I'm working on a project for my car. In it's stock form, my car came with a deployable spoiler. I replaced it with a fixed spoiler. With the deployable spoiler, the chassis ECU sends 12VDC to the motor, but the polarity of that signal is controlled by two microswitches in the mechanism. If the ECU sees that the stowed microswitch is closed, it sends 12VDC +/-. It then waits until the deployed microswitch closes to stop the voltage to the motor. Conversely, when it sees the deployed microswitch closed, it sends 12VDC -/+ (opposite polarity) to the motor until the stowed microswitch closes.

I need to emulate this or the car's performance is degraded significantly. There is a fixed spoiler option when you buy the car, and when that option is selected, the car comes with a little box that replaces the actuator motor and emulates this function. Unfortunately, that little box costs almost $600. I think I can emulate this with a couple relays and a latching relay, but I was hoping there was a latching relay out there that used voltage polarity to latch rather than a set/reset. Has anyone seen a latching relay like this? Anyone have any suggestions? Thank you.

Here is the wiring diagram of the spoiler:

 

This Relay works that way.

I need to emulate this or the car's performance is degraded significantly.

Why is that?

 

Wow, thanks so much. I will look at that closely.

The reason it limits power if you simply pull the plug on the actuator is because the car doesn't produce enough downforce, apparently, above 70mph for the rear to remain "grippy" without the deployable spoiler. The fixed spoiler option for the car is quote pronounced, and most like the looks of the car without it, so they made the deployable spoiler hidden unless you are going over 70mph. It's a Jaguar F-Type coupe. The spoiler is the little flap in the center behind the rear window that is quite ugly when deployed, but I didn't want to simply disable it for safety reasons, so I installed a more aesthetically pleasing fixed spoiler instead. My spoiler is exactly like the Jaguar SVR spoiler, except it doesn't move.

 

I think I can emulate this with a couple relays and a latching relay,

Curious to see this circuit.
Might be possible using only one SPDT relay and the latching relay.

 

The existing circuit is above. I'm trying to emulate the actuator on the left side of the schematic.

 

Do you have a circuit?
I have a couple of designs available.

 

The existing circuit is above. I'm trying to emulate the actuator on the left side of the schematic.

Version #1 suggestion:
Circuit shown in the standby state.
When the car is above 70mph the ECU will see the NC position of the RL2 contact and apply power to latching relay RL1.
Relay RL1 closes and applies power to the timing circuits of Q1 and Q2.
Q1 will activate RL2 quickly (via the timing circuit of C1, R3 and D2) simulating that the spoiler is raising.
Two seconds later Q2 will activate RL3 (via timing circuit of C2 and R5) closing its contacts simulating that the spoiler is fully raised and turning OFF the voltage to RL1.
When the vehicle has slowed to 50mph the ECU will send a reversed polarity voltage to reset RL1.
C2 will discharge quickly (via R4,D4, and R6) and RL3 will drop out simulating that the spoiler is lowering.
Two seconds later C1 will have discharged (via R1 and R2) low enough that RL2 will drop out reclosing its contacts simulating that the spoiler is fully down.
Resistor values for R2-R3 and R5-R6 are estimates only. Will depend on the actual relays used for RL2 and RL3.

 

Version #2:
This circuit should work if the ECU is not fully monitoring the micro switches.
Meaning it's looking for a close contact in order to apply power to RL1 and doesn't care if the contact remains closed during the timing cycles for both raising and closing emulations.
This version provides a two second delay before RL2 contacts close simulating that the spoiler is fully raised.
Followed by another two second delay before RL2 drops out when RL1 resets.

 

If you always have a spoiler "deployed" couldn't you just short the spoiler raised switch contacts?

 

I think the ECU is only looking to see a raised spoiler above 70mph.

 

Yes, it raises the spoiler only when above 70 MPH (might be 75, I'm not 100% sure).

 

Looking at your circuits, I have a question. It looks like it requires a separate 12V power supply. There is no power supply except for the motor circuit. How would I supply 12V to the RL2 or RL3? Use the motor supply?

 

12 volts from the car battery.
Anyplace you can tapped into
Has to be 12 volts continous
Only need maybe a 100ma of current depending on the relay or relays used.
Using the motor supply but with a different circuit is viable.

 

Yeah, unfortunately there's no really good way to run an extra 12V up to where the emulator would be. Here is a photo of what jaguar uses, and as you can see, it simply plugs in place of the actuator- there are no extra power wires. The actuator has the same plug on it as this emulator does, and you simply unplug the actuator and plug in this device. I want an emulator that is just like this one, only not $700.

 

I have a circuit for that, can post later today.

 

Awesome! Thanks.

 

Possible solution using two latching relays.

 

Excellent. Thanks so much.

 

I just purchased all of the parts. I'll put it together on a prototype board and let you know how it works. Thanks!!

 

I just purchased all of the parts. I'll put it together on a prototype board and let you know how it works. Thanks!!

If it doesn't work as seen in post#17 the same parts will still be required using a different circuit.
Nothing will be wasted.