latched on/off output

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mr_malina

Member - Posts: 7

Joined: August 03, 2012

Location: Ohio, United States

Posted: August 03, 2012 at 3:35 PM / IP Logged

I am attempting to do the following relay setup. I am wanting to use a 12V+ ignition wire to activate the setup and for it to return to a off position after the ignition looses power. Is there a way to do that with this setup or would I have to add a additional relay to the ignition wire? Thanks

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: August 03, 2012 at 7:39 PM / IP Logged

Yes - just use ONE relay that is energised (#86) from IGN +12V.

BTW - that is not latching. It is a typical relay circuit which is on when its control or signal wire is on.

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: August 04, 2012 at 12:58 AM / IP Logged

And if you do want to latch it see some posts below.

mr_malina

Member - Posts: 7

Joined: August 03, 2012

Location: Ohio, United States

Posted: August 05, 2012 at 1:07 PM / IP Logged

Maybe I am thinking about this wrong, I will let know what I am trying to accomplish. I am installing OEM A/C in one of my vehicles that did not come with it. I want to be able to turn on the A/C with the push of a button and turn it off with a push of a button but only when ignition is on. I also want if the A/C is on when the vehicle is shut down when it is started next time it goes to off by default. It appeared to me that I could accomplish this with relay setup pictured above, but this is over my head. It would also have to have a positive output, prefer for positive input and not worried about switch.

mr_malina

Member - Posts: 7

Joined: August 03, 2012

Location: Ohio, United States

Posted: August 05, 2012 at 1:08 PM / IP Logged

Cant read apparently ^^^

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: August 06, 2012 at 3:15 AM / IP Logged

That's different to what you originally described.

How's:...?

That diagram's +12V should be IGN +12V so that it deactivates with IGN off.

The "+12V out" can be the aircon if that IGN +12V has enough current rating, though I'd probably recommend the 12V out feeds another relay (#86) that connects an appropriate or new fused +12V from the battery (#30) to the aircon (#87).

The second relay not only takes the load of the "latching relay's" IGN +12V, but also allows future signals to kill the aircon - eg, aircons often turn off at low revs or idle. IE - a low RPM signal could break the 2nd relay's GND (#85) or +12V signal (#86).

FYI - that diagram exists in various places, but the12volt's capacitor value for latching relay? 8th reply includes its wiring diagram with added description.

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: August 06, 2012 at 4:15 AM / IP Logged

How can you run the AC if the engine is off?

The compressor needs the engine running.

A latching relay buy the way is what the vehicle manufacturer would use.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: August 06, 2012 at 4:33 AM / IP Logged

Agreed about the ac not running with the engine off, but those I have seen (ie, usually Japanese) disable the ac clutch during cranking etc.

Hence many use the "usual" charge (light) circuit with added cutouts for idle and sometimes cranking.

The Japs I have seen use normal relays, though sometimes using the DPST with NO & NC contacts for cranking interlocks etc. I have yet to see latching relays used, but you know I avoid VAGs etc.

howie ll

Pot Metal - Posts: 16,466

Joined: January 09, 2007

Location: United Kingdom

Posted: August 06, 2012 at 4:49 AM / IP Logged

He wants one touch, I was thinking of items which use one momentary button such as rear defog, that requires a latcher or at least a solid state latching circuit.

This all sounds like a bit of Heath Robinson, = a Kludge to me.

Why not just buy a retro kit, there are still manufacturers in the, US, South Africa and Israel.

Heck up to 7-8 years aqo when we were still installing them we used an English supplier.

In the US try ARA.

Note unless going into a Japanese Vehicle which has ready prepared wiring, compressor mount etc. this is a 3-4 day job for an EXPERT who is that rare beast, a good mech. and a good sparks.

Under engine block, drop either alternator or power steering compressor, mount AC bracket or change existing.

Fit new drive belt.

Drill 2-3" holes (2) in bulkhead, drop AC h/exchanger in front of rad, dashboard out, loads of wiring etc. etc. etc.

And don't forget back in the day we could pull an E36 dashboard in about 20 minutes, i.e. strip from floor to windscreen.

We stopped that part in about 98, after that everything in the UK got air ex factory.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: August 06, 2012 at 5:32 AM / IP Logged

I missed the single button....

In that case...

... where the circuit is powered by IGN +12V.

And the output controls the relay.

I suspect it powers up in the on state (+12V out), hence connect that to a relay connected to IGN +12V...

Or any flip-flip or divide-by-2 circuit (eg, the CD4017 can be div-2 to div-10 etc).

Or an on-off switch - push-button or rotary...

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