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Thread: [resolved] timed relay.... keeping voltage when origional connection broken....

  1. #11
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    Quote Originally Posted by Curiosity View Post
    You should get under the dash and find the BCM. Then grab a DMM and start poking around. Usually you can stick a probe in the back of the connector to make contact. Write down all the pins and volts or if no volts, if grounded and make note of any changes when armed/disarmed/locked/unlocked. Also google for alarm installs for your make/model. The DIY instructions can help with what wires do what. After that you might have some new ideas that will make it easier.

    hey ya. thanks for input it is appriciated - believe me, but i dont need to mess with the BCM or get a m/m as i already know all of the wires etc... i installed the remote locking kit myself - since it had clear instructions of "yellow wire to source of command for lock, yellow/black to source command for unlock, blue to lock wire, green to unlock wire red is live, black is negative, 2xpurple to lights, pink to horn ... clear, simple and easy - just a couple of hours work getting into the wires [plus the crap out when i inadvertantly unplugged my airbag - luckily my bro told me how to reset it so it was all good without deploying when i plugged it back in :P] - only problem being the horn is actually a live not a negative pulse, so i need to switch it to a ground pulse via a relay or sumat but later for that, when i need to disconnect mess again :P

    just to clarifiy before i go messing - i dont see how i can fry anything on my car as long as i fuse the live wire, but how much power will a siren ground - it is a 300ma siren, and two relays n the SCR require. will a 1A inline fuse suit? mind, all that will be powered by my live wire as in the diagram, will be the two relays, correct? the SCR doesnt draw power no? siren will be fused under bonnet seperately with a 1a inline fuse.

    i assume i need to fuse the relays yes? or would it be ok to just cut into the power AFTER the central locking fuse - 25A fuse, as it powers hazard lights horn, and pulse relays.

    now theres two things to this circut, any control mechanisms need to cut power or ground to the realy that has the horn, anythin you want to happen as a result of the alarm needs to go on the same circut as the horn itself.
    i get the bit of alarm on horn itself... control to break power or ground, as long as the ground is broken the scr will reset to off yes?
    when my central locking is locked it makes the starterkiller wire grounded when unlocked it breaks the ground. [it may be the other way round, in this case i would just use a five pin relay to switch it round and provide a relayed ground on the 87a pin :P that would suffice to breaking the circuit and cutting power, yes?

    Thanks.

  2. #12
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    Quote Originally Posted by wayneox View Post
    i get the bit of alarm on horn itself... control to break power or ground, as long as the ground is broken the scr will reset to off yes?
    when my central locking is locked it makes the starterkiller wire grounded when unlocked it breaks the ground. [it may be the other way round, in this case i would just use a five pin relay to switch it round and provide a relayed ground on the 87a pin :P that would suffice to breaking the circuit and cutting power, yes?

    Thanks.
    yes, the SCR will reset to off when current is no longer going through it. you're saying you're just going to wire it into the starterkiller, provided its ground? sounds like a plan to me. as for fuse, i'd just as well run a new wire with a 1A fuse, that should be plenty for a few relays and an SCR. i imagine the SCR would draw maybe a teeny bit of current itself, but i'd not worry about it.

  3. #13
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    Quote Originally Posted by gaoes View Post
    yes, the SCR will reset to off when current is no longer going through it. you're saying you're just going to wire it into the starterkiller, provided its ground? sounds like a plan to me. as for fuse, i'd just as well run a new wire with a 1A fuse, that should be plenty for a few relays and an SCR. i imagine the SCR would draw maybe a teeny bit of current itself, but i'd not worry about it.
    cheers. well ordered all the bits n bobs for it, including an extra cpl of relays for other things i plan - i might actually wire up a starter killer, as i saw a simple plan on another site where basically if the coil is grounded, [starter killer connection i will use for my alarm sys too] the starter wire wire from ig goes to coil pos and pin 30 of relay . so no power is drawn at all until the ignition starter is activated... as if relay is hot, the power goes to a blank 87, and if its not hot, it goes to a 30->87. seems like a plan to me for this. not that it really is needed, since my car has the immobiliser chip, but always good for extra stuff eh.

    cant remember site i saw it on, but basic wiring diag would be [if i remember correctly off hand the pin no's]
    86 ground
    85 from starter wire [cut origional connection!]
    30 from starter wire [key side]
    87 blank - if grounded, and try starting, the voltage goes no where...
    87a to starter [from origional cut wire

    i believe there is a second relay after the ignition key wiring - i may be wrong, but a starter draws quite a bit of power, so could even alter the origional relay wiring, but i'll prefer to keep it all under drivers kick space :P - hard to run wires to engine bay without drilling and all.

    but i think for now this thread can be considered as solved, as 1) my origional question is now resolved - i believe, and 2) i was given a far simpler - and i believe cheaper, resolution from my own idea - one that should work better too im sure

    so thanks, i will set up the siren etc n test a circuit in the house before hooking into car [from my 12v jump start battery :P] n let ya no if it works - hopefully it will :P

    cheers.

  4. #14
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    You could see the12volt's fuel cut off switch using cruise control (page 2, 3rd reply down) for a "self latching" SPST (or any) relay circuit in case SCRs get tricky etc (ie to turn of with DC supply still supplied).
    Not that in that drawing, the two input +12V supplies are usually the same.

    And FYI - though starter motors often take 200A-300A or about half that for reduction starters, their solenoids are usually around 20A.
    The solenoid is what the crank button (ignition key) supplies +12V to - though usually through a relay.
    But the "normal" current for a solenoid usually doubles if the motor's +12V in not connected (ie, if the Battery +12V to starter heavy power is not connected, a 20A solenoid will probably take 40A).

  5. #15
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    ahh maybe its to the solenoid on the starter i am thinking, that starter killer circuit basically sits on the ignition wiring, so the start pos doesnt actually do anything, when the central locking is locked & grounded. if ever i have problems, i will have a switch hidden in dash to turn off the ground connection of the remote unit.

    i knew that the full starter power couldnt go through ig switch, just wasnt exactly sure how it got the power :P have looked at fuel cut off. i may go with that idea - but i am thinking thats how my ecu actually immobilises my car atm. - i had a key cut previously when i purchased car - a two quid job - and it appeared to turn over a time or two, but then nothing... also, if my car sits there for say ten mins, even with the correct key in ig and i try to start, it will turn over, then die, as it only primes for starting when key is set to ignition pos once, unlike vauxhalls etc, it doesnt appear to keep the prime pressure up... - fuel drains back to the tank after so long?] - when i first got the car i thought it was maybe a problem, as i know some cars this indicates a leaky fuel line etc, but garage told me kia's r like that.

    ill look into the immobiliser system on my car some, but if the fuel pump doesnt fire without the immobiliser disarming first [chip in key style] there is no point in messin with that

    once again though, thanks!

  6. #16
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    BTW - starter & ignition kill circuits on older cars (without LANs etc) are easy to defeat.

    It's much better earthing the ignition coil- to ground, or better still the ignition sensor outputs (ie, reluctor, hall, optic etc) - though these require different strategies if not "open collector" outputs - ie, like points: they are either grounded else floating.

    A broken power circuit (like starter & ignition) is VERY easy to defeat.
    A shorted system is not so easy - especially if the connections are hidden.

    (The last ignition inhibit system I saw, the installer was stupid enough to make the break at the coil+ terminal. Now that's really dumb!)

  7. #17
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    hi guys.

    SCR came today.



    looks something like this...

    the top "mounting point" conducts to lower central pin, and the two lower pins conduct between each other. but i cant seem to get it to work, so that if i connect the siren, it only conducts when a gate pulse it turned through. how do i do this...?

    never used these before, and its ok thinking i understand the diagram, but practice is different and all.

    which pins are which, and where on my diagram above would they fit?

    Gaoes you said u have the spec sheet for this diode/saw it... where could i get a copy... cheers.

    i also realised after i purchased this thing that i could of


    not sure exactly which way the diode [i believe that is what would be in the red circle] would go, but thats one way to stop the off side grounding when the ground pulse was/is sent through the system via door locks, but still allowing the pulse to be sent from the locking unit -> one way travel

    i see a latching relay 12v/2A in maplins for like 3.51 [web price, but shouldnt be much different instore im sure - if its offline]
    http://www.maplin.co.uk/Module.aspx?ModuleNo=37529

    Q- I want to use this relay for auto signalling on a model railway. Can you supply a diagram of what each pin actually operates within the relay? - D.J.Hurst

    Answer- http://www.maplin.co.uk/Media/PDFs/N38AW.pdf - This is the datasheet for the item.
    unfortunately i dont see the pin assighment in the pdf file, but i only scanned quickily...

    would this be a suitable relay for car use? - note, siren is only 300mA so should be sufficient for grounding siren, yes? 300mA no where need 2000mA [2A] relay can handle at 12v
    - max constant voltage is listed as 18V also, and listed as only requiring 30mA power to latch. and if i assume correctly, it will use NO power unless unlocked, or door open, and even then only breifly, yes?
    - also this relay should only ever be used when central locking is active. meaning engine wont be running, meaning steady 10-12v of battery power.

    but hopefully i wont have to purchase this also, since i already purchased a bunch of 5pin relays off ebay with the scr to perform my operation.

    cheers in advance.

  8. #18
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    Quote Originally Posted by OldSpark View Post
    You could see the12volt's fuel cut off switch using cruise control (page 2, 3rd reply down) for a "self latching" SPST (or any) relay circuit in case SCRs get tricky etc (ie to turn of with DC supply still supplied).
    Not that in that drawing, the two input +12V supplies are usually the same.
    just re-read ur post, and i see your point is not the fuel cut off, but the actual circuit being able to suit my needs also, correct... so i translated that into two possible circuits for myself. top one being basically a replica... lower one, being one i would be using... except in mine, i have not included the diodes, as i see the point in fuel cut off is to stop fuel pump pumping when button is pressed, stopping when released, but kicking in again when relay latches... correct? but i dont see point in circled diode??? im no expert, would like to learn tho, so could u explain it please?

    also, this was actually what i was aiming for myself, a switch being added to coil ground allowing for disarm of siren - if required. still interested in scr since i have it now though. but this relay thing appears VERY CLEVER YET SIMPLE.:P

    coil initially activates because it is grounded via door circuit. when this happens, the coil is being grounded by door circuit AND the central locking starter killer... door closes, starter killer only... when this ground is lost, the relay returns to cold state, ready to set again. - correct?



    edit,,,

    maybe i need a diode on wire connecting coil ground to the relays latching system... so as to prevent the ground pushing back to positive? yes?... at point one...
    and at point 2, also, and after writing this i do believe i understand that the idea is to not fuse the battery, correct? confirmation would be prefered though.

    also, n e recomendations as per resistors / fuses on this circuit?


    edit once again, NOPE, maybe its too simple for me lol, because thinking, the siren would go off every time door opens,,,, as i place the diodes in the wrong place...
    now for diode three....

    im thinking here, do i only need diode three? so as to stop the siren grounding on the door opening, and therefore only when the relay latches, and the starter killer wire is grounded it will sound, removing diode one and two.

    my programmers brain is making something work, and then realising it only works with bugs, and trying to fix the bugs... hell, failing to plan is planning to fail :P can see where it comes from eh. :P

    [additional edit] i now see my origional diagram translated from ur one on 12v is not translated correctly... the diode is after switch, not on joining wire. yes? but i still dont see the reason for that diode... - sorry i have trouble with the whole concept thing :P nice big picture kinda guy :P - hence me drawing crappy coils on the relay etc :P lol sorry


    now i also realise there are diff types of diodes...
    ie: high speed signal diodes [cheap, 100 for 1.76?]
    http://cgi.ebay.co.uk/100-x-1N4148-H...item20aea3526d
    rectifier diodes
    http://cgi.ebay.co.uk/10-x-3A-400V-R...item1c0f429189
    plus others on ebay,
    http://shop.ebay.co.uk/?_from=R40&_t...m38&_nkw=diode

    so what are the difference. there all stop reverse flow? yes? or no?

    thanks...

    and on that note, and with it being almost half three. i think ill head to bed.

    thanks

  9. #19
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    Maybe see The Silicon-Controlled Rectifier (SCR) which is from http://www.allaboutcircuits.com/ - in particular its diagram.....

    (From allaboutcircuits.com with thanks!)

    The great thing about SCRs is that they only need a short +ve pulse on the Gate to turn them on, and then they stay on until the Anode-Cathode current drops to zero (under its holding current).
    The bad thing is - to turn it off - removing its power (ie, a series switch or relay etc) else injecting a voltage pulse on its Anode or Cathode to temporarily zero or reverse their current (etc).


    But I'll re-read this thread later to recap your aim etc.

    In my fig, the diodes stop one power source from feeding the other.

    In it's original form where the two +12V sources are the same (hence one source IS the other source so there is no "feedback" etc), the diodes are in case both switches are closed but the relay contacts haven't yet closed else are faulty - hence the "heavy" load current would go through the "small" switches and melt then. The diodes prevent that.
    Ooops - there is only one switch in that circuit, but same thing.
    The original circuit was to control a pump to keep a tank or sump between 2 levels so the downstream - or right-hand "feedback" link - had a switch too.


    That relay PDF - the pins are shown on the last page, bottom picture "WIRING DIAGRAM".
    Although I do use a latching relay, that's because it is a $5 80A relay that is part of a $20 voltage sensing kit (though I think it only has the one control or coil connection pair). But because of their complex control mechanism, and since my other applications don't really care if their is an extra 200mA (or less) relay load, I avoid them.

  10. #20
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    all right, the reason for using a relay in the first place - avoid burning out coil wiring :P - totally slipped my mind that one. so on my final diagram above, the diode at point three would stay [i think i have drawn arrow right direction on it, but if not flip it round,] and can remove 1 and 2 diode from circuit.

    switches for power are door circuit to activate coil, and starter killer ground will provide main grounding, when unlocked ground is lost, so no more relay lock or ground supplied.

    how long would a 30a automotive relay last connected to a constant positive and door switch, every time door opens, the relay energises. i could also connect a shock sensor to relay coil to ground it temporarily to get initial pulse, but i think i may order a few diodes - from reading some i think that the cheaper 100 for a cpl of quid are for very low voltage n low mA current, so may be better to get a better one - the ten for a cpl of quid as linked, i doubt i will use 10 nm, 100, so wont be any real difference in price yea? also, means i can still install my light dimming system without setting alarm off when doors are locked - as ground wont be able to go through light dimmer making car think doors are open. - its all a matter of knowing what is available [which i dont] and how to use it [which again, i dont - but at least forums like this are here for guidance n to get thinking :P so cheers]

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