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DIY Knock headphones for standalone tuning


ucw458
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I built myself a set of knock headphones. It took about $20 worth of parts from radio shack. It works and is plenty loud through my headphones. The sensor is a nissan sensor for many early vehicles. Found on ebay for $10 new.

 

Now I can do some street tuning and play with the timing.

 

 

 

http://i463.photobucket.com/albums/qq352/ucw458/Knock%20Sensor/DSC03924.jpg

 

 

 

 

 

 

I used "Afrotechmods" video on op amps to build it. If you want to build one here are a few tips for this application. You don't need to power the knock sensor so omit that part. Also since you aren't powering it the filter part can be removed. (The 0.1 uf cap and 100k resistor.) The knock sensor has a chassis ground and signal pin. The knock sensor ground goes to the 9v battery ground setup in the video. For the gain resistors just omit the second one. That sets the gain to max. In the video the second one I'm talking about goes from signal output to inverting - in.

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Awesome! You could wire in an LED with (what I bet is another cheap and easy circuit to build) a threshhold of whatever voltage real knock is, so when it blinks, you could listen even more closely. I think with knock, since it happens quickly, it might even be too quick to tell the difference on headphones between background noise for a single knock.

 

That's kind of a guess, maybe it'll be super easy. I'm looking forward to your results.

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I need to do this. Is there a way to actually wire in a knock gauge. I know on DSM's when they use dsm link you can turn the factor boost gauge into a knock gauge.

 

I'll do a couple tests this afternoon. I'll let you know what I come up with.

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Here are the diagrams.

 

http://i463.photobucket.com/albums/qq352/ucw458/Knock%20Sensor/untitled2.jpg

 

http://i463.photobucket.com/albums/qq352/ucw458/Knock%20Sensor/untitled.jpg

 

 

Parts list

 

2x 220 uf capacitors

2x 1k ohm resistors

headphone jack

LM324 OP AMP chip (found at RadioShack)

5k ohm audio potentiometer

9v LED

double pole switch

9v battery clips

8-10' of shielded wire

scraps of 24ga wire

bare circuit board (breadboard, preferably with copper backing)

5"x2.5"x2" project box

Nissan knock sensor

Bosch EV1 injector clip

2 9v batteries

 

soldering iron + solder

 

Before making each connection wipe the soldering iron tip on a wet rag. This cleans the tip. Also try to get an iron with a small tip around 1/16".

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I tried it today and got alot of background noise. I had it bolted to the head and I could hear the valves. I'm gonna try again with the sensor in the stock location. I bet that will clear up the noise. I would have tried it sooner but everything was hot so I couldn't switch out the stock sensor without burning myself. I'll try again tomorrow.
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I'd suggest using the stock location for the knock sensor--who better than mitsubishi to know where to put it to begin with? Otherwise it's like having an in-car automotive stethoscope. That's why I just tapped into the stock knock sensor circuit on my Focus. Great write-up and info though and thanks for posting your method. When I get my car back from paint an body work I'll probably try to do what I did before and go through the radio etc for those of you who don't want to use the headphones. If you don't mind, UCW, I'll post it here eventually?
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Post it here if you want polarisman. That will keep all the info in the same place for people to read.

 

My amp has a headphone jack so it plugs into the radio easily using a tape converter or an aux input. I'm gonna do a video of it in the car playing over the stereo when I'm done with repairs. I just have to wire up the new knock sensor and change out my IAC. The current one isn't working right. But I have to remove the upper intake to do it.

 

I would have had it done yesterday but my roommates lebaron had a water pump failure. I had no idea how buried the water pump is on a 6g72.

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Does the new knock sensor have the same thread pattern as the stocker does? I'd gladly switch one out for the other seeing as how all the wires in my car are junk and I'm gonna have to pretty much re-wire the whole thing.
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No, my new knock sensor doesn't have threads. It just has a hole. Many cars use this sensor. Some have different connectors but the sensor is the same.

 

Our stock sensor has m10x1.25 threads. My new sensor only fits up to M8

 

 

 

This is the nissan version and can be found on ebay for $10 new. It's also the same sensor that professional built knock headphones use.

http://allworldautomotive.com/images/userphotos/10028_12365.jpg

Edited by ucw458
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I have but even with the amp it was really faint. The highest voltage I got from the nissan sensor was 1.2v. The nominal range was 700-900 miliamps. The range I got from the stock sensor was 40-80 miliamps with 80 being the highest voltage. The stock sensor just doesn't put out much voltage. The Stock ECU has an internal amp for raising the knock sensor voltage.
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I have but even with the amp it was really faint. The highest voltage I got from the nissan sensor was 1.2v. The nominal range was 700-900 miliamps. The range I got from the stock sensor was 40-80 miliamps with 80 being the highest voltage. The stock sensor just doesn't put out much voltage. The Stock ECU has an internal amp for raising the knock sensor voltage.

seting up a 2 transister amp circirt should give you all the voltage you'd ever need to hear the signal

 

I agree with Shelby. If you set up 2 inverting op amps to amplify the signal you'll be fine with the stock sensor. Most ICs are two circuits anyways. Use 2 audio trim pots to dial it in. One for gain and one for volume. No reason it shouldn't work the same as your Nissan sensor. I may get around to trying this out in the near future. Knock detection is crucial and I currently fail at it. Glad you kept this going UCW

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man it's been a long time but do you mean transister and not 'chip'

you do not use two of the same voltage transisters ,you need to match the 2'd transister to the out put voltage your expecting so the input will be within it's range , any way some thing like that it's been 30 yrs sence i play'd with circirts

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