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Non-contact Trick to show magnetic field is controlled on COP -- Android

posted Jun 22, 2016 14:43:26 by AndyMacFadyen

Here is trick to find a COP coil primary that is not getting fired it will work on Android phones that have magnetic field detector. --- some phones have this sensor some don't.
It works on my Motorola Moto , but not on my HTC 626 or my Kindle Fire Tablet.
You will need to load a free app from Google Play Store "Magnetic Field Detector by Mobile Develop Team" .

Once you have the app up and running by using a magnet you should be able to figure out which end of the phone the magnetic sensor is located. On the Motorola Moto G it is located near the bottom edge of the screen.

Now with the engine running as you hold the phone over the engine the first thing you will detect is the huge magnetic field from the alternator but if you hold over an ignition coil you should be able to see the magnetic field firing pattern of the coil primary --- you will get a much stronger pattern if you do a snap throttle.
It is best not to actually touch the COP in case it has bad insulation on the secondary which could zap the phone.

It works much better if any engine covers are removed
This can also be used to detect if a relay or solenoid is energised, I tried it on a high impedance Bosch fuel injector but the pulse signal is very weak.
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[Last edited Jun 22, 2016 15:39:03]
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8 replies
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Tyler said Jun 24, 2016 01:23:13
Downloaded this, gonna try it out tomorrow!

Wonder why they included a magnetic field detector as standard on the phone...
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AndyMacFadyen said Jun 24, 2016 05:18:36
I think some phones use sensor for magnetic compass in addition to the GPS
This is just one of those crazy things that seem to work, how useful I don't know.
"Rust never sleeps"
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Tyler said Jun 26, 2016 01:09:07
Just tried it, can confirm it works on Toyota four-wire coils. Even unplugged one while running just to make sure it wasn't picking up other noise. Really surprised me, since these coils tend to be more heavily shielded than others.

Also tried it with the engine cranking (fuel disabled), still works well. Could be handy for no start diagnostics?

I could see this being useful for very quick testing before getting more sophisticated equipment out. OR if you're short on tools, but looking for some answers.
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MattWhite said Jun 29, 2016 13:31:14
Haha, I can imagine an uproar now. Customer watching us work through a doorway with a misfire. We pull out our phone, rest it on a coil, and charge an hours diagnostic time. Love it.
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Tyler said Jun 29, 2016 17:25:19
Oh yeah, that'd probably get some customers riled up in a hurry.

Thinking now, having a Bluetooth scanner dongle, combined with a Bluetooth scope, and you probably COULD do most diags with a phone!
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AndyMacFadyen said Jun 30, 2016 07:24:35
Bluetooth and wireless are they way things are going. There are and increasing number of bluetooth and wifi scan tools offering more than just basic OBDII access.

I tried a Velleman Wifi scope and found the concept worked on a Windows Notebook but the hardware wasn't capable enough and the Android App was unreliable, so I now use a labscope an Owon SDS with a battery pack that can connect if required to ethernet or a VGA monitor. I know of one decent looking 4 channel automotive wifi scope on the market the Carscope Pro
Link to manufacturers site
Link to UK based sellers site


[Last edited Jun 30, 2016 07:28:39]
"Rust never sleeps"
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MattWhite said Jun 30, 2016 13:57:53
The price on the carscope kit almost looks too good to be true.
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AndyMacFadyen said Jun 30, 2016 15:27:09
I have bought a few tools including couple of Autoditex items off Scantool-Direct I found them reliable although sometimes delivery is slow. The one weakness I can see on the Carscope Pro is there is no USB connetion to fall back on.

"Rust never sleeps"
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