it does ALLOFTHETHINGS

RCL LPF

Bookmark the main page
http://sim.okawa-denshi.jp/en/
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Old 05-30-2016, 01:39 PM   #25
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Give yourself 20 years and you won't be hearing it.
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Old 05-30-2016, 02:08 PM   #26
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I put the cap in, wired everything up and ran the new B+ for the radio. It all works, noise floor is now acceptable through the stereo system and the head unit no longer rings internally. Just used the 2200uf cap. It's 35v at 85C, should be ok in the dash board. I will design/make a nicer filter sometime down the road.

Quote:
Originally Posted by hi_im_sean View Post
So impedance will be whatever voltage is in ohms. Call it 13.5 ohms.

I just linked the RC, scroll down on the left of the page for the other links, it does ALLOFTHETHINGS

RCL LPF

Bookmark the main page
Engineering Design Utilities
That is a handy site! My brain was apparently elsewhere before.

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Originally Posted by DNMakinson View Post
Give yourself 20 years and you won't be hearing it.
I do try to wear earplugs when I can at least. Hoping for it not to be like that, though it seems I am limited to 18khz now. Use to be I could detect (didn't quite sound like a tone) up to 22khz.

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Old 05-30-2016, 02:33 PM   #27
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In all seriousness, my son makes his living primarily as an audio engineer. He really protects his hearing, and has kept his high frequency. I lost the ability to hear 18k flybacks about 10 years ago.
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Old 05-30-2016, 04:48 PM   #28
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Mount a 2,200 uF / 25V low ESR capacitor on the 12V and power ground wires, close to the AEM controller.
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Old 05-30-2016, 05:10 PM   #29
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Quote:
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Mount a 2,200 uF / 25V low ESR capacitor on the 12V and power ground wires, close to the AEM controller.
That is exactly what I ended up doing.
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