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Discussion Starter #1
I have a 12v accessory that powers on/off on the 12V ACC currently. I'd like to figure out a way to make it work differently, however:

When the car is turned on, the device does NOT turn on.

When I press a button AND the car is on, the device turns on

When I turn off the car, the device turns off.

... A simple toggle (on/off) switch wouldn't work, as I want to be able to turn the device on with the car started, but if I turn off the car and turn it back on, then the device shouldn't power up. With my limited knowledge, it seems I'd need to use a momentary switch/button, and a relay that provides power to itself. So, if I press the button, it activates the relay, and then the relay, once latched, keeps itself latched. ie:

12v ACC -> button (normal off) -> diode -> relay magnet

12v ACC -> relay latched -> diode -> relay magnet
12v ACC -> relay latched -> device

Does that make sense? Would it work? Can one of you 12v guru's explain what I'd need to do this and how I'd go about doing it?

Thanks
Gary
 

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need more info on what the device is...and when you say *press a button* do you mean a remote button? or a button on the dash?

Initially, i'd say, you'd need a latching relay, but without more info on the device itself, hard to say exactly.
 

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Discussion Starter #3
The device itself is a harman/kardon drive+play. Currently wired, it takes a ground, a 12v constant, and 12v ACC. When the 12vACC is on, the device turns itself on. When the 12vACC drops, the device powers itself off.

The purpose in doing all this is that I don't want the drive+play to ALWAYS power itself on when I turn the car on. Instead, I want to have to hit a button (on the dash) to turn it on. Every time I start the car, I want to have to hit the button to turn it on.

Please forgive my ignorance... I know what a basic relay is - what is a latching relay?
 

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ahh i see, then it's a very simple fix. No need for a lacthing relay.

Simply add a switch/button and a relay inline with the drive+play ACC wire. The relay *might* be overkill, as i don't see much current being pulled by the drive+play...but it can't hurt. And by using a relay, you can get any switch/button that will compliment the dash, does not need to be heavy duty or some big ugly toggle.


Tap the ACC car wire and connect to the switch/button and then to relay pin #86

connect chassis ground to relay pin #85 (can be combined with the drive+play's ground, providing it's a chassis ground and you didn't just tap a ground wire)

Tap the 12v constant car wire (with fuse the same size as the drive+play uses on its 12v power wire) and connect that to relay pin #87
You can use the same car wire that is used for the Drive+play's power, but tap the CARs wire, not the drive+play wire.

connect the drive+play ACC wire to relay pin #30
 

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Discussion Starter #5
[quote author=AutoXer link=topic=69251.msg1200870#msg1200870 date=1171223277]connect the drive+play ACC wire to relay pin #30[/quote]

And now I get to show my true ignorance: What kind of relay would that be? I've never heard of relay pins being numbered like that. Perhaps a radio-shack link or something?

BTW, for 12v constant, I tapped into the fuse for the horn under the glove box. I used one of those things that you can plug into a fuse and gives you two fuse sockets and a hot wire. Is that a problem with the arrangement you described?

Thanks
Gary
 

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hehee, no worries man. I'm at work, but when i get home, i'll draw up an easy to follow pic of how it gets wired. It always seems more complicated when written out in text :)

In the meantime, i have an alarm FAQ on my website that has pics of the relay to use. It's a standard automotive Bosch style relay. Very commonly used in alarm and accessory installation.

ewwww, it may be my 15+ years as an installer, but i hate taps of any kind. The best way to make connections is to solder... There are very few exceptions that i'll use some form of tap. Also the problem with fusebox taps is that they expand the pins and when removed, the fuse may have intermittent issues... But no, it won't pose a problem with what i described.
 

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Discussion Starter #7
[quote author=AutoXer link=topic=69251.msg1201105#msg1201105 date=1171230706]In the meantime, i have an alarm FAQ on my website that has pics of the relay to use. It's a standard automotive Bosch style relay. Very commonly used in alarm and accessory installation.[/quote]
Hey, that web page is nice! Some useful info there...

For the above circuit, and diodes needed? Any good place to find chassis ground near the glove box on the 3? As for the relay: this type of relay stays "on" with only a pulse of power? I'm more accustomed to relays that need constant power to stay "on." (I always picture a relay as a spring loaded light switch... if you don't hold your finger against the switch (constant power), it turns itself off.) I assume I could buy this type of relay at pretty much any auto parts store...

The drive+play is rated at 500ma, and it's fused at 2amps.

Oh - and a short question on your website: You talk about driver door priority unlock... do DEI alarms support that? Looking at the "quick reference wiring guide" for this python 990, I don't a pin for that...

Again, thank you very much for all the help. Let me know if you get out to the D.C. area and I'll buy you a couple beers.
 

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No diodes needed...well you could put one across the relay coil (pins 85 & 86) or if you use the option method i describe below

Yes, any automotive store or alarm/stereo shop.

You are correct, this relay requires a constant on both pins 85 and 86 to stay latched. Which requires a switch. If you'd prefer a momentary button, then a latching relay is required. The first pulse (press of the button) will *latch* the relay, and the second pulse will *unlatch* the relay. As for purchasing, DigiKey or Mouser i guess.... i always got them direct from DEI.

Yes, DEI alarms support priority unlock.
H1/3 White/Blue 200ma (-) channel 3 output
This output can be programmed for priority unlock.

Now, this output can also be programmed as a latched output. BUT, you can only use the 3rd channel output for one action, so you'd have to decide which is more important to you, priority unlock or a fancy turn on for the D+P. This can be combined with the dash switch, but diodes will be needed. (outlined in red in the above pic. If not using this method, just connect the switch directly to the relay pin)

If you pull the passenger kick panel, you'll see a few factory chassis grounds, use a ring connector and bolt it with one of them.

EDIT: BTW, The diagram does not follow excatly what i posted earlier...as now you mention you have a DEI alarm, so to make it easier, incase you decide to go with both options, i changed it up.
 

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Discussion Starter #9
[quote author=AutoXer link=topic=69251.msg1201470#msg1201470 date=1171245291]You are correct, this relay requires a constant on both pins 85 and 86 to stay latched. Which requires a switch. If you'd prefer a momentary button, then a latching relay is required. The first pulse (press of the button) will *latch* the relay, and the second pulse will *unlatch* the relay. As for purchasing, DigiKey or Mouser i guess.... i always got them direct from DEI.[/quote]

I guess a latching relay then. It'd make for a cleaner interface. One thing: I think I might have confused the issue by mentioning the alarm. I've actually started talking about the DEI thing in another thread (see below);) I don't want the D+P in any way associated with the alarm. I just don't want it to EVER turn on when I turn on the car...

I go outside and turn on the car. D+P stays off. I hear the morning traffic report, and want to switch to the D+P - so hit 'media' on my dash and press a button mounted on the dash.. the D+P comes back on. I get to work and turn off the car (but don't hit any switches.) D+P shuts down. 16 hours later (it seems) I get out and start the car again. The D+P shouldn't turn back on, but should wait for me to hit a button.

Moved the DEI unlock priority stuff to another thread I started talking about it:
http://www.mazda3forums.com/index.php?topic=69131.msg1201575#msg1201575

BTW, I _really_ appreciate the help with both the circuit wiring stuff, and the DEI stuff. I've decided that the reason most installers refuse to talk are that they simply don't know how to do it. (I've had installers tell me that dual-stage (aka driver priority unlock) is impossible on the 3.)

Thanks
Gary
 

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as long as the lacthing relay is connected to a switched 12v source, (i.e. no power when key is off) thats how it should work. It's been years since i worked with latching relays, seeing as DEI alarms have the option onboard...so i may need to edit this post....lol

Also, FYI, the above relay diagram, where it shows a 12v connection, that should read 12v switched fused 2amps. I'm too lazy to go back and change it ;) I know you aren't going to use it, but somebody else viewing this thread might.
 
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