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Wiring Up Extra Gadgetry... Any wiring experts out there?
The Great Fandango - 17/9/07 at 09:52 AM

You're going to think I'm slightly strange for wanting all the following working simultaneously : -

1. Digidash II

2. 'Shift-I' shifter-lights

3. Acumen DG8 Gear Indicator

(especially as the Digidash does in fact have shift-light and gear display functionalities).

The fact is the Digidash is difficult to see when on track and you want things in your line of site. With this in mind I've mounted the DG8 and Shift-I on the underside of the aeroscreen just where my line of vision is.

Question 1:
As all three 'gadgets' require an rpm input my initial thoughts were to simply split/branch the yellow rpm wire to all three in parallel. Unfortunately I have noticed I now only get intermittent readings of rpm. I figured this is probably due to me being a numpty and the fact you simply can't split the signal like that?

Question 2:
The Acumen DG8 gear selector needs a speed sensor input. I had a look inside the wire from the Digidash's speed sensor cable but it's a tad on the complicated side and in any case the guys at ETB Instruments reckon it'll screw up the speed reading on the Digidash (kind'a in the same way that I've screwed up my rpm readings). Is there a simple speed sensor kit I can buy which I'll mount on the prop next to the original speed sensor?

Does anyone on this forum run more than one speed sensor for different applications?

Any help greatly appreciated.

The car's running now, it would be nice to get to the next trackday and actually make the most of the day.

Best regards


Kyle, Leeds

[Edited on 17/9/07 by The Great Fandango]

02GF74 - 17/9/07 at 10:57 AM

quote:
Originally posted by The Great Fandango
Question 1:
As all three 'gadgets' require an rpm input my initial thoughts were to simply split/branch the yellow rpm wire to all three in parallel. Unfortunately I have noticed I now only get intermittent readings of rpm. I figured this is probably due to me being a numpty and the fact you simply can't split the signal like that?


Without knoing the characteristics of the signal and the input stages to the the instruments, is is quite hard to make any suggestions.

What you have attempted, assuming it is wired up correctly, is not unreasonable, as for example you can purchase Y-pieces that allow two headphones to be used from one socket.

The problems you are experiencing may be that one or more input stages are conditioning the signal so it is not longer of the type another input satge expects e.g. one of them has a smoothing capacitor.

Or it would be the input stages present a load so that the amplitude of the signal diminishes again with similar results.

If your signal is two level e.g could be 0-5v or 0-12 V then you could use a simple buffer stage for each input.

If analogue, then more complicated and would need an amplifier of some sort.

BenB - 17/9/07 at 11:04 AM

It really depends on the strength of the signal. If the RPM signal is full voltage (ie 12v) straight off the ECU you could try splitting it into the three signals but putting diodes in each branch to stop the signals getting confused. It sounds like the input stage of the various bits of kit are confusing each other.... Otherwise as mentioned a simple op-amp buffer stage would work- only problem there would be you'ld need a rail-to-rail op-amp because the signal will likely be at the same voltage as the op-amp power supply.

The Great Fandango - 17/9/07 at 11:42 AM

He scratches his head...

Can you point me in the general direction of a suitable "rail-to-rail op-amp" please?

:0)

Hellfire - 17/9/07 at 12:22 PM

Wouldn't it be far simpler to move your digidash into your line of sight? Then you'de have no need to muck about duplicating what the DD already tells you.

Steve

The Great Fandango - 17/9/07 at 12:38 PM

Hellfire,

I can see your point but

- I already had the 'Shift-I' and Acumen DG8 sitting in the garage doing nothing (had planned to put them into my Westfield last year)

- I've done all the hard work with regards to positioning and wiring (and it looks pretty damn good too). The DG8 in particular is one funky piece of kit.

- The Digidash is mounted flush to the dash so it would need a whole new dash

- In my opinion the Digidash is still a complex thing to look at on the track

- I prefer to use the DigiDash to display speed, oil pressure and water temp. I'd have to keep pressing its buttons to then get the gear data

[Edited on 17/9/07 by The Great Fandango]

gingerprince - 17/9/07 at 12:39 PM

Where are the DD and Acumen grounded? If they don't share the same ground (i.e. they are grounded to different points of the chassis) you could get a ground loop and therefore interference between the 2 devices.

Might make no difference at all, but if you haven't grounded them both to exactly the same place it's a quick and simple check before trying more complicated solutions.

The Great Fandango - 17/9/07 at 12:50 PM

Pretty much everything in the car earths back at a huge clump of wiring on a block.

In the case of the 'Shift-I' and Acumen DG8 I simply ran a black coloured wire across from the block and soldered both gadgets to a common point on this wire just beneath the scuttle.