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-   -   Cleaning up a mechanical VSS signal for the MPGuino (https://ecomodder.com/forum/showthread.php/cleaning-up-mechanical-vss-signal-mpguino-25144.html)

razor02097 03-07-2013 07:30 AM

Cleaning up a mechanical VSS signal for the MPGuino
 
1 Attachment(s)
As great as the MPGuino is there was one thing that drove me up the wall...

Driving along at low speeds was no issue. MPGuino read nice steady numbers. Get on the freeway and over 50MPH then the issues start... I would be going 110MPH then instantly 70MPH then 30MPH then 80MPH then 100MPH. The data generated was total garbage.

The issue turned out to be this Tracker I have has a mechanical speedometer with a magnetic reed switch to generate the VSS signal to the ECU. All is dandy and peachy at low speeds BECAUSE the MPGuino has a certain amount of filtering capabilities in it's software called VSS delay. However at higher speeds this will do no good because the reed switch bounces so bad it starts to fludder. Increasing the VSS delay can help mask the problem but if you add too much delay it will affect the data.

This calls for a filter circuit. I searched around and found a few threads on it, mostly Geo Metros. Some people suggested a few resisters some resisters and capacitors. I'll tell you what I did.

I took apart an old laptop charger and harvested a small inductor coil and a 3.3nf ceramic ac line filter capacitor from it. I soldered the VSS wire to one leg of the inductor and one leg of the capacitor. The other leg of the capacitor is wired to ground and the other leg of the inductor is the VSS wire that goes in the MPGuino.

My theory is the capacitor is small enough it won't screw with the VSS signal but enough to dampen bounce that occurs. The inductor is to help block any type of ac signals and interference that might sneak their way in to the unshielded wire. Here is a crude diagram...

http://ecomodder.com/forum/attachmen...1&d=1362659316

So far so good. According to the MPGuino the signal is steady up to 65MPH (speed limit on the interstate here....haven't gone faster yet)

Here are the other threads about VSS bounce for your reference...

http://ecomodder.com/forum/showthrea...-vss-6174.html
http://ecomodder.com/forum/showthrea...arm-15980.html



Motor on :turtle:

stargazerf3a 03-07-2013 12:41 PM

I get the signal from abs sensor and after 60 mph or 100 kph it gives rubbish information i did set the delay to 1ms but it does not solve my problem , i'll try your method although i would like to wait until you reach higher speeds...

razor02097 03-07-2013 12:53 PM

Quote:

Originally Posted by stargazerf3a (Post 360044)
I get the signal from abs sensor and after 60 mph or 100 kph it gives rubbish information i did set the delay to 1ms but it does not solve my problem , i'll try your method although i would like to wait until you reach higher speeds...

Do you know what kind of sensor it is?

If you can get the parts free like I did it is worth a shot. Unfortunately if I go faster than about 60mph my FE goes to shizzle.... Maybe today on the 70PSL downhill I'll try to give it a bump up to 70ish and see what happens.

AndrzejM 03-07-2013 02:45 PM

You can always glue a magnet to the main shaft and some kind of reed switch close enough to get pulses. You can use bicycle speed sensor even. It's hermetic, reliable and cheap :)

You can always use a simple diode and capacitor to filter signal. Low power diode anode to VSS sensor and 4.7uF 30V paralel to MPGuino. That should filter all the noise.

razor02097 03-07-2013 02:54 PM

Quote:

Originally Posted by AndrzejM (Post 360085)
You can always glue a magnet to the main shaft and some kind of reed switch close enough to get pulses. You can use bicycle speed sensor even. It's hermetic, reliable and cheap :)

You can always use a simple diode and capacitor to filter signal. Low power diode anode to VSS sensor and 4.7uF 30V paralel to MPGuino. That should filter all the noise.

I'm not sure noise was my issue I believe it was switch bounce. The cap between VSS and ground helps to dampen switch bounce so the MPGuino only sees one edge on each pulse.

AndrzejM 03-08-2013 04:56 AM

If you have access to oscilloscope you may see what's the issue there. But if switch is bouncing that may cause ECU to work incorrectly. Maybe you should take a closer look at your VSS switch.

stargazerf3a 03-08-2013 05:45 AM

Guys problem solved , one day I've accidentally removed the power from the mpguino before it saves to eprom and every configuration lost, so i've entered pulses per speed and micro sec per liter that and forgot configure vss delay that was 2ms by default :confused: oooodd... Speed is now right except when i run over bumps and potholes (all the time Greek roads :rolleyes:) , then speed goes instantaneously nuts... That maybe is not a big issue...I'll try your solution, i have a lot of spares from power supplies so...

AndrzejM 03-08-2013 05:54 AM

Quote:

Originally Posted by stargazerf3a (Post 360260)
Guys problem solved , one day I've accidentally removed the power from the mpguino before it saves to eprom and every configuration lost, so i've entered pulses per speed and micro sec per liter that and forgot configure vss delay that was 2ms by default :confused: oooodd... Speed is now right except when i run over bumps and potholes (all the time Greek roads :rolleyes:) , then speed goes instantaneously nuts... That maybe is not a big issue...

It shouldn't be like that, with MPGuino going nuts over bumps. Check VSS cables, from the sensor to the dashboard and MPGuino. You've mentioned before that you gest VSS signal from ABS sensor, right? So you should check ABS cables then. But I don't think that plugging into ABS signal is a good idea. You can get some false signals and that can mess up your safety. It's better to fabricate VSS sensor by gluing a magnet to the drive shaft than mess up with ABS. IMHO :cool:.

stargazerf3a 03-08-2013 06:25 AM

Quote:

Originally Posted by AndrzejM (Post 360261)
It shouldn't be like that, with MPGuino going nuts over bumps. Check VSS cables, from the sensor to the dashboard and MPGuino. You've mentioned before that you gest VSS signal from ABS sensor, right? So you should check ABS cables then. But I don't think that plugging into ABS signal is a good idea. You can get some false signals and that can mess up your safety. It's better to fabricate VSS sensor by gluing a magnet to the drive shaft than mess up with ABS. IMHO :cool:.

No vss sensor and cables exist on my car except abs sensors and speed information travels from abs computer through the multiplex network to the whole car , i don't think it is practical to intercept that although i've tried to. Yesterday i've used abs twice due to the heavy raining and it worked perfectly as always. Though my intention is to either put a speed sensor to the gearbox from and older clio2 version of fabricate a sensor as you said but that would be extremely difficult due to the fact that drive shafts are very small and totally exposed to the elements (a belly pan could help a lot)

AndrzejM 03-08-2013 06:35 AM

I think that you have a VSS sensor
http://i11.photobucket.com/albums/a1...8012011675.jpg

It's a Kangoo picture (not mine), but as far as i know Kangoo and Clio have the same engines and gearboxes.

stargazerf3a 03-08-2013 06:54 AM

Thank you that is really kind :thumbup:

I am aware that this sensor exist but not on late clios and kangoos there is only a fake sensor to cover that hole and does not have cables and such.
When i first tried to hook up the mpguino i took the service manual and searched the pin that vss sensor hooks up to the ecu and guest what, nothing there just a little rubber cap. So i've downloaded an newer version of the so called Renault dialogys and read about this feature they did to newer versions to reduce the amount of cables and connectors and that is true, half of the pins on the ecu are not used. So i has thinking that i can install a real sensor to the gear box that will be used only by the mpguino and consoluino (for cruise control maybe).
But i can not say it is cheap...
SPEED SPEEDO SENSOR RENAULT CLIO SPORT 182 172 2.0 16v LAGUNA MEGANE SCENIC 1.9 | eBay

razor02097 03-08-2013 06:56 AM

Quote:

Originally Posted by AndrzejM (Post 360258)
If you have access to oscilloscope you may see what's the issue there. But if switch is bouncing that may cause ECU to work incorrectly. Maybe you should take a closer look at your VSS switch.

It is just a simple reed switch. I don't think the ECU is as sensitive to SB as the MPGuino.

AndrzejM 03-08-2013 06:59 AM

Quote:

Originally Posted by stargazerf3a (Post 360271)
Thank you that is really kind :thumbup:

I am aware that this sensor exist but not on late clios and kangoos there is only a fake sensor to cover that hole and does not have cables and such.
When i first tried to hook up the mpguino i took the service manual and searched the pin that vss sensor hooks up to the ecu and guest what, nothing there just a little rubber cap. So i've downloaded an newer version of the so called Renault dialogys and read about this feature they did to newer versions to reduce the amount of cables and connectors and that is true, half of the pins on the ecu are not used. So i has thinking that i can install a real sensor to the gear box that will be used only by the mpguino and consoluino (for cruise control maybe).
But i can not say it is cheap...
SPEED SPEEDO SENSOR RENAULT CLIO SPORT 182 172 2.0 16v LAGUNA MEGANE SCENIC 1.9 | eBay


You can always try a local junkyard :)

AndrzejM 03-08-2013 06:59 AM

Quote:

Originally Posted by razor02097 (Post 360272)
It is just a simple reed switch. I don't think the ECU is as sensitive to SB as the MPGuino.

If you say so :thumbup:

stargazerf3a 03-08-2013 07:17 AM

Quote:

Originally Posted by AndrzejM (Post 360273)
You can always try a local junkyard :)

Of course tomorrow is a day off :thumbup: time for ecomodding :turtle:

stargazerf3a 03-08-2013 07:20 AM

Quote:

Originally Posted by AndrzejM (Post 360258)
If you have access to oscilloscope you may see what's the issue there. But if switch is bouncing that may cause ECU to work incorrectly. Maybe you should take a closer look at your VSS switch.

Maybe mine is too cause abs sometimes feels like it locks the wheels a little when i am on a bumpy spot but that is just a reading from my butt-o-meter :D

I'll Try junk yard tomorrow that is a day off :thumbup: ecomodding day :turtle:

AndrzejM 03-08-2013 07:23 AM

:thumbup:Good luck!:thumbup:

razor02097 03-11-2013 07:29 AM

I have tested this mod at 70ish. The speed reading is stable. There is no jumping or interference also it didn't mess any of the PPM or microsec/gallon settings up.

I would say mission accomplished :thumbup:


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