Disco 2 Electrical guru please?

Is there any way to detect when a Disco 2 manual is travelling slow enough to engage difflock? (<40mph)

I was thinking of a project to have difflock engaged by an air cylinder and a switch in the cabin. The trouble is, I can't afford to accidentally engage the difflock when travelling at higher speeds.
If there's a way to detect low speed then I can interlock the switch until the speed is acceptable to lock the diff?

Air activation of the diff lock mech has been discussed and done a few times.

As for fitting a safety interlock regarding speed, I have never heard of this, Maybe a switch out of the way with a separate override switch to avoid accidental engagement may be a better option.

Cheers

"Is there any way to detect when a Disco 2 manual is travelling slow enough to engage difflock? (<40mph)"

A working speedometer will be useful, so yes.

It was just that I thought to place the switch next to the window controls but that location is a bit exposed to water bottles, stray hands, dog paws etc.
If I place it on the dash out of the way, it would not be so easy to engage going over rough ground.

Of course, it would be easier just to get the mechanical linkage but it would be cool to be air operated.

Why not interlink it to low range? That will preclude it ever doing 40mph....

Thanks for your input Discool, but I'm trying to prevent the switch being activated by accident when travelling on the road at speed.

chris-the-gerbil said:

Why not interlink it to low range? That will preclude it ever doing 40mph....

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That's not a bad idea. I could fit a micro switch on the low range position.

Would it be possible to attach a Bluetooth OBD2 device and hook that into an Arduino/ Raspberry Pi, which could detect speed via ECU?

Never tried this but would think the only way to detect speed electronically would be via the ECU.

You can certainly hook arduino and raspberry up to a solenoid for your air device, a solenoid costs about £5 direct from China. An ESP8266 Thing is under a £10, iirc this has Bluetooth.

Then a piece of code to interrogate the ECU if the switch is positive, when speed is under 40mph apply power to the solenoid.

If you went this route I would probably err on the side of caution and set the speed to <30mph.

Alternatively get a GPS enabled device to detect speed, again GPS is easily connected to Arduino, raspberry or ESP8266 Thing, all these devices operate on 5V or 3.3V DC depending on which model is used.

I would of thought that would work, no guarantees though.

Alpinejim said:

Thanks for your input Discool, but I'm trying to prevent the switch being activated by accident when travelling on the road at speed.

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It my belief that the system would have push button switches to switch a relay to operate the pump or any other kit required my opinion is u would have to be very clumsy to accidentally press one of them at speed, but if you believe it could happen there are switches with protection covers and if that's not what you want then fit a key operated master switch on the 12v feed into the control unit, and if u require illuminating lamps to give a status indication of the switch positions that's easy to do also. It's all very simples.

Rather than trying to build some kind of speed interlock, maybe you'd be better off with a toggle switch and what's called a "missile cover" which would mean you'd have to physically lift the cover to operate the switch, hence preventing accidental operation.
The type of switch I've shown is an "On-On" type which could be wired to say, push down to engage and up to dis-engage the diff lock.

http://www.ebay.co.uk/itm/ON-ON-Toggle-Flick-Switch-12V-Car-Dash-Light-SPDT-10A-Water-Missile-Cover/371768202525?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D2%26asc%3D20140122125356%26meid%3D1cff530adce545479d68b70e9d2db733%26pid%3D100005%26rk%3D4%26rkt%3D6%26sd%3D252246909694&_trksid=p2047675.c100005.m1851

Alpinejim said:

Is there any way to detect when a Disco 2 manual is travelling slow enough to engage difflock? (<40mph)

I was thinking of a project to have difflock engaged by an air cylinder and a switch in the cabin. The trouble is, I can't afford to accidentally engage the difflock when travelling at higher speeds.
If there's a way to detect low speed then I can interlock the switch until the speed is acceptable to lock the diff?

Click to expand...

You could take a tap from the transducer to get the speed signal pulse, run that via a logic unit made from an arduino for example, it can simple be programmed such as this:

If pulse<2000
Set Relay = 1
Otherwise
Set Relay = 0

You would need to code the logic unit to know what Pulse and Relay was but the code would be about 6-10 lines!

You would need to ascertain the pulse rate at 40mph.

The next issue is that difflock won't always engage depending where the gears sit, so you would lose the "feel" of the stick to work out when it is going or not.

Thanks for all of the options everyone.

I think the Pi interrogating the ECU is way more complex than I need - although I admit that having an air op diff is more complex than necessary anyway. However, if you could do this, you could easily have an auto locking diff if the ECU can tell you which wheels are losing traction.

The desire for in interlock in the first place was really due to the placement of the switch which would be on the centre console between the window switches. This is easy to get to without leaning but also very easy to switch the difflock instead of the window.
The missile cover would solve that I suppose. But, how long until that gets broken?

I like the lo range interlock option so far.

Alpinejim said:

But, how long until that gets broken?

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They survived in the Tornado's quite well so should be fine in a Landy!

Alpinejim said:

That's not a bad idea. I could fit a micro switch on the low range position.

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but you wont have diff lock in high range
I understand dog paws my dog keeps putting windows up down and also S mode on my transmission ..but like neily said ad in an isolator switch this can placed any where with a indication lamp to say its armed
you have plenty of options ....if this was me I would install a gear knob from a hilux instead of a micro switch

discomania said:

They survived in the Tornado's quite well so should be fine in a Landy!

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Yes, but they weren't made in China!

discomania said:

You could take a tap from the transducer to get the speed signal pulse,

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This thread being about a Disco 2 i eally doubt that cos it doesnt have a transducer... the VSS is delivered by the SLABS ECU

Sierrafery said:

This thread being about a Disco 2 I really doubt that because it doesn't have a transducer... the VSS is delivered by the SLABS ECU

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So it is! I neglected to remember that! Not a problem thought.

You can take a feed from the wire on pin 13 of the black plug from the ECM which delivers a PWM signal (0-12V) to the speedo.

Frankly, I don't see the need for trying to decode a Pulse Width Modulated (PWM) signal to determine vehicle speed. Almost every other owner of a Disco fitted with diff lock seem to be satisfied with the Hi/Lo gear lever.
Why not just fit a switch system to the lever?
I'm all for KISS.

brian47 said:

Frankly, I don't see the need for trying to decode a Pulse Width Modulated (PWM) signal to determine vehicle speed. Almost every other owner of a Disco fitted with diff lock seem to be satisfied with the Hi/Lo gear lever.
Why not just fit a switch system to the lever?
I'm all for KISS.

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So am I, personally I think it is a pointless exercise in as much as it is really not difficult to nudge the shifter over to the side for diff and it is a mechnical system that in theory should be very robust in use and cannot be "accidentally" deployed at the flick of a switch.

I had a RR transfer case with electric hi-lo and a VCU, someone installed this into their 90 so they had "automatic" diff lock and electric hi-lo - that is pretty good although you then need to rely on the VCU being reliable.

A PWM signal is however very simple to read and takes no decoding as such, it is simply a pulse, count the pulses and the software knows what to do.

discomania said:

So it is! I neglected to remember that! Not a problem thought.

You can take a feed from the wire on pin 13 of the black plug from the ECM which delivers a PWM signal (0-12V) to the speedo.

Click to expand...

I know that and i know you knew that i just corrected to not let somebody think that the D2's VSS is coming from a mechanical transducer