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Discussion Starter #1
Have you ever wanted to use a spare switch in the button bank to power a 12 volt circuit? The switches in the button bank are intermittent and in order to avoid programming the SAM to convert a switch to a true on/off circuit all you have to do is patch in a latchable relay. See this link to ebay. Hot 12V 1 Channel Latching Relay Module with Touch Bistable Switch MCU Control | eBay The evilution site describes how to disassemble the button bank and provides a wiring diagram for the button bank. I used one of these relays to power a wind up key on my wife's Smart. Smart simply paints the button bank black, so using my Dremel I was able to scratch/slightly grind the paint off the switch to make the windup key icon. Now the factory LED light in he switch lights up the icon! Here's a link to my youtube video of the windup key. The video also shows the button bank in use.
The next circuit I'm going to power on my Smart is a pair of Angel Eyes and the fog lights. Enjoy!
 

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Have you ever wanted to use a spare switch in the button bank to power a 12 volt circuit? The switches in the button bank are intermittent and in order to avoid programming the SAM to convert a switch to a true on/off circuit all you have to do is patch in a latchable relay. See this link to ebay. Hot 12V 1 Channel Latching Relay Module with Touch Bistable Switch MCU Control | eBay The evilution site describes how to disassemble the button bank and provides a wiring diagram for the button bank. I used one of these relays to power a wind up key on my wife's Smart. Smart simply paints the button bank black, so using my Dremel I was able to scratch/slightly grind the paint off the switch to make the windup key icon. Now the factory LED light in he switch lights up the icon! Here's a link to my youtube video of the windup key. The video also shows the button bank in use. A "Hybrid" Smart car in Alaska! - YouTube The next circuit I'm going to power on my Smart is a pair of Angel Eyes and the fog lights. Enjoy!
That was a great job on the wind up key. It must have been really tedious to etch a key icon like that on a small bank button. You must have patients,steady hand, and artistic ability, I have none of that. But you really piqued my interest. Could you elaborate a little more on modifying the button bank? I like many other don't have a subscription to the wonderful Evilution site. Do you have to disconnect a pair of wires from the button bank connector to keep from tripping the SAM up? I'd like to do the garage door opener mod with the button bank and that could be momentary, so no need for a latching relay, but I do have a couple of other installed projects that I could lose the existing switch and route it through the button bank and a latching relay. DCO
 

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There are tabs on the 4 corners of the button that keep it so you can't push it to activate the switch. remove the tabs and the button will work . as for the wiring, you can add a wire on the connector in the correct spot and you are good to go.
Remember, the buttons when pushed, provide a ground so you will most likely need a relay to convert to a power source. The switch won't take much current before melting so a relay is a good idea anyhow.
 

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Discussion Starter #4
I first decided which button to use. Then disassemble the button bank and cut off the 4 tabs on the back of the button so you'll be able to make that button/switch useable. Then you need to determine which two wires in the wiring harness connect to that button/switch. That wiring diagram is also on the Evilution site. (Although it might be in other locations too. If it's not out there I can try and figure out how to post the diagram.) Cut the two wires that go to that button/switch. Put electricians tape on the two wires that go into the harness. This will insolate the circuit you're 'switching' so you don't have any conflicts with the SAM. Now, use the wiring diagram that comes with the latching relay and you'll have a properly working on/off switch! Now, etching the wind-up key icon wasn't that difficult, it just took some time. I searched the web for switch icons. I found one close to a wind up key and printed it out and just modified it a bit so it looked more like a wind-up key. I then taped my icon over the button/switch and poked the outline of the icon through the paper with a pin. I removed my paper template, then used my dremel with a very small burr cutter and used it to 'scratch' the paint off the face of the button. And yes, it does take a steady hand. :)
 

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Thank you Limoak for posting this. I was afraid to do any button bank mods for fear of making problems for the SAM (didn't know if SAM monitored all the switches even though they all aren't used). When I do mods to my Smart I always try to keep as much hidden as possible so in that regard I have added 4 switches to my smart. One turns on my foglights that I added (rocker switch under the dash), one turns on my DRL's (rocker switch by turn signal lever), the other turns on my power inverter that runs my stereo system (toggle switch under the dash) and the last one came with my kit for my heated seats (knob switches on center console). The heated seat switch I can't mod out to the bank because it is a 5 position switch, but the others are a definite canidate to integrate into the bank.



Out of the six buttons that are a candidate for modding, everyone I guess has #5 used for the TMPS. So that leaves 5. I have never seen #3 used on any vehicle that I can find. 1,2,4,and 6 when used from the factory have an LED that lights when that particular function is used, so I don't know if that factor plays into our purpose of using the button for a different purpose. I realize we take the button out of the circuit when we cut the wires to the harness, but if there are a function LED connected to the unused buttons that might affect the use of the button for other purposes. I will have to disassemble mine and see. If each micro switch in each button is indeed just a momentary switch then the Sam must do the actual switching for that circuit. I say that because the heated seats have high and low, so a momentary push would
select high and another momentary push would select low with the SAM doing the actual switching. DCO
 

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Discussion Starter #6
DreamCarOwner- I don't know, even if a particular switch is not used, if the SAM 'monitors' that unused switch/circuit or not, but by cutting the wires that go to the SAM from that unused switch/circuit, the switch is obviously disconnected from the SAM. (Better safe than sorry, right?) I think the LED's that are in the switches come on when the car ignition is on. You simply don't see the light from the LED cause Smart painted the surface of the switch black. So, it was a pleasant surprise to me that the switch LED shows through! (Now I might be wrong on this, so if you find that having power go through the particular switch/circuit powers the switch LED, instead of the car ignition, please post your findings. (Either way, the LED should light.) Each switch in the button bank is a momentary switch and yes, from what I understand, the SAM does the actual switching for each circuit. That's why you have to add a latchable relay into each circuit. (And as others have stated, the switch can't take a lot of amps either.) One more note- Before I stuffed/zip tied the latchable relay under my dashboard, I put hot glue over the back of the printed circuit board of the relay to eliminate the chance that the back of the relay would come into contact with any metal and ground it out. Thought you'd like to see a close up picture of my button bank. Post any questions if you need help.
 

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Nice job! I activated my fog lights on this button (the standard button for factory fogs). I drilled a hole for the green "ON" indicator to show through, and then filled in this new hole with clear hot-glue. I have not attempted to etch an icon on the button for fear of messing it up. Thanks for the tips. How deep did you need to grind into the button to remove the black coating?

One note of caution re this button bank. This type of contact uses a conductive coating on a flexible membrane to bridge the switch contacts on the circuit board - the same design as your common TV remote control. These switches are not designed to take much current, likely in the microamp to several milliamps tops. A relay generates an inductive kick from the coil when deactivated, which will erode this conductive coating. A diode across the coil will reduce the magnitude of this kick, but is still much more than the switch is designed for. I'd suggest using a transistor or other device to activate your relay.

~toaster
 

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Discussion Starter #8
Toaster- thanks for the idea of drilling a hole in the switch for the "on" light. I like your idea of the hot glue "window". Since the switches are merely painted black, you barely have to scratch the paint off. It might be the thickness of printer paper. Thanks for the caution on the transistor/relay warning. I'm not much of an electronics wizard, do you have any specific recommendations on how I should do what you're recommending?
 

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Toaster- thanks for the idea of drilling a hole in the switch for the "on" light. I like your idea of the hot glue "window". Since the switches are merely painted black, you barely have to scratch the paint off. It might be the thickness of printer paper. Thanks for the caution on the transistor/relay warning. I'm not much of an electronics wizard, do you have any specific recommendations on how I should do what you're recommending?
Limoak, sorry I missed the fact that you are using a module for this purpose, not just a simple relay. Your module provides both the relay driver and flyback diode on the board, so you should be just fine.
:)

I am shocked that the manufacturer of your module used a microcontroller to do such a simple function which could have been implemented with a single flip-flop!
:eek:

~toaster
 

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Discussion Starter #10
Toaster- I wish I understood what a fly back diode does, but thanks for the re-assurance that I'm good on what I've got. I'm glad I bought several of hose modules!
 

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Toaster- I wish I understood what a fly back diode does, but thanks for the re-assurance that I'm good on what I've got. I'm glad I bought several of hose modules!
The flyback diode shunts the voltage spike that is generated when the relay is turned off back through the relay coil windings so the electrons run around in circles in the relay coil windings until they get dizzy, fall down and die.
 

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Limoak I just ordered 3 of the latching relays you recommended from ebay. I have a rocker switch for my foglights under my dash so I hope to convert it to the button bank. The foglights are COB LED's so the draw should be way below the 10 amp rating of the relay.
The second switch I hope to do away with is the surface mounted rocker switch I use for my DRL lights which are also LED and very low current draw.
The third conversion will be to get rid of a toggle switch under the dash that provides 12 volt power to a 200 watt power inverter which powers my Altec Lansing sound system. Now at full draw the inverter should pull about 15 amps, but I never play the system anywhere near full volume, so if I'm careful I should be able to pull it off and hopefully stay below the 10 amp rating of the relay.Maybe I'll put a 10 amp fuse inline just to be safe. If it doens't hold the current and I accidently blow the relay, I'll just order another and use the latching relay to trigger another 25 amp relay I have left over from my heated seats project.
Now I guess I need to look for switch icons that I can pin the outline as you suggested and then use the Dremel. I presume you used a small pointed bit of some kind to etch in the outline. For the foglights I will try to do the factory symbol for foglights. For the DRL's I guess just a circle with "ray" lines coming off it. For the stero I guess a speaker icon would work nicely for that.

I'll do a posting on the results of all this when the relays come in about 3 weeks or so. Shipping from China isn't fast, but it usually is a very cheap alternative. DCO.
 

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Discussion Starter #13
DreamCarOwner- Good for you for going forward. Let me know if you need a wiring diagram for the button bank. Yes, I used a very small tip to make the icons. It was a diamond dust tip I had laying around. I suppose you could also use a very small Xacto blade and "scratch/scrape" the paint off. Here's an idea.... Spray some flat black paint onto a scrap piece of hard plastic and practice on that. Search Google for automotive switch icons, and you'll find all sorts of pics for them you can use. I merely took a screen shot of the icon pages I liked and then enlarged or shrank the screen shot til I got the icon size I wanted when it printed out. If you have any other questions, just ask and for sure post how it went for you.
 

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Misfitsailor and DreamCarOwner-


I'm all too happy to help you out! As you've already determined, the wiring diagram the seller provides is a bit confusing. Hopefully, my modified wiring diagram will make more sense to you. When I first worked on this modification, I tested the whole thing on my bench using a simple LED as the "Device" because I too didn't trust the wiring diagram the seller provided. I suggest you bench test everything too, just to make sure you have everything wired correctly before you attempt to install all of this in your car. (You don't have to use an LED thou. Any other low amperage 12V, device, which turns on/off immediately, should work.)


Now, I don't think that paying attention to the polarity of the wires that come from your button bank terminals to the "Trigger" really matter. (I'm not 100% certain of this however. The notes I took don't address this, and my car that has this modification is stored 100 miles away for the winter, so I can't see what I did.) :-( For example, on the button bank, the factory switch for the fog lights uses Pin #3 , which is supposed to be "ground", and Pin #8 for "positive". I think I simply hooked up the two "Low Level Trigger" wires that came with the relay and connected them to these two Pins, not caring which was "ground" or "positive". (I'm thinking you don't have to worry about the polarity of the "Trigger" because you're bypassing the SAM to control, for example, fog lights.) If for some reason the "Test Key" bench tests okay, but when you hook up the "Trigger" and it doesn't work, reverse the wires of the "Trigger" and try it again.


When you bench test your set-up, I also highly recommend during your bench tests that you use the "Test Key" button first, before you connect the "Trigger" to your button bank. Again, this is just taking the more cautious route, so you don't accidentally fry something, or if you do fry something, it'll be on your bench and not in your car! (IMHO the risk of frying the latch relay is really low. I did all sorts of experimenting trying to figure out how to wire this up and I didn't hurt my latch relay.)


Once you've got everything hooked up correctly, you will also find that you can't just simply "stab", or quickly press the "Trigger" button or the applicable switch on your button bank. You actually have to press the button/switch down for about a second, allowing enough time for the latch relay to make the circuits in the latch relay do what they're supposed to do. You'll get used to it. I hope all of this makes sense, and of course, let me know if you have any more questions or better yet, when you get it working.
 

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Discussion Starter #17
For all of you that are following this Post, here's the Pin numbers of what I consider the available button bank switches. Note- I don't know what the corresponding Pin numbers are for Switches #1 & #6 . Besides, those two switches are used for the heated seats, which seems to be a commonly added factory option. Also, since Switch #1 & #6 (or at least the SAM ciruits) are two position switches/circuits, (1 for low heat, 1 for high heat), I wouldn't recommend using Switch #1 or #6 . Please refer to Posting #5 for an illustration of the below list of available Switch numbers:


Switch #2- Pin #3 is ground. Pin # 8 is 'hot' or 'positive'.
Switch #3 - Pin #3 is ground. Pin # 9 is 'hot' or 'positive'.
Switch #4- Pin #3 is ground. Pin # 13 is 'hot' or 'positive'.
Switch #5 - Pin #3 is ground. Pin # 14 is 'hot' or 'positive'.


I hope this helps all of you!
 

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Thank you Limoak for the additional information. I'm right in the middle of getting my new radio (headunit) installed and thank you MisfitSailor for all the advice on finding a suitable installation kit for slightly oversized 2 din radios. I took your advice and the Metra kit works and matches wonderfully. As soon as the stereo installation is finished, it's on to the latch relays and the button bank mods. I will keep everyone posted of the results and maybe a video or two. DCO.
 
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