Author Topic: Tach  (Read 106409 times)

Reply #15February 20, 2006, 03:33:47 am

regcheeseman

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« Reply #15 on: February 20, 2006, 03:33:47 am »
Hi,

So leaving the red line was my fault   :oops:

I wasn't too concerned about copying your gasser tach too closely as it seemed to be of a different design.

I have a gas tach open on my bench here and I could see that it bore more than a passing resemblance to the diesel tach circuit you posted. There is no diode on my gasser tacho.

Swapping the gas components to the diesel equivalents should be fairly easy now...doable on the same board.

That chip orientation (component side view) is standard practice over here, is it conventional to view designs solder side where you are from?

That pin 7 is no longer causing me concern, it was the end of the week - my brain had had enough by then!

I have shown electrolytics on my schematic and am guessing that C1 and C3 are electrolytics on the TD schematic.

I'm going to rework the TD diagram to match the gasser one....hold fire on the printing!

Cheers!

Reply #16February 21, 2006, 03:24:47 am

fatmobile

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« Reply #16 on: February 21, 2006, 03:24:47 am »
Quote
That chip orientation (component side view) is standard practice over here, is it conventional to view designs solder side where you are from

 No I couldn't see the solder traces from the top so I drew it looking at the bottom.

Quote
I have shown electrolytics on my schematic and am guessing that C1 and C3 are electrolytics on the TD schematic.

 Other than that little green 3.3? cap, the rest are cylinder shaped.
 I'm not sure what constitutes electrolytic.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #17February 21, 2006, 09:59:27 am

regcheeseman

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« Reply #17 on: February 21, 2006, 09:59:27 am »
Image reworked to match gasser schematic.

Image removed due to error will post the correct one soon...

Quote from: "fatmobile"
Other than that little green 3.3? cap, the rest are cylinder shaped.
I'm not sure what constitutes electrolytic.


Normally cylindrical = eletrolytic but not always.

Electrolytics have polarity and are marked with a black band or similar to denote the negative terminal. Some are also marked with a '+' at the other terminal.

Reply #18February 23, 2006, 02:15:46 am

fatmobile

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« Reply #18 on: February 23, 2006, 02:15:46 am »
The round caps do have + and - on them.
 I'll get these printed up so I can get a better look at them.
Tornado red, '91 Golf 4 door,
with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #19February 23, 2006, 04:14:55 am

regcheeseman

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« Reply #19 on: February 23, 2006, 04:14:55 am »
Could you double check the values of the caps too? I'm gonna swap my components over soon...

Reply #20February 23, 2006, 10:43:37 pm

RabbitJockey

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« Reply #20 on: February 23, 2006, 10:43:37 pm »
could someone who does this do a write up on it, i'm considering it, i just need to get a gas tach, hopefully i can find an mk2 gas tach or a cabriolet tach. i hate westmoreland gauge clusters, they're like 20 times harder to read
98 Pontiac Grand Prix GT:stock daily
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81 Rabbit:AAZ, hybrid T3 turbo, Giles pump, lightened fw, and yellow clutchnet clutch.

Reply #21February 24, 2006, 04:16:28 am

johnny

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« Reply #21 on: February 24, 2006, 04:16:28 am »
I'm really interested in the tach conversion but I don't know anything about electronics.
The thing I do know is the gastach that's in my car is not a vdo but a motometer, a lot of vw's in europe have a motometer tach build in.

I hope you work it out first with the vdo tach. Is it possible I post a picture of my motometer tach so you can look for the differences.

Johnny

Reply #22February 27, 2006, 06:12:29 pm

MattRabbit

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« Reply #22 on: February 27, 2006, 06:12:29 pm »
As soon as someone gets one working, post up what needs to be altered on the gas tach to make it work with the W terminal.  I'm not too unfamiliar with a soldering iron to swap some components if need be. ;)

This seems like a very worthwhile project, keep it going!
'81 Rabbit Diesel
'01 Golf TDI
http://matt_lisa.home.sprynet.com/

Reply #23February 27, 2006, 09:28:23 pm

RabbitGTDguy

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« Reply #23 on: February 27, 2006, 09:28:23 pm »
I'd like to add the early (75-80) MK1 gasser tach to my 79's setup. Its not the westmoreland setup of course... they are the two individual "round" speedo and tach. I'm wondering what the conversion on this will be like...or if it is similar to the gasser tach mods above.

I have Roger Browns optical tach setup in my GTD but would prefer to make a clean stock looking install. Also wish I knew what that damm crank sensor on the TDI read for pulses and whether it is a digital or analog signal. I have the sensor on the motor...will still be there...how could I tell? Anyone know?

Joe
1979 Rabbit mTDI crazy $*(\%& bunny...
1972 VW Westfalia
2009 VW Tiguan SE 2.0T (Wife's car)
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Reply #24February 28, 2006, 06:07:04 am

regcheeseman

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« Reply #24 on: February 28, 2006, 06:07:04 am »
Quote
Also wish I knew what that damm crank sensor on the TDI read for pulses and whether it is a digital or analog signal. I have the sensor on the motor...will still be there...how could I tell? Anyone know?


It'll be conditioned as a digital signal and most probably be some for of proxistor (proximity sensor) using either a raised metal blip on the crank or a small hole drilled in the crank. It will measure absence or presence of metal.

The signal will pobably be low level analogue that is fed to an amp, the amp or tacho will then clean the signal up into digital pulses and then count the pulses.

Of course I am completely guessing here...

Reply #25February 28, 2006, 09:35:52 am

regcheeseman

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« Reply #25 on: February 28, 2006, 09:35:52 am »
First off, as a reminder, the standard gasser schematic...
images removed by reg.

A simplified diesel tacho schematic
images removed by reg.

Instructions also removed.


The fact that the board has unused spaces probably signifies it's application across a variety of applications

'Fatmobile', any chance you can check those cap values or are you pretty certain?

Just need to do the job and have a vehicle to fit it too...

Reply #26February 28, 2006, 12:48:28 pm

MattRabbit

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« Reply #26 on: February 28, 2006, 12:48:28 pm »
That's excellent.  As soon as someone tries this with success, I'll do the same.  What would the wattage rating be on the resistors?  1/2 watt?  1 watt?  These should all be parts that we can get at our local RadioShacks, correct?
'81 Rabbit Diesel
'01 Golf TDI
http://matt_lisa.home.sprynet.com/

Reply #27March 01, 2006, 06:41:04 am

regcheeseman

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« Reply #27 on: March 01, 2006, 06:41:04 am »
1/4 watt will be fine as there is very little power consumption. VW use 1/2 watts as standard.

Yes the bits should be readily available.

I will do mine today but will have to rig the altenator up to a spare battery and spin it with a drill or something to test it!

I'm still not sure how to calibrate the readout, I can simulate a W signal on the test bench and set it to a known freequency but I have conflicting advice on how many w terminal pulse equal 1 rev  :?  :?  :?

Reply #28March 03, 2006, 05:53:16 am

Mark(The Miser)UK

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« Reply #28 on: March 03, 2006, 05:53:16 am »
Quote from: "regcheeseman"

I will do mine today but will have to rig the altenator up to a spare battery and spin it with a drill or something to test it!

I'm still not sure how to calibrate the readout, I can simulate a W signal on the test bench and set it to a known freequency but I have conflicting advice on how many w terminal pulse equal 1 rev  :?  :?  :?


Reg
If you could find an Audi/Golf/Quantum Passat owner near you it would be easy to calibrate it against an existing tach... Now if you lived near Gloucester...
Mark-The-Miser-UK

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Reply #29March 03, 2006, 06:25:33 am

regcheeseman

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« Reply #29 on: March 03, 2006, 06:25:33 am »
Good thinking!

At this rate, I may try to buy a set of GTD clocks, take the schematic from them and use them to re-calibrate my A1 tacho and then sell them on.

Unless someone would like to lend me a set of clocks?  :D