Emerald Map Switching/switch install question

[Smitters]

I have an Emerald K6 with three maps loaded - a higher RPM full power map, a dropped rev limit "wet weather" map and a security map that prevents the car running. This was all controlled by a rotary switch that's gone on the blink. The ECU has presumably defaulted to the 5 volts map, which annoyingly, seems to be the security map, making the car a big paperweight!

My question is, can I replace the rotary switch with a three position toggle, which would be more in keeping with the dash anyway? The question will outline the limits of my electrical knowledge nicely I think...

Many thanks in advance.

[GreenV8S]

Smitters said:

can I replace the rotary switch with a three position toggle

I can't tell you whether you're capable of doing it, but it ought to be straight forward for a competent electrician.

You would need to discover the electrical properties of the existing rotary switch, find a toggle switch with the same electrical characteristics which fits your packaging requirements, and transfer the wiring to the new switch.

[Smitters]

GreenV8S said:

Smitters said:

can I replace the rotary switch with a three position toggle

I can't tell you whether you're capable of doing it, but it ought to be straight forward for a competent electrician.

You would need to discover the electrical properties of the existing rotary switch, find a toggle switch with the same electrical characteristics which fits your packaging requirements, and transfer the wiring to the new switch.

OK - thanks - in principle then I can have a bash. I didn't install the rotary switch, so I'll have to reply on part numbers and google a bit, or failing that, as you say, a friendly auto-electrician. It's winter at least, so there's some learning time available.

If anyone's actually installed such a switch, any pointers to good switchgear would be gratefully received.

[CrutyRammers]

Give emerald a ring or email - very helpful folks.
IIRC the manual specifies a rotary switch but they'll be able to tell you for sure.

[anonymous-user]

I'm going to assume that the input to the ecu used for the mode switch is an analogue one. ie it is presented with a voltage, in the range of (usually) 0 to 5v, and depending what that voltage is, the ecu swaps between maps.

So, if this is the case (and it is likely to be so) the rotary switch will be in the form of a "potential" divider. ie, it will uses fixed resistors, of different values in each switch detent position, to modify the voltage sent to the ecu input as the rotary switch is operated.

The main question is where is the "Pull up" resistor. Two options exist:

1) The rotary switch has 3 wires going to it; they are 5v, 0v, and signal. The switch acts to ratiometrically return a fixed proportion of the 5v supply. For example, if the switch had two 10k resistors across it in one position, the returned signal voltage would be 2.5v (because the top 10k resistor (connected to 5v) and the bottom 10k resistor (connected to 0v) form an equal potential divider)

2) The rotary switch only has 2 wires going to it; In this case, the pull up resistor is in the ecu, and the switch will only have the pull down resistors connected to each switch position. For example, imagine there was a 10k pull up to 5v in the ecu, then if the switch connects another 10k resistor between 0v and that output, the resulting voltage is once again 2.5v.



So, if you can, look at the switch you currently have and identify how many wires it has leading to it. If you have a multimeter with a resistance measurement mode, you can measure the resisitance between those wired (when unconnected from the ecu). A photo of said switch is also worth 1000 words btw ;-)


Some good basic learning info here: potentiometers

[Smitters]

Thank you MaxTorque.

I'm away from the car, so a photo isn't going to be forthcoming, but I shall do some reading. From a quick review though, it sounds like the switch I have is "smarter" than off, a bit on, on in terms of the voltage it's showing to the ECU, in the sense it has to create the 2.5V input to activate a third map.

[Penelope Stoppedit]

Here you go, As max has already mentioned, things may not be as simple as how they look


3-way Dashboard switch prewired with ECU aux port plug


Quality 3-way Dashboard switch with knob, prewired with ECU aux port plug and resistor. Allows easy

and convenient ECU map switching. Compatible with Emerald K3 and K6 ECU's.

Availability: In stock
Excl. Tax: £15.00 Incl. Tax: £18.00

http://www.emeraldm3d.com/3-way-dashboard-switch-k...

[Ive]

there is an internal pull-up resistor.
the switch, rotary or toggle, does nothing else than creating a voltage divider between the internal pull up resistor and ground.
It does so by directly connecting the input pin to ground to select 0V for map1,
It connects a 1 kOhm resistor between ground and the input pin to select 2.5V for map2
it opens the the connection (connect nothing) to select 5V for map3.

[GreenV8S]

Ive said:

there is an internal pull-up resistor.
the switch, rotary or toggle, does nothing else than creating a voltage divider between the internal pull up resistor and ground.
It does so by directly connecting the input pin to ground to select 0V for map1,
It connects a 1 kOhm resistor between ground and the input pin to select 2.5V for map2
it opens the the connection (connect nothing) to select 5V for map3.

In that case it should be a doddle to wire up a three position toggle switch in place of the rotary switch.

[anonymous-user]

Ok, so it's really a 2 wire type arrangement, but it uses 3 wires so the resistors can be hidden in the dsub connector cover, or soldered to the back of the rotary switch.

So, all you need to confirm, is what value is the resistor to get half voltage. Suggestion is that it is 1k

So, you buy a 3 way ON-OFF-ON latching toggle switch, ideally something with a "lift to move" type lever to prevent accidental mis-selection ie:



You connect the common (centre) terminal to the ecu signal wire, you connect one of the other terminals to the 0v wire out of the ecu, and you connect a 1k (assuming it is 1k) resistor between the top terminal and the bottom terminal.

So:

When the switch is UP, the ecu sees 0v, as the singal wire is connected (pulled down) directly to 0v

When the switch is in the MIDDLE, the ecu sees 5v, as there is nothing connected to the signal wire.

When the switch is DOWN, the ecu sees 2.5v, as the signal wire is connected to 0v via the 1k resistor



You can also get switches that are OFF-ON-ON, if you want the 5V position to be one end of the travel etc

Edited by anonymous-user on Friday 10th November 18:19

[GreenV8S]

The problems with the existing switch might be cause by a simple electrical break in the wiring or ECU connector rather than a fault in the switch itself. In that case it should be pretty easy to repair.

[Smitters]

Awesome info. I'm quite tempted just to buy another Emerald rotary switch, since that's what's apparently installed. I'd been trawling various kit builder sites looking for such a thing without realising it came from Emerald in the first place! That said, I'd much prefer a toggle, so will have a read of all the info and a ponder.

[anonymous-user]

RotarySwitch


Spend the extra cash on beer!

[GreenV8S]

Smitters said:

Awesome info. I'm quite tempted just to buy another Emerald rotary switch, since that's what's apparently installed.

Suggest you take the existing switch off and see what's wrong with it before you decide. If it's a simple wiring fault, which seems likely, that ought to be a five minute fix which will save you time and money buying a new assembly.

[Krikkit]

Smitters said:

Awesome info. I'm quite tempted just to buy another Emerald rotary switch, since that's what's apparently installed. I'd been trawling various kit builder sites looking for such a thing without realising it came from Emerald in the first place! That said, I'd much prefer a toggle, so will have a read of all the info and a ponder.

In which case I'd pull it off the dash and get a multimeter on it, shouldn't be hard at all to sort out what it's doing.