[EDSanka]

The garage remote control rattling around in the door pocket of my Smart gave me a great excuse for a mod — hack the button bank to control the garage door.

After tracing the button bank connections with a DMM and a trip to Radio Shack, I have now converted a spare button in the bank to control my garage door.

Smart Car Garage Door Control - YouTube

Note: While this solution works for my USA version 2014 Smart ED, I have no idea how the button banks are wired in other models.

Here is the schematic. Electrically, it is rather simple. To the input terminals of a reed relay, connect the car's 12V supply and the switched ground from button #3 of the button bank. Then connect the output of the relay in parallel to the momentary switch of the garage remote control. That's really all there is to it.

Here are more detailed steps.
1. Dislodge the button bank from the dashboard, by sticking your fingers between the plastic housing of the bank and the dashboard until it snaps out.

2. Disconnect the wiring harness connected to the button bank.

3. Open up the bank housing by gently pushing the tabs on the periphery with a screwdriver.

4. Snip off the four white tabs in the back of button #3 (spare button). This is the third button from the left when viewed from the front. The lock button is the fourth button.

5. Close the button bank and put it away.

6. Remove the white housing around the connector of the wiring harness.

7. Crimp a connector pin to one end of a four foot wire and insert it into position #9 of the wiring harness connector. This is the green wire in the picture.

8. Reinstall the white connector housing.

9. Tap into the wire going to position #2 with another four foot long wire. You now have two wires. The wire from step 7 and the wire from this step.

10. Route the two wires under the dash to the driver side knee area, behind the OBD access port. The two wires will be connected to the input terminals of a reed relay. The location where the wires go doesn't matter. But the spot behind the OBD port acts as a nice tray to keep the garage door remote and the relay fastened.

11. Reconnect the wiring to the button bank and snap the bank back into the dashboard. We are now going to wire the relay and the garage door remote.

12. Follow the schematic and connect the output of the relay and the garage door remote. As the remote will have to be removed for changing battery every couple of years, it is better to not hardwire it, but use connectors instead.

13. Connect the input of the relay (the blue wires in the picture) to the wires from step 10.

14. Tidy up the excess wires. Tape down and velcro down the wires, remote control, and relay.

15. Sit in the garage, play with the button, and every time that garage door opens or closes, just admire the greatness that you are!

 

[Banana Jack]

Excellent thank you!

This is a great post. Thanks very much for sharing! I had been trying to do exactly this project but hadn't managed to complete it because I'd been following the instructions at Evilution but that article suggests connecting to pin 3 rather than pin 2. This gives a 12V output all the time except when the button is pressed, at which time it drops to 0V.

Using pin 2 as you have suggested is a much better way for me because the relay is then not constantly held open; instead, it operates only when the button is pressed so there's no battery drain when the button isn't being pressed and the remote isn't operated all the time if/when the vehicle battery goes flat or is disconnected.

For the relay, I used a TE Connectivity IM26TS (pdf) part code 3-1462039-2 which is really tiny and fits nicely inside the garage remote itself (I have a Silvelox door). The relay is needed because my remote uses a 3V lithium button cell and I didn't want to risk damaging it by connecting the remote to the 12V vehicle supply. I bought the relay from RS Components, stock number 515-527.

Thanks again for taking the time to share and include so many helpful hyperlinks and photos!

Best wishes from England,
Glenn

 

[EDSanka]

This is a great post. Thanks very much for sharing!

You are welcome! I was very happy with this hack and was really excited to share it as though I had just ended world hunger. But my post got no love for over two weeks until you found it useful. So thank you for soothing my bruised ego

I had been trying to do exactly this project but hadn't managed to complete it because I'd been following the instructions at Evilution but that article suggests connecting to pin 3 rather than pin 2.

What is the model of your car and what is the model of the car in Evilution's instructions? I wonder if wiring is different in different smart models. I couldn't find any official / unofficial wiring diagram of the button bank for my model, a US 2014 Electric. But it was easy enough to figure it out with a multimeter.

Using pin 2 as you have suggested is a much better way for me because the relay is then not constantly held open;

Actually, with my schematic, the relay output IS normally open, and closed only when the button is pressed. Am I misunderstanding what you are saying?

 

[MB DNA]

You are welcome! I was very happy with this hack and was really excited to share it as though I had just ended world hunger. But my post got no love for over two weeks until you found it useful. So thank you for soothing my bruised ego

:bigthumbup: GREAT MOD and write up! In my opinion, worthy of a sticky?

Sorry for the no love, bruised ego - probably a product of it being a little more than simple plug and play?

Got it on my "to do" list but will require a beer or two on ice for my after install party. Thanks for sharing . . . :cheers:

 

[Banana Jack]

How it works

But my post got no love for over two weeks until you found it useful. So thank you for soothing my bruised ego

Yes I was surprised no-one else had replied. The other main thread on this subject had received a lot of replies but it was from a few years ago and throughout the whole of that thread, no-one seemed to have figured out the exact wiring you did, where you really nailed it.

What is the model of your car and what is the model of the car in Evilution's instructions? I wonder if wiring is different in different smart models. I couldn't find any official / unofficial wiring diagram of the button bank for my model, a US 2014 Electric. But it was easy enough to figure it out with a multimeter.

I have a UK 2014 Electric Drive. Evilution's instructions are for the 451 generally. His pictures and diagrams are great, but the text is a little vague (no offence if you're reading, Evilution!). I suspect that the ED is no different to a standard 451 in its button bank wiring. I couldn't find a schematic either, apart from Evilution's which wasn't complete. I was a bit reluctant to start prodding around with a multimeter for fear of frying the computer; those pins are very close together.

Actually, with my schematic, the relay output IS normally open, and closed only when the button is pressed. Am I misunderstanding what you are saying?

Sorry, I probably wasn't clear enough. I should have said, "Using pin 2 as you have suggested is a much better way for me because the relay is then not constantly held closed". You understand correctly though. Essentially, the button output (pin 9 for button 2 in your instructions) is normally held at 12V but it drops to 0V when the button is pressed. Connecting this to one side of a relay coil and connecting the other side to constant 0V (pin 3 on Evilution's instructions) means that the relay sees a voltage (potential difference) of 12V when the button isn't being pressed, and 0V when it is. This is kind of the opposite of what you usually want, because you don't want the relay coil drawing current under normal circumstances otherwise it could eventually flatten the car battery. My workaround was going to be to use a relay with NC (normally closed) contacts, but still the problem of long-term battery drain would have remained.

Your method connects the relay to pin 2 (12V) instead of pin 3 (0V) and so the relay sees a voltage of 0V under normal circumstances (since both sides of the coil are at 12V) and then when the button is pressed, it sees 12V (because the button side drops to 0V). This is totally what you want! When the button isn't being pressed, no current is drawn and the relay isn't activated. When you press the button, the relay sees a momentary 12V whilst you keep the button pressed. The coil activates and effectively presses the garage remote button. Then when you release the button, the coil deactivates and the garage remote button is released. Perfect!

 

[Evilution]

For future post clarity I'd like to point out that my page on this was only covering negative switching because that's what most of the standard switched ancillaries use on the smart.

There is 1 live wire coming from the SAM unit, when the button is pressed it momentarily earths it which switches a transistor in the SAM unit, flips a relay and powers what ever it is.

I suspect the page seems vague because it didn't really cover your application.
You were using pin 9 as an output, I was using it as an input.

I do have a circuit diagram for converting a momentary button press to a latched voltage supply so I will add this at some point to help people who need to latch a positive supply.
When I get a chance I will add momentary positive switching info to this page too. I just need to find one of my spare button banks and have time to go over it.

 

[Banana Jack]

Thanks Evilution, that's great to have clarification. And the latched circuit diagram sounds interesting too. I expect that might be useful for certain other applications like an extra light.

 

[Marco Stefanelli]

Hello to everyone.

I'm Italian so I apologize in advance for all the errors

I did the same mod but my garage has two doors so I used two buttons instead one.

I had a problem because i noticed that pin n.9 has 8v voltage when it's not in work so I can clearly hear a buzz from it if I'm gonna plug the circuit.. it's not enough for close the contact.

Do you have the same problem?

Thanks Marco.

 

[EDSanka]

Ciao Marco! I wish I could write in italiano as well as you write in English.

The original mod I posted has worked without any flaw for the past three months. No buzzing. Unfortunately, I didn't save the piece of paper where I wrote down the measured voltages of all the pins on the connector. But I don't think I read any 8V pin.

 

[Marco Stefanelli]

It's strange, but at least I could use the 13th and 14th pins for the mod, on them I can't read more than 1v.

Btw after that I disconnected the circuit from the 3th button (pin 9) and when I tried to misure V between it and + for check again and here we go white smoke from the board..

So I'checked all the car command and everything worked fine..

Keeping my tester away I remounted the bank button, and I pushed the evil 3th button just for be sure and it smoked again...

After that I unassembled again the bank button looking for a short circuit between n.9 and + but nothing.. everything was fine, so I unsoldered the little cable from pin 9 and I saw that the short circuit destroyed just the upper button no resistors were damaged.

After replacing all I tried again the button and nothing happens.. So it fine for me.. but I don't really know why it did so.

Anyway have you never studied Italian?

I'll have my American trip on september

 

[mcowher]

Sorry for the necro-post, but does anyone still have the images that EDSanka took when he did this mod? They are all gone from the Amazon clouddrive.