tacho signal

[markey b]

is there a way of 'cleaning up' the tacho signal from a 5 gt turbo?

i've got a sequential shiftlight from a bike but the signal is crap to it

[Jimmy_GTT]

is there a way of 'cleaning up' the tacho signal from a 5 gt turbo?

i've got a sequential shiftlight from a bike but the signal is crap to it

Can you please explain what do you mean about 'cleaning up'?

[James5]

Maybe you could put a potentiometer inline

[markey b]

basically its not a clean signal, the shiftlight can't 'read' it, i think its the same for the lm-1 kit, and also i know ross aka hammond has a similar problem with his vapour dash...

its almost as if its ok for analog gauges etc. revcounter, but as soon as something digital tries to read it it gets confused, does that make sense?

[James5]

You will want to do something like my lovely 2 min drawing attached but you will get the idea.


You will need a 15k 3 way pot (couple of quid of ebay or pop into Maplins)

Then once you have done this to clean the signal to what you need you literally just adjust the pot.


Theoritically this should work as I had to do this on my 172 conversion and when I had an LM-1 with LMA-2 connection to get a better signal

[Scoff]

james that ignition live should be a ground. it may infact work that way but for the wrong reasons.

also the pins on the pot need to be correctly placed - if you connected the wiper to 12v and the outers to the tacho stuff then there may be some smoke :D

[Ian S]

http://www.rtoc.org/boards/showthread.php?t=6031

Would the above method do it?

[Scoff]

long winded way that is Ian, really only worth doing with the LM-2 since its tacho input is totally useless. doesn't even read a function generator properly!! The pot works OK with the LM1 as James says. I think the input on the innovate stuff is ac coupled and high impedance, so any noise on the input means it looses sight of the real levels. probably just some termination on the input would work fine also.

[markey b]

silly question, but how does a potentiometer work (in this application)

thanks for the replies by the way :)

[Scoff]

A pot/potentiomer is a 3 legged variable resistor. imagine you had a pot arranged so that one outer pin was connected to 10v and the other outer pin to 0v (ground). If you set the control to half way then you will read 5v on the middle (wiper) pin. If you set the control to 3/4 the way up you would read 7.5v. 1/4 the way and you would read 2.5v. you get the idea. the wiper just slides up and down the scale, so to speak. Thats assuming its a linear pot, some are logarithmic.

in the case of the LM-1 and LMA-2 mod, it is likely the noise on the tacho line is a big part of the problem, not just too much signal level. the noise will be HT noise, etc, so whilst the noise might read as high voltage spikes on the line it will be of very low current, in other words it doesn't take much resistance to sink it away, and so connecting the pot in the fashon described means that a lot of that noise will be removed. further adjusting the pot means that you can find the level at which the Innovate will start to read reliably.

A 10kohm pot, or there abouts, is what you want, arranged with the renault tacho signal on one side, ground on the other and the middle pin going off to the Innovate.

[Ian S]

Scoff, could you maybe find a moment to take the best bit's of this thread and add as an addendum to your existing page that I linked to above?

[markey b]

something similar to this:

http://cgi.ebay.co.uk/2-10k-POTENTIOMETER-Lin-variable-resistor-Linear-10-k_W0QQitemZ220347197787QQcmdZViewItemQQptZUK_BOI_E lectrical_Components_Supplies_ET?hash=item334db769 5b&_trksid=p3286.c0.m14

[Scoff]

Yes Ian, will try to remember to do it tomorrow.

[Ian S]

something similar to this:

http://cgi.ebay.co.uk/2-10k-POTENTIOMETER-Lin-variable-resistor-Linear-10-k_W0QQitemZ220347197787QQcmdZViewItemQQptZUK_BOI_E lectrical_Components_Supplies_ET?hash=item334db769 5b&_trksid=p3286.c0.m14

Exactly like that.

The wiper is the centre pin.

[Ian S]

Yes Ian, will try to remember to do it tomorrow.
:agree:

[markey b]

splendid.. just purchased said item... hopefully i'll be able to use my new old toy now, that i fitted ages ago but had to tape over as it was so erattic if got on my tits

[markey b]

just to bring this up, i'm finally about to wire it in..

i take it left pin is input, middle is to the 'device' and right pin is to ground?

[Ian S]

A 10kohm pot, or there abouts, is what you want, arranged with the renault tacho signal on one side, ground on the other and the middle pin going off to the Innovate.

So if by "input" you mean a feed from the Renault Tacho and by "Device" you mean to the Innovate, then yes. :)

And the Pot in the eBay add is not Log so either way around for input and earth is the same thing.

[markey b]

So if by "input" you mean a feed from the Renault Tacho and by "Device" you mean to the Innovate, then yes. :)

And the Pot in the eBay add is not Log so either way around for input and earth is the same thing.

cheers ian :)

device is a datatool sequential shiftlight, but same kinda idea :agree:

[olidaviesuk]

did you have any joy with this mark, have exactly the same shift light but couldn't get it to work for the same reasons.. was consigning myself to sticking it on ebay, but would rather use it as quite a cool little bit of kit :)

[Scoff]

But often it's not the R5's tach signal to blame. Infact it's pretty clean, instead some devices need to be wired straight to the coil negative post in order to function because they look for the back-emf spike from the coil. Mark if you can't get it to work with the pot then open the AEI, determine coil negative (the pin you would normally wire a rev limiter too) and stick it on that instead.

[markey b]

just getting round to do this, do I put the tach feed onto the coil neg?

[tiff_lee]

I used this with an astra gte digital dash and it worked for that.

[markey b]

wasit all over the place before?

[tiff_lee]

Yea it would just spike constantly from where the rpm actually was and would do the same when revving. Could take a small video clip showing before and after if you care to see?

[markey b]

yeah sounds good :-)
how do you know when it's adjusted or does it just settle it down

[tiff_lee]

Its immediately apparent when going from zero to max resistance, ill get a vid tomorrow.

[tiff_lee]

Ok got a quick vid not brilliant but hopefully shows the difference, in fact i'm not even sure if I wired mine up correctly now but meh.

Initially the pot is set nearly all the way to one end (if I go all the way it just zeros the tacho input) this is basically the same as not having the potentiometer fitted and the tacho is not very stable.

At 15 seconds I just the pot to the other end of the scale note the rpm actually increase although idle is the same, at 38 secs I adjust to other end of the scale (zero's output) then its back to going all over the shop.

http://i148.photobucket.com/albums/s4/tiff_lee_photos/th_VID00009-20101118-1427.jpg (http://s148.photobucket.com/albums/s4/tiff_lee_photos/?action=view&current=VID00009-20101118-1427.mp4)

[markey b]

you sir are a legend :)

i'll hook it up this eve and report back :agree:

[tiff_lee]

If only the women thought that...anyhow

I'm not sure how erratic the rpm readout is with your gauge but hopefully will be as effective, that was only using a 10k potentiometer as well.

[markey b]

http://www.datatool.co.uk/consumer/products/products/index.php?product=revlight is what i've got, if its still not working scoffs method is put signal to coil earth so i'll try that :)

[tiff_lee]

How much did they retail for? reason I ask is I saw a chap on another forum selling something similar he had made himself but it didn't seem all that cheap, his prototype cost like £80 or something.

[markey b]

i got it off ebay about a year ago, cost about £42 but never worked, had a bit of tape over it to stop it blinding me during its hissy fits lol

[markey b]

IT WORKED!

thanks all involved. 10k pot did the trick

just need to programme it now :cry: