VEMS Community Forum

VEMS => Configuration => Topic started by: gunni on April 29, 2011, 02:40:34 am

Title: Electronic det-cans you can make yourself on the cheap
Post by: gunni on April 29, 2011, 02:40:34 am
I wanted a easy to fit det cans that don´t require me to fit a knock sensor or fiddling with analog det-cans as many engines
are just horrible to fit these things to.

Analog det-cans

(http://www.scoobypedia.co.uk/uploads/Knowledge/detcans2.jpg)


So I remember my friend having a aligator clamp that is used to detect vibrations in suspension systems and such.
Basically a mic you can hook up to anything and then listen to the mic from within the car while you drive, this helps find bad bushings and or joint and so on.

I decided to make one for det detection.

Firstly I bought one of these microphones

(http://images.maplin.co.uk/full/qy62s.jpg)

http://www.maplin.co.uk/omni-directional-ultra-miniature-microphone-4566
Cost : 3.49 pounds

And one of these in black

(http://images.maplin.co.uk/full/l96bg_l97bg.jpg)
http://www.maplin.co.uk/50a-insulated-battery-clips-45675

Cost : 2.79pounds

And some MONO Mini jack extension lead of 2 or 3meters. I cut of one of the ends and soldered the microphone to the wires.

So total cost less then about 10pounds.

I then used a plastic glue gun and glued the mic to the aligator clip like so

(http://myndasafn.bmwkraftur.is/d/92953-1/28042011096.jpg)

And this is what it looks like finished

(http://myndasafn.bmwkraftur.is/d/92950-1/28042011097.jpg)

Now you still need heaphones so the choice there is yours. I bought some noise cancelling ones that didn´t work out as well
as I wanted but get some that are able to silence out as much outside sound as possible or maybe even little earplug ones and some
ear protection like so

(http://www.bestvalsup.com/v/vspfiles/images/ear-protection.jpg)


Now normally from the internet I have seen people buy little gadgets that allow them to connect the microphone and the headphones and then listen to the microphone.

However since you are going to be tuning with a laptop then I figured that connecting the mic to the laptop and then the headphones as well would be the easier solution, unfortunately the laptop I´m using at work for tuning has a bad mic input.
But I have tried this out with another laptop and the sound is as clear as day, If the engine is off I can hear gearchanges and throttle shutting.

I´m still missing a equalizer program I can adjust the microphone input to isolate some frequencies away for even better operation but
for now this will work just like analog det cans.

And with the laptop you can adjust the volume anyway you like.




Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: Sprocket on April 29, 2011, 04:05:49 am
 :)

Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: z0tya on April 29, 2011, 11:51:55 am
Is it better than using knock sensor with laptop sound processing (real time bandpass filter)?
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: gunni on April 29, 2011, 12:45:22 pm
It´s very similar to listening to the knock sensor using a knock box variant device
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: Sprocket on April 29, 2011, 03:18:05 pm
You cannot get better than the human ear at detecting knock, so long as you know what you are listening to. a perfectly running engine will have a nice crisp consistent tone, and an engine in knock has a random inconsistent tone.

http://theknockbox.com.au/the-knock-box/sound-recordings/
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: Sprocket on May 05, 2011, 02:21:37 am
This topic got me thinking.

The Knock Box I linked to above, is little more than a personal amplifier. Perhaps it is a little more sophisticated, but for the purpose of this topic I would think this http://www.rnid.org.uk/shop/products/listening_devices/minitech_with_stetoclips.htm is more than ideal for the job of analogue det cans.

I found this topic http://www.talkjdm.com/showthread.php?t=3284 which uses one of these with a little modification http://www.rnid.org.uk/shop/products/listening_devices/pocket_sized_listener_with_ear_bud.htm

Might be good if you are just looking for a simple amplifier with tone and base control rather than using it through the laptop.

This one http://www.rnid.org.uk/shop/products/listening_devices/bluesonido.htm has digital processing and background noise filtering similar to modern digital hearing aids, and from what the wife tells me, its like nothing she has ever experienced, to the point that she was freaked out for well over a week changing from analog to digital, but I digress. The benefit of this device is that it has a built in microphone that can be activated momentarally at the same time reducing the input volume on the external microphone, so that you can converse with some one (while you're still wearing your noise reducing head set)
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: mdlimy on May 09, 2011, 12:07:27 pm
cool write up, there are quite a few of these online.

why not just use an knock sensor as the mic?

i will be making one of these setups very soon, just trying to gather enough info to build it the best i can, i would like to run it into my laptop then listen off the laptop with headphones, anyone know if the laptop will alter the "raw" sound coming from the mic/sensor? If not, an eq program would work very well in this case also....also if the recording could be incorporated into the VEMS datalog, we would be in for a real treat ;)
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: boostd audi on May 09, 2011, 11:59:56 pm
i have seen knock sensor used with LED lights.  but having a microphone and a trained human ear and detect knock much better
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: rob@vems.co.uk on May 10, 2011, 01:45:49 pm
I've plugged a Bosch knock sensor into my laptop and used Audacity to record and play the noise through the headphones I've plugged in.
You can apply an FFT and make a band pass filter to strain out all but the knock frequency and its first two harmonics.
I did a little google for a real time FFT and found this:
http://www.fatpigdog.com/SpectrumAnalyzer/
It takes a bit of processing power - but you'd probably have the best DIY knock analyser out there...
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: mdlimy on May 15, 2011, 11:37:32 am
awesome rob, did you just use a two wire sensor wired straight to a mic jack? any need for an amplifier, or did did it sound/record well on the laptop?
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: rob@vems.co.uk on May 15, 2011, 02:44:53 pm
The two wires of the mic. cable were connected to the left and ground channel of the input jack.  The shield wire is grounded at the sensor end.
If anything the mic is a little too sensitive, you may want to check the impedence of the mic input and compare the impedence of the laptop.
I didn't and eveything worked fine, but YMMV.

Rob
Title: Re: Electronic det-cans you can make yourself on the cheap
Post by: boostd audi on June 11, 2011, 11:33:58 am
i bought one of these  $1.5 with wire
http://cgi.ebay.com/3-5mm-Hands-Free-Clip-Mini-Lapel-Mic-Microphone-New-/120732390755?pt=PCA_Speakers&hash=item1c1c361563

then a $0.40 clip,
wifey glue gun = FREE

total cost UNDER $2.00

then took the foam cover off and glued it to an aligator clipp..  works great

***they should incorperate mic in in VT so we can log it toooo


this is wayyy cool.. already done for you i bet you could use this as is
http://cgi.ebay.com/Hands-Free-Clip-Mini-Lapel-Mic-Microphone-3-5mm-2-5M-/110690223872?pt=PCA_Speakers&hash=item19c5a6c700