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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Club Member
Location:
sydney
Registered:
May 2002
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 06:09
 
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itd be easier if you just changed the resolution to make the signal look better 
good stuff dude .... more self test before asking dumb questions I say!!! youve done well!
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Location:
Hobart
Registered:
June 2002
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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I Supported Toymods
Location:
Glenmore Park, NSW
Registered:
March 2004
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 11:32
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ah so tach signals are prone to engine noise just like a stereo?!
might be why my tach drops signal randomly all the time.
so if i use a good shielded wire i should see better results?
would any sort of resistor help in my cause (just running std 2t) or are they more just advantagous for ecus etc?
cheers
Nathan
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 12:41
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well, tach signals are prone to noise from both spark plug wires and other sources of noise like alternator (but are usually far away from them)
i don't think a tachometer has as much of a problem with signal noise, but it does depend on the type of signal it gets.
i found that even running a 1K resistor caused my KE15 tacho to function intermittently and the needle dropped often.. so addign a resistor reduces the size of the signal, and the effectiveness of the tacho.
for the ECU, it depends on the type of signal it is expecting..
if it expects a clean 12V squarewave, and it gets a coil -ve input, it will likely need a bit of conditioning..
i am not running a shielded wire to my tacho, but i am to the ECU.
CYa, Stewart
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Location:
Victoria
Registered:
May 2002
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 12:58
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yar, i have my eye on one of those... if i didn't have a brand new elec dizzy i'd try that.
you could also use the HEI as 'coil ignitor' and rather than ground the coil, ground a pull up resistor, similar to how the hall effect ones are used... (i'm a bit fuzzy on that  )
many ways to skin the tach cat...
i'll test the 'tach output' with and without 15K resistor soon and get more graphs 
i'll probably end up using the VR dizzy, soem generic VR ignitor to trigger MS, then another ignitor for the MS2 spark output.
Cya, Stewart
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Location:
Victoria
Registered:
May 2002
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 13:15
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if i was to get hold of a 2tg elec dizzy my plan was to use a bigport igniter&coil to do the VR shaping and advancing
Looking at the toyota ignitor document and msns diagarms the 7pin GM one performs the same stuff as the bigport igniter
One of the Mr2 guys has this worken on his aw11 now
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Location:
Hobart
Registered:
June 2002
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Re: testing Jaycar HEI tach signal for Megasquirt
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Fri, 10 December 2004 23:13
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nah i never tried dave cap, i didn't think it would help my problem since my spikes weren't higher than my highest operating rpm anyway (don't want to filter out that frequency  )
my hardware is standard with r10 changed. (oh and q1 mounted on case, caus' im running low-z injectors with pwm, fried q1 once)
i think there may be some slight differences between the tach filtering done in software between the diffeent firmwares. It could just be that the filtering is performed asynchronously and timing it effected by the extra features in the code (msns-e has a bucket load). I'm pretty sure msns-e has that false trigger filter. Hopefully i will get spark control going over this christmas.
in those emmebedded graphs u just posted - When running HEI, are you triggering from tach signal or -ve coil terminal? probably coil signal, because i dont think the tach signal works with those high value resistors since it is only a 12v signal. I have never run megasquirt without HEI so i can't really say.
Do you have a condenser on the coil? maybe without HEI the dwell time is smaller and therefore the primary ringing is larger and causing extra triggers. By lifting the resistor probably increases the threshold which will trigger megasquirt. Dunno, all just guesses. I would love to investigate more with an oscilloscope.
its good that you tried a bunch of values, i just stopped once it worked well, lol. I dont think higher values of resistors will effect your maximum rpm (unless your spark gets weak at high rpm with less dwell time). The dave cap will turn the input into an RC filter dropping out high frequencies depending on the value of R and C.
Oh btw how did you increase the sample rate of the data logging?
cheers
Chris
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Sat, 11 December 2004 02:29
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hmm, yeah i didn't really want to try different values of Dave cap.. just stuck with 0.22 (as it was tested in V8 to whatever rpm, and was going to be implemented in the V3 PCB)
you have a flyback board? are you running TIP42? flyback with 2xTIP42's will increase the flyback capability by 3 times over a single TIP32.. ( i think )
yup, from the coil -ve as it is easier.. i've put the tach output into my HEI now and will be testing with and without resistance on the tach output on monday. be interesting to see how it is affected... i'm not totally clued up on the whole tach input/output signals.. and scope would be damn handy
hmm, i figured it was something like the resistor was changing the time taken for the dave cap to charge... increasing it's smoothing effect on signal.
no, i have condensor on the points... which now thinking about it, is the wrong place
since both condensor and dave cap are 0.22uF i figure they are doing the same thing...
decreasing the comms speed to 20ms.
Cya, Stewart
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Mon, 13 December 2004 03:57
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tried the HEI tach output.
seems to be pretty good up until 6000rpm, then i get a couple of small glitches.... i think i'll do an extended datalog (like 30mins... other ECU's would love to have that option ) and go thru and see how stable the signal is..
otherwise, it ill be resistors coil -ve.
looking at the schematics, it doesn't make sense to change R10 IF you have the Dave cap... the Dave cap is before R10, so it absorbs noise before R10. if i put resistor before dave cap (as i was testing) then it slows the charging rate of dave cap...
since i'm using microphone cable and RCA plugs for tach input, i'll just make a short 'resistor lead' so i can swap it out easily..
Cya, Stewart
ps, seems the KE15 tach is reasonably accurate.... up to 7500rpm anyway
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Location:
Hobart
Registered:
June 2002
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Re: testing Jaycar HEI tach signal for Megasquirt
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Mon, 13 December 2004 23:31
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yeh that sounds similar to my problem using the tach signal. glitches in high rpm.
what you say about r10 is correct. it still has some effect though, a number of people have reported it helping. By putting the resister b4 dave cap you are making an RC filter and changing the value of either R or C will effect the filter cut off frequency. but r10 is probably just effecting the amplitude of the signal, which then affects when the john diode conducts??.. anyway best way is to try things like you have.
yeh i was impressed with my RA40 tacho aswell, accurate right up to a tad over 7000rpm
cheers
Chris
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Tue, 14 December 2004 06:09
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ok, heres the final graphs
http://www.materials.unsw.edu.au/~sford/tach-testi ng2.html
the top 3 are taken directly from the Jaycar HEI "tach output". there is a little bit of noise in there. max of about 300rpm?
the bottom two are taken directly from the coil negative terminal, but with a 15K resistor in series between the coil and the MS.
i think the bottom two are better quality and more accurately track the rpm of the motor..
so whatcha think?
Cya, Stewart
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: testing Jaycar HEI tach signal for Megasquirt
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Tue, 14 December 2004 06:12
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from this
to this with just a 15K resistor...
compared to this (from HEI tach output)
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), i haven't got one of my latest setup since some bastard stole my laptop. I think its smoother than this now, new points and the resistor helped a treat.