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-   -   VSS limit (https://ecomodder.com/forum/showthread.php/vss-limit-29787.html)

alexander.foti 08-20-2014 03:59 AM

VSS limit
 
Hi all

I have tapped into the VSS signal from the clocks on my NC700.

I have my pulses per mile set to 120000. If I set my vss delay to 2ms it reads up to 10mph only.

1ms reads up to 38 mph only.

0ms reads up to 78mph, after that speed it starts going down until it reaches 0.

The bike has a VSS which is a hall effect sensor.

Any ideas? I would really hate to have to add a reed switch and magnet as its very messy on the bike :(

Thanks in advance!

alexander.foti 08-20-2014 11:30 AM

Just had a longer ride today, after a quick tweak half way through, the mileage tracking is spot on with the clocks which is great!

I have to have my VSS delay set to 0ms otherwise it isnt accurate (as per my prev post).

I had a thought, my VSS pulse is 0-5v and is being generated by a hall effect sensor in the gearbox. I would be very suprised if my inability to detect above 78mph is due to signal noise, but instead due to the voltage?

If I can generate 0-12v instead of 0-5v from the clocks, does anyone know if it will get any better?

alexander.foti 08-20-2014 02:49 PM

If it is an issue of too many pulses, I am thinking of using a pulse divider with a CD4027 and powered by a 5v regulator:

http://i1057.photobucket.com/albums/...psd082f1e7.jpg

pin 3 will be from the VSS sensor on the bike rather than the "ignition coil" like in that diagram.

P-hack 08-20-2014 04:56 PM

that is a lot of pulses, given the delay changes the top speed then that seems like the problem. A dedicated atmega chip might be able to keep up with it, but not one that is monitoring injectors and displaying data on an lcd and keeping running 64 bit tallies. I would divide by 24, that is every time the vss edge changes 24 times, toggle the output pin, set pulses to a sane 5000/mi. Lunch off the existing 5v supply and intercept the vss, no oscillator required if vss is interrupt driven. @ 8mhz you have about 3000 cpu cycles to sort each edge out @ 78mph.

Or use a gear sensor and some ferrous screws on a wheel.

alexander.foti 08-20-2014 04:59 PM

Quote:

Originally Posted by P-hack (Post 441359)
that is a lot of pulses, given the delay changes the top speed then that seems like the problem. A dedicated atmega chip might be able to keep up with it, but not one that is monitoring injectors and displaying data on an lcd and keeping running 64 bit tallies. I would divide by 24, that is every time the vss edge changes 24 times, toggle the output pin, set pulses to a sane 5000/mi. Lunch off the existing 5v supply and intercept the vss, no oscillator required if vss is interrupt driven. @ 8mhz you have about 3000 cpu cycles to sort each edge out @ 78mph.

I would say thats the issue as well, although I would like somebody who is experienced with the code to let me know if it is.

Surely I can just use a freq divider on the VSS signal to keep it seperate from the mpguino? Im no good with IDE like the arduino, and OK with electronics (if following instructions :) )

meelis11 08-21-2014 03:49 AM

Hi,
check my topic, I had speed jumping problem and I added capacitor to all my boards to smooth out speed-jumping
http://ecomodder.com/forum/showthrea...5-a-21984.html

Maybe you could try to remove that capacitor near input pins and resistors - it has 103 written to it. Probably you have so many pulses (normally pulses/mile is between 4000 and 10000) that capacitor is smoothing pulses to steady voltage.

Meelis

alexander.foti 08-21-2014 03:57 AM

Hmm yes I see what you mean, it is a lot of pulses compared to everybody else.

I have already implemented the device into a watertight housing. I would have to destroy the case to get back to the pcb (stupid I know!).

Do you think dividing the pulses before it enters would also solve the problem?

meelis11 08-21-2014 04:50 AM

Probably dividing pulses works, but removing one capacitor may work too, maybe not. But I understand if you dont want to destroy your enclosure. So if you laready have parts to make pulse divider then you could try it.

Can you post pics? would be nice to see how you made watertight enclosure.

alexander.foti 08-21-2014 04:51 AM

Quote:

Originally Posted by meelis11 (Post 441446)
Probably dividing pulses works, but removing one capacitor may work too, maybe not. But I understand if you dont want to destroy your enclosure. So if you laready have parts to make pulse divider then you could try it.

Can you post pics? would be nice to see how you made watertight enclosure.

Of course, when this is all finished, I will do a whole write up with pictures, in case anybody else wants to do the same install on a NC700 :)

alexander.foti 08-21-2014 10:08 AM

Have come up with the following:

http://fotifixes.com/imagehosting/im...withcap_v4.png

Lets see if it works. This should divide the pulses by 16.


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