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latch on/off same momentary feed


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wez80 
Member - Posts: 3
Member spacespace
Joined: January 30, 2012
Posted: January 30, 2012 at 2:19 PM / IP Logged  
Hi folks...
Excellent site, very informative and deffinatly bookmarked!
I've been building a motorhome and managed all the circuitry fine, this ones got me though...
I would like a 12v LED light on the outside of my campervan above the door, there is loads out there on ebay that will do the job.
The problem is, i'd like to turn it on and off via the remote for my universal central locking kit.
I havent actually fitted the remote locking kit yet, I can do that no problem, but on the kit i've bought, the keyfob has 3 buttons: lock/unlock and 'trunk(boot) pop'.
I'd like to use the 'trunk pop' button to turn the outside light on/off from afar (handy when coming back to the van at night)
The 'trunk pop' feed wire from the central locking control box provides +12v for 1 second, great if you want to power an actuator/solenoid, but not much use having your light on for 1 sec! lol
Is there a relay that will take this momentary +12v and 'latch on' so the lighting circuit stays powered, then with the same +12v feed from the remote locking, 'latch off' and turn off the light when I press the 'trunk pop' button again.
I have looked for about 20mins on the net, i've seen latching relays that sound almost ideal, except they latch with a momentary feed, then unlatch with a seperate momentary feed.
I need the latch/unlatch to happen with the same +12v feed.
I'm usually good at this stuff, but this has got me beat, i know i could probably make a timer circuit to flip/flop the feeds, but that circuit itself will draw power, and I like simple oldskool mechanical relays if its do-able.
The relays (mentioned above) that i've seen only draw power when actually changing state.
Hope that makes sence to someone, and I havent rambled too much lol
Cheers,
Wez.
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: January 30, 2012 at 4:52 PM / IP Logged  
DEI 528t or 611T either or both will send a signal for up to 3 minutes, work off POS or NEG triggers or the 611T can be set to latched where it will stay on until you hit that remote a second time.
Ween 
Platinum - Posts: 1,326
Platinum spacespace
Joined: August 01, 2004
Location: Illinois, United States
Posted: January 30, 2012 at 6:02 PM / IP Logged  
hi,
for your old school latching relay, look for a old vw headlight dimmer relay...or something such as this:   http://www./itm/270903852254?
only issue you may have is the current available on your keyless module outputs
mark
oldspark 
Gold - Posts: 4,913
Gold spacespace
Joined: November 03, 2008
Location: Australia
Posted: January 31, 2012 at 1:27 AM / IP Logged  
Apparently there are "one wire" pulse-latching relays. Alas, I've only used the other single-wire type (voltage reversal unlatches).
But various cars used their own "pulse" latchers - usually as Ween indicated - for the pulsed hi-low beam stalks etc. SAAB also have them (the big orange relay). In fact any modern vehicle with a "pull to change" hi-lo beam stalk should. (Some older vehicles used special mechanical relays. Hopefully that ceased and all are now plain relays controlled by electronics.)
But mechanically latching relays are nice in that they do not draw current except when changing. "Normal" relays may take 250mA or more to close the contacts (though that could be reduced, but it's still far from "zero"). (Ironic for a load that probably takes less current!)
Or there's flip-flops or transistors that drive the lamp itself (negligible current).
ashbyspannerman 
Member - Posts: 18
Member spacespace
Joined: August 22, 2004
Location: United Kingdom
Posted: February 05, 2012 at 2:47 PM / IP Logged  
surely the latched relay diagram here would do the job perfectly
https://www.the12volt.com/relays/page5.asp
wez80 
Member - Posts: 3
Member spacespace
Joined: January 30, 2012
Posted: February 05, 2012 at 4:39 PM / IP Logged  
ashbyspannerman wrote:
surely the latched relay diagram here would do the job perfectly
https://www.the12volt.com/relays/page5.asp
In that diagram, it would appear that the momentary feed is ground (negative).
The remote locking kit i've got outputs a +ve feed.
Could the diagram be adapted?
wez80 
Member - Posts: 3
Member spacespace
Joined: January 30, 2012
Posted: February 05, 2012 at 4:48 PM / IP Logged  
Sorry, forgot to say, i've also searched about for info the hi-low beam relays, they too all seem to be -ve trigger according to other forums that google brought up.
And the DEI setup seems quite expensive, I can only find the on ebay usa, and i'm in UK.
Many thnaks for your help though guys :D
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: February 05, 2012 at 5:10 PM / IP Logged  
Simple, make the left relay terminal 85, take it to ground (earth), trigger pos to 86 and turn that diode around.
Only problem with that set-up is how do you turn it off?
528t and 611t are available from armourauto.com in the UK.
Incidentally, I've never heard of any reputable keyless entry system with a pos trunk output they all have a low current (under 200 milliamps) NEG output. I believe Compustar in Canada also gives you a 10 amp POS.
Actually quite simple, use your k/entry unlock to turn it on and the trunk pop to turn it off. Use them to feed a dual coil latching relay, Omron G6CK-2114O-US12DC available from RS components, Mouser or Farnell, all available in the UK. You can use NEG or POS triggers, at least 5amp switch capacity.
howie ll 
Pot Metal - Posts: 16,466
Pot Metal spacespace
Joined: January 09, 2007
Location: United Kingdom
Posted: February 05, 2012 at 5:27 PM / IP Logged  
Here you go:- DFZ_latch.bmp
Dead simple I'm assuming pos unlock motor wire or unlock trigger.
If it was NEG, just join the constant 12V+ to the plus side of that coil and bring the trigger to the NEG side.
Note, I said the green wire was LOCK in the diagram, it should of course have said UNLOCK.
js305 
Member - Posts: 26
Member spacespace
Joined: April 29, 2007
Location: United States
Posted: February 14, 2012 at 9:34 PM / IP Logged  
I know this hasn't been addressed for a few days, but there is a very simple device that will work here. You have a single 12 volt pulse to change the state of something each time you push the button, right?
Look at the NTE RLY76/77
http://www.nteinc.com/relay_web/pdf/RLY76_77.pdf
They are available from a lot of places. I think the cost is maybe $25 or less. It's really two relays fastened to a solenoid. No power is consumed in either state. These things were designed for circuits like garage door openers used to use before all the electronics got involved.
Joe in Texas
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