DIY electronic knock sensor UPDATED with PICs/Instructions

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wannabethestig
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DIY electronic knock sensor UPDATED with PICs/Instructions

Post by wannabethestig »

Builit a little knock sensor and it turned out ok... Less than $20 and an hours worth of work. Just make sure that you mount the microphone flat or else you will hear a bunch more than your engine internals.

http://youtu.be/6-Tje46_JZI

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Last edited by wannabethestig on Mon Apr 01, 2013 6:02 pm, edited 1 time in total.
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ashy-larry
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Post by ashy-larry »

Haha, that is incredibly innovative. It sounded pretty clear too! I also was eventually going to get a knock light but you MAY have turned me on to this.

Good job dude
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Post by sdaigle240 »

sold. STICKY STICKY STICKY THIS. knock lights are trash, this is awesome.


can you make that pic bigger so i can see the lables, thanks! cant wait to do this asap.
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Post by LPime001 »

This is awesome.

Do you have any pics of the finished product uninstalled?
I know this is probably super simple, but would you be willing to do a step by step with pics?
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Post by wannabethestig »

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Purchase microphone, 1/8" mono plug, extension cord for earphones from radio shack. You can use either the mic that you soder to or the one that has the leads. Buy a 2ga brass terminal, (if I could of found a bigger one I would have used it), heat shrink from any auto parts store. Make sure that you have some type of epoxy or superglue.

Tools, jewlers screwdriver if using the two piece method, sodering gun and solder, vice (or vice grips) , drill and bit, hot glue gun (optional), lighter or heat gun, wire strippers,

1. Flatten out the 2ga terminal with a vice so that only about a 1/4" is still round. I did it with vice grips but I would definately recommend a vice.

2. Drill into the round portion so that you can thread the leads through.

3.Thread the leads throu the hole. if you have the mic with the leads so they are out of your way

4. Glue the microphone to the flat porteion of the brass terminal. Enough so that the listening portion (flat black part) of the microphone is completely encapsulated by the glue/terminal.

5. Take apart the plug.

Info... There is two ways to go from here... I made one where I cut the extension cord and wired it directly to the microphone. (less connections/things to go wrong or add noise) Or you can install the whole plug and then connect the plug to the extension. I've pictured both ways.

One piece method.

6a. Cut the extension cord at the female plug. strip out the outer insulation keeping the shielding intact, strip 3/8" from both wires.

7a. Thread the extension wires through all the parts of the plug (except the male portion which is not used) and either soder the wires to the terminals or the leads on the mic. Make sure the shieldeing comes in contact with the plug body when you put it together.

2 piece method

6b. Thread the male plug parts over the leads.

7b. Wire the leads/install 2.5" leads with 24ga wire. Connect the wires to the terminals on the plugs.

Once everything is connected, this is a good time to test that everything works. I just plugged it into my computer and tapped the mic. If you can talk into it and hear your voice then you dont have a good enough seal between the mic and the 2ga terminal.

8. Push the assembled plug into the 2ga terminal and you can either crimp it or glue it if you want.

9. Install heat shrink.

10. optional... you can install some hot glue over the top side of the microphone where the leads come out so that it protects that area or get enough shring tubing to cover it up.

11. Listen to the sweet tunes of your KA-T.
My wife "haven't you spent enough time and money on that car yet?" my answer "no"

The build thread-> viewtopic.php?t=58421&highlight=
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Post by airman »

Stickied! You could take it a bit further and build some sort of amp/filter box so you wouldn't need the laptop.

Everyone should consider this. Knock is certainly a leading cause in engine death and this will allow you to know exactly what's going on inside of your engine.

I think the only thing I would worry about is something happening to the mic because of heat.
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Post by wannabethestig »

Thanks for all the nice comments... I didn't invent the idea but I did modify it a bit. Couple of other tidbits.

1. Instead of buying the mic, you can get one of those cheap ($12) "personal listening devices" Remove the microphone, lengethen the wires to the mount like i have and then mount the device behind the dash or in your seat or whereever. Then you can plug earphones directly into it and you don't need a laptop or stereo to amplify the signal. Think racecar!

2. Use a equalizer on your computer to adjust the gain up at 6khz and down everywhere else. This is what our engines' knock frequency is around. I have the equasion to figure out the exact frequency somewhere if someone's interested but 6khz is close enough imo.
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Post by 8-bit »

sticky this!
http://www.areasoundmusic.com

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Post by airman »

I have stickied this but I do not have access to the Hall of Fame section :/
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Post by beercandrifter »

you know, you could easily route the mic output through a bandpass filter and use the output of the bandpass filter to feed a diy sound level amplitude meter like this http://www.nerdkits.com/videos/sound_meter/
even comes in a nifty kit

would save you having to listen to it. could just see when its spiking.

heck you could make it all in a self contained project box that you could just plug the 1/8 jack into. would be fun to work on something like that if you guys would be interested.
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Post by sdaigle240 »

yes. wires terrify me. gonna make this thing very soon but ultimately i do want it to plug directly into a set of head phones
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Post by dj_smooth »

I tried this, but it didn't work for me. I tried to skip the laptop and go straight for the head unit. Do you need the mic input from the computer and then back out in order for this to work?
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Post by wannabethestig »

I did... there is a line amplifier or something like that so you could go straight to the deck or a set of ear phones. Look up personal listening device.
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Re: DIY electronic knock sensor UPDATED with PICs/Instructio

Post by whitenoise »

this is genius, i should make one for my car since this heatwave is causing my ka-t to run a lot hotter than usual
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Post by airman »

dj_smooth wrote:I tried this, but it didn't work for me. I tried to skip the laptop and go straight for the head unit. Do you need the mic input from the computer and then back out in order for this to work?
Yes. An unpowered mic cannot produce an amplified signal - but the laptop/listening device/standalone amplifier circuit can.

Beercan - I LOVE the idea of the equalizer hooking into the sound meter. Go further and be able to adjust the gain going into the display so you can calibrate it to your knock threshold.
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Re: DIY electronic knock sensor UPDATED with PICs/Instructio

Post by drunknmunky »

Thanks for the post mate.
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Re: DIY electronic knock sensor UPDATED with PICs/Instructio

Post by schmauster920 »

I have a lot of the parts to do this... considering tapping it into my AUX input so i can crank it up and bump my engine noises.
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Re: DIY electronic knock sensor UPDATED with PICs/Instructio

Post by wannabethestig »

Do it!!!
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The build thread-> viewtopic.php?t=58421&highlight=
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Re: DIY electronic knock sensor UPDATED with PICs/Instructio

Post by adamky »

I made my own several years back using similar parts from radio shack: viewtopic.php?f=36&t=43581

There is a program called Audacity that actually does a full spectrum graph of the sound. Using the graph, you can actually see where you experienced knock.
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