| jwadle |
Just wanted to ask what I think is a pretty dumb question, but I want to be sure...
If I connect two power wires together is it still ony 12 volts, or is it more and will damage the componant?
the reason I ask is that I connected my nav converter to the wire that is powered when it is in reverse (so I can have the camera come on) but it is still connected to the power switch... my fear is that I may leave the switch on, then put the car in reverse and ruin th converter.
Thanks for any help |
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| G. COLTON |
You never are going to get anything over 12 volts. I cannot tell from your description but the danger here is that you will short the system if you are not careful.
G |
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| 04mdx4sq |
| As long as you are dealing with only 1 battery, 12 volts is 12 volts, (batteries actually rest at 12.6v, but this is not the issue). without the use of a step up device, it doesn't add more voltage to add more 12v lines to it. The potential problem with doing this lies in the fact that some wires that will show 12v when triggered will rest at ground, thus causing a short or worse. When wiring in a situation such as this, I would recommend using a SPDT relay to isolate the wires (this is a common relay you should be able to get at any stereo shop). In the following diagram of the relay, you would hook 30 to a fused constant 12v, 87 to the wire that you want to feed 12v into, 86 to your 12v trigger, and 85 to ground. This will isolate the wires and prevent feeding 12v into a circuit that may need to rest at ground. |
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| mdxx3 |
| Anyone here votes for adding 2 diodes to the circuit? (Re: reverse lights outside/rear may be on when the switch is on(??)) |
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| 04mdx4sq |
| The problems with diodes on potentialy sensitive computer systems are leakage and current capacity. Some wires in a car are data bus wires that do different functions by changing the voltage present on the wire. I like to use relays due to the fact there is no leakage and their ability to carry higher current. On sensitive circuts, I do use a diode, but it is across the coil of the relay where it lets the coil field collapse without the potential for a spike. With all of the new computer systems in cars, I have become cautious in my approach, a relay is a lot less expensive than a computer. Just my 2 cents. |
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| mdxx3 |
No.. no.. I mean diodes in Jwadle's "original" circuit/idea (we both must have Replied at the same time earlier and yours showed up first). What I'm thinking is... the switch goes to the diode to the component. The reverse 12V goes to the second diode to the same component, and both circuits will now be "isolated" from each other. There'll be a small voltage drop across the diode but should be negligible anyways. (All this is if it's the positive-triggered type. The diode can be the 50 OR 100 PIV type.)
I don't think a data bus pin/wire has enough current to drive an automotive relay(??) It'll now involve transistors etc and Jwadle will wanna kill us for giving him more work:)
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| jwadle |
Thanks everyone for your replies.. Well let me ask you one thing.. If indeed the circuit needed to rest at ground and I hooked it up the way I said, and had the switch on and the car in reverse (2 powers on), would the short happen right away?.. I guess what I am trying to say is that I already connected it this way last night and did a quick test and had no issue.. I conencted it to the reverse wire on nav system on my 2001, it was green with silver and was on the last connector to the left.. After reading these replys I disconencted it..
I am home sick today, so I have not driven it yet... I hope I did not fry anything.. |
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| mdxx3 |
Good thing you took it out for now. Both power lines on should not short it (should be safe).
But having the switch on and the converter off (not in reverse) may be questionable if the 12V from the switch goes back into the converter circuit that's supposed to stay off (we now know it's not to the lights at the back but to the converter; ignore my first message earlier) Anyone else here can think of anything or help solve this? Need relay, diodes or it's perfectly fine the way Jwadle wired it? If relay or diodes, how would you wire this item? |
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| 04mdx4sq |
| I think I may be missing exactly what you are doing, is this involving putting video into the nav monitor, then having a second source (the rear view cam) run into the monitor when reverse is engaged? A few more details might make it easier to make a suggestion. |
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| jwadle |
Wow you guys are great... Posted the last replay from my Treo from the couch, so I my thumbs got tired before I explained it well.
Ok this is what I have;
I have a coverter under the front seat (not the Sam unit, but a kit that I had to solder together). I have it hooked up to a switch locaed in the center consol. Power comes from the cig lighter to the switch, then to the converter. I just got a rearview camera. I found the wire that is powered when in reverse on the nav unit itself. I connected a second wire to that, then connected it to the power on the converted box. So when I put it in reverse, the converter box comes on and the screen switches from NAV to the video from the camera. Like I said, I already did this and nothing "blew up" but as I think about it more (and thing about what you guys posted) it may make more sense to do the relay. I belive the wire controls the reverse indicator to the computer. Meaning when you go into that "easter egg" diag screen, and go to a certain diag menu it show indications for a couple of things, like, if the lights are on, if the parking break is on and if it is in reverse... I think at the very least if I have the "back feed" tot his wire it may show the car is always in reverse if the converter is on... I know I should not drive with the video screenon, but I only do it to change MP3s.
Thanks for your help with all of this... I am going to get that relay and hook it up right.. Better safe than sorry. |
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| 04mdx4sq |
quote:
Originally posted by jwadle
Thanks for your help with all of this... I am going to get that relay and hook it up right.. Better safe than sorry.
Not a problem. I have definitely adopted that same approach to modern auto electronics. |
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| mdxx3 |
Jwadle,
I took out the 04 Service Manual to double-check the schematics, etc. Give me some time to draw two sample circuits - one with 2 diodes and one with a relay (after that, you figure which one you want:)) |
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| jwadle |
| OK I just got the relay and some dioads... I am pretty sure I got the right relay, but not so sure I got the right dioeds... if you could give me suggestions from radio shack I will make sure I got the right one.. the guy there had no clue...yea they have answers... thanks agin for your help with this as you can tell while I will do just about anything to the X myself I somtimes don't have all the knowledge |
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| mdxx3 |
The 1N4001, 1N4002 or 1N4003 or any equivalent diodes will do. If you have something else, just let me know and I can check their datasheets. (Hang on in there. I'm still working on the second sample circuit, but the first one is ready.)
Here are a couple of random notes before I get to the circuits:
The wire color is GRN/BLK for 04 (and 03 model ) instead of the GRN/silver that you mentioned, but it's at the corner (pin 5 of 8, with 7 pins populated). Signal name is "BACK LT". In reverse gear, it is at battery voltage (12V), and otherwise it's at 0V (ground).
- That pin/wire where you found the reverse signal is an input into the navi box. The output is from the same circuit that powers up the reverse lights (which means my first guess earlier yesterday is correct and said "two diodes").
- Also means on the first try the other day, the reverse/back-up lights behind the MDX were on when you hit the switch, but you probably wouldn't notice these reverse lights that day unless you were standing behind the MDX.
- That circuit where you tap is considered "high current" to a small extent. It is not a data bus in any way but just a wire (not "low current" signal). Up to 10A (maybe 120W to 140W max, it's fused) is supplied to the reverse lights (both sides, 18W each), trailer hitch connector/extender, navi input, and auto-dimming mirror inside the vehicle. You can even power your board and other stuff with this wire as long as it's not that many watts but still depending on the wire gauge/size (but it is not 10A on the wire behind the navi box - it's 10A total for the back-up lights, trailer hitch connector/extender, navi input, etc).
- It will not harm the rest of the car (or navi box) like what you did on the first try the other day. People driving behind you will get confused when they see your car going forward while the reverse lights are on, but you didn't take it out on the streets - so no biggie here.
- Your navi box is safe. I'm 99.9% sure it didn't get fried (because it's an input, and your 12V lit-up the lights at the back and that's no biggie).
- If you have navi on (entered a destination to go), and on the way there, you decide to view this camera/alternate, the navi software _may_ get confused because of the reverse signal (will not damage anything electrically, but the software/firmware may not like it or get confused thinking the car is is going in reverse. (This part is iffy - you'll have to double-check after you get everything in later.)
- Must add 2 diodes for sure, or use a relay (your choice, later).
- I'll pass you 2 circuits (one with 2 diodes, and the other with a relay - you pick one). Below is the first of the two sample circuits with 2 diodes. (The second one is not ready yet.) |
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| mdxx3 |
Maybe I should explain a little more first while that circuit is there (because I dunno when the second circuit will show up, but it will)...
Diode 2 in that picture is so that the voltage from your switch does not go into the Reverse Gear circuit and light up the back-up/reverse lights. There are also other items on that same circuit per the service manual.
Diode 1 is so that the voltage from the reverse/back-up circuit does not go this other direction and back into the 12V ignition source (12V cig lighter port, or ignition)
TTYL... |
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| 04mdx4sq |
| Here is a simple relay on the system. In this system, take the wire from the cig lighter to the switch and cut it. Take the cig lighter side to terminal #30, take the other side (to the switch) to terminal #87a. Terminal #86 would be the reverse trigger wire, #85 goes to ground, and #87 would go to the video converter box. Hope this helps. |
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| 04mdx4sq |
| Nice diagram, mdxx3. We seem to keep posting at the same time. |
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| mdxx3 |
| Yah... we seem to be posting at the same time! :) |
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| mdxx3 |
04mdx4sq,
Any chance you can do a drawing for Jwadle? Because I was following your description and was wondering which pin/wire goes to the Acura navi box (the Reverse Wire from Navi part). From your description and relay drawing, we get power to trigger the relay's coil from this Reverse Wire. This sends 12V to the Jwadle board. The missing part is I think we need to send 12V back to that wire so that this navi box will activate the input (or no video input on screen when he manually tries his camera) because isn't the "Reverse Wire from Nav" supposed to be an input at the navi box. I think it's not an output; the output is from the 10A relay on page 22-127 of the 04 Service Manual. From the way it looks, it seems you may be using the relay to provide power to the video converter box when it's in reverse gear, but when Jwadle switches it on manually, it does not seem like it will activate the Acura navi box(??). Please help to double-check on this.(??)
{I found the pin description is on page 22-398. Basically says this BACK LT (reverse gear) voltage comes from the transmission - when we shift into reverse, the transmission or gear stick circuit puts out 12V for this signal.}
Thanks! |
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| mdxx3 |
Sorry for the delay. Had company over for dinner earlier and then the Kings/Knicks game was on ( :claphead: )
Below is the sample circuit with the relay. Kindly note that this circuit is different from the one that 04mdx4sq mentioned.
In my sample circuit shown below here... when you hit the switch, it sends power to your converter board, and at the same time sends power to the relay's solenoid and swings that circuit over (87 and 30 will now be connected). This feeds 12V into the Acura navi box to activate the video input. Note that you'll have to cut that "BACK LT" wire to insert this relay (also similarly have to cut that wire to insert that diode in sample A earlier).
If you do not have the switch on (ie. it's now off or open circuit there), then the 87a and 30 will be connected and the Reverse will function as usual.
Good luck and have fun! |
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| 04mdx4sq |
| What I meant is tap not cut the reverse wire from the nav system, and when the reverse wire energizes, it will energize the relay coil, so the video unit sees 12v and turns on. The line to the switch to manually turn on the video unit will have 12v (when the reverse wire is not energized) to the switch, so when the switch is off the unit is off and when the switch is on the unit sees 12v, but when the nav reverse wire is energized, no power goes to the switch as that terminal on the relay becomes open, so it cannot back feed into the nav system wire. I am not the master schematic artist, so if need be I will try to work on one, but hopefully this post will clear up what I was trying to say. |
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| 04mdx4sq |
| Both designs for relays would essentialy achieve the same effect, just by different routes. My only concern with the way mdxx3 does this, if the wire that shows 12v when in reverse has any function with the car in any gear other than reverse, the wire is essentialy no longer connected to the nav box. I don't know if this is an issue in this instance, but that is why I designed the circut the way I did. The potential problem with my design is that if there are any voltage pulses from a data bus system on the trigger wire, it may cause the relay to act irraticaly, turning on and off the video unit. I guess the best advice is to try one setup, if it works with no glitches, go with it. If not try the other. Either setup will at least isolate your two 12v power leads, which is what the post started out as......:4: |
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| 04mdx4sq |
| Okay, here is what I was proposing (mdxx3, hope you don't mind me using your drawing as a basis, it is very clear, much better than my attempt). Hope it helps. |
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| mdxx3 |
04mdx4sq,
If you can kindly check page 22-127 of the 2004 Service Manual, you can see it is not a data bus, so you may want to not think of it as data bus. We need to understand the fundamentals so that the outcome can be predictable. Also, another thread here, http://www.acuramdx.org/forums/show...&threadid=20092 , shows a diagram provided by Nhatman/URIRx98, and the "BACK LT" or reverse light is also cut, a switch is inserted, and this "wire is essentially no longer connected to the nav box" as you have mentioned. I'm pretty sure there is a good reason or similar reason they did that. Seriously we all should ask 04mdx4sq to put up a schematics for peer review and also this may allow Jwadle match what he's doing(?) For a start can others (all the circuit experts) here please start doing a peer review on this entire thread - double check if anything anyone said makes sense before Jwadle gets into trouble?? |
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| mdxx3 |
| Uh oh. we posted at the same time again!! Let me read your diagram now (it's always ok to use my schematics - everything here is shareware!) |
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| mdxx3 |
| Ok, I just looked at your schematics... I got the same issue that I mentioned earlier. I think that Acura Navi will not activate its video inputs - need to assert (also isolate) that pin on the navi box so that the screen will switch views to camera/custom-view. If I follow your drawing, we can save on some parts (remove the relay) and hook Jwadle's custom board/module straight into the 12V ignition (via a fuse and a switch). But the issue is the display (altenate view/camera) can only work in reverse gear but Jwadle likes it to work when he toggles the switch, right? What do you guys think? (Come on... we need peer review from all the tech guys here!) |
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| 04mdx4sq |
| Okay, I see what you are saying. My relay was just to isolate the nav 12v reverse trigger from the 12v power lead to the video unit so there wouldn't be 12v backfeeding into the nav wire. I am not sure how the reverse cam is wired into the system, I guess that is my next question. Is the input done though a nav/ factory camera input, or does it connect to the aftermarket unit and what causes the input to switch. If the sysem needs 12v input to allow it to switch to the input, you are correct, and my system wouldn't work. |
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| jwadle |
| I just have to say WOW thanks again.... My wife is amazed (as am I) as to how much work you guys are putting into this.. Well I like the Diode way the best (just seems easier). I bout the correct diodes and will be installing this tomorrow morning.. I will let you all know how it turns out.. |
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| mdxx3 |
No... don't thank anyone yet. First you'll have to get it to work. Then share lots of pictures of the install!! (Everything is shareware and also open source here.) You mentioned soldering iron - of course now I'm curious to see what that board/kit it is...!
No relay is quieter - no click sounds. If your board/kit draws "a lot of power", you can use the larger diodes or parallel the smaller ones.
Have fun! |
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| jwadle |
Well I just got done installing the Diodes.. I used the larger 1N4002 diodes.. And guess what?? Everything works.. No reverse lights with the switch on. I installed one diode at the switch and one at the reverse trigger coming off the nav box.. just like you said.. I made sure it worked (meaning that it blocked the voltage) by using a lamp.. Now all I have to do is install the camera and run the wires... But at lease now I know it will work..
Thanks again for all your help with this.. I attached a Apple Qucik time movie of it working... The extension is 3g2, its a Treo 650 camcorder format, but QT will play it.. |
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| jwadle |
| Here are some pictures also.. I could not figure out how to post the pictures in the thread itslef... |
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| mdxx3 |
Nice video and pictures!! Thanks! Congratulations on getting it to work! :29:
Sorry... now we want to know more... Can we have more photos please?? Yeah... because there's Windows XP and Windows Media Player in there!! Kindly show us more pictures including the computer (and tell us a little bit more about yourself... tech/engineer, hobbyist or both?) Tell us more about that converter box too. Thanks! |
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| jwadle |
Sorry it took so long to post, well right after I finished the work on the MDX I got laid off from my job. I was the Manager of Information Systems for a Paramedical education company in CT.. So after I got done laying off 2 of my people, and disabling accounts for 17 others that got laid off, I got the axe also.. Oh well.. Sucks, but the company has been going down for almost 3 years.. Every year we had lay offs.. Almost a relief.. So I have been looking for a job every since… So if anyone is in CT and knows of any openings let me know..
No on to the important stuff… I connected an old IBM laptop that had the LCD screen cracked to it the converter box. I used a VGA to NTSC adapter which connects to the laptop so you can show it on a TV (or in this case the NAV screen). I then bought a blitz tech adapter and connected it to CD changer port on the radio.. Sounds great.. I connected a USB Bluetooth adapter and use my Treo 650 to connect to the internet.
I also have a TV tuner, and one diversity antenna connected.. I live down by the shore line and I get pretty good reception.
That’s about it… I will try to post more pictures soon. |
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