flip/flop latch for ignition + kill sw

I'm in Melbourne. Presently in the Greensborough area. But I suggest you HALT and reconsider. If you are adding the GND to prevent staring, there is NO cutting involved. And you do NOT touch the existing kill switch circuit. And why do you want to open the existing battery supply to elsewhere? (And when?) I have only been discussing an engine kill -cum- start disable function. I may have mentioned "interrupts" or "isolation switches" but that has only been to point out the difference between an ignition kill and "safety" type battery isolation circuits, and to mock those that combine the 2 into ONE switch without understanding the issues and hazards, or to point out the risks with interruption or breaking circuits. I'm happy to endorse a staring or ign immobiliser that uses the NO contact of an IGN +12V actuated relay else the NC contact of a de-energised relay (when IGN is off, and until the IGN with the "unlocker" energises that relay). I am NOT endorsing nor mean to suggest any form of circuit or relay insertion - ie, no cutting of existing wires etc. (Nor have I ever done that for critical circuits except under specific conditions.) BTW - that's what an SPDT relay is - "change-over" contacts. 87 is NO; 87a is NC (with respect to the "common" 30). And many buy only SPDT relays since that can be used as mere SPST relays. (Hence one part or spare suits both SPST & SPDT applications.)

Hey thanks for pointing out the obvious on the relays. I suppose I could then go for a DPDT to break the coil ground and the other to open the fused +12v supply to the rest of the bike. I would use the other relay to allow power from the battery to supply current to the lights, tachometer etc...like an acc.  so when the IGN is off, nothing will work, engine or electrics, e.g. light, horn etc.. do you think that is a bad idea?

About the wiring, I think I was paraphrasing you. I would keep the KILL swich between the coil and GND. I would also tap in another wire in parallel from the coil to GND through one of the relay poles.

The other relays were to support the idea of reducing load and isolating devices with their own fused supplies, i.e. headlights on their own fused line a USB connector on its own fuse and possibly through a switch.

You still do not understand - there is NO COIL GROUND to or kill-switch GND to break. An Ignition Coil has no hard ground connection. It has +12V connection from the IGN switch (or IGN relay) thru the kill switch to the coil+ and the HT lead to the splugs (else dizzy). Its 3rd connection is from the points or ignitor which connect the IgCoil to GND - that is its ONLY connection to GND. (To GND charges the coil, breaking GND fires it.) The only difference with most CDIs is that there is no IgCoil charging time - the "points" cause a capacitor to discharge into the IgCoil. (The IgCoil acts as a pulse transformer. It is not pre-charged as with traditional/normal inductive/Kettering type ignitions.) But in both types, there is no GND to any kill switch to interrupt... So if you are talking about GND connections, that has nothing to do with the bike's kill switch, so keep the kill switch out of it.    And if you are talking about breaking the +12V thru the bike's kill switch or breaking the coil- trigger path, then I won't help any further because of the risks I outlined earlier.    If you do have a system that does not operate in accordance with the above, then explain how it is wired and how it works and I'll take it from there.

Hi mate, Sorry, I don’t think I have been clear in my posts. I realise that there shouldn’t be a connection from the coil to GND (for normal operation). Now on my motorcycle, there are two ways to kill the engine, the KILL switch which creates a connection from the coil to GND and the ignition switch which does the same (via a parallel connection) when it is in the OFF position. You can reference the following wiring diagram: http://www.suzuki2strokes.com/forum/viewtopic.php?f=29&t=4743&start=8 The ignition switch also creates a connection to supply fused +12v from the battery to the motorcycle electrics when it the accessory or ON position. So all I want to do, is find a way to substitute the functionality described above with an "RFID switch" and I am happy to skip the accessory mode, and just have ON and OFF. Now using a latch similar to hotwaterwizard along with the RFID module, I have my "RFID switch". The next challenge was how to perform the two ignition key switch steps. a) Remove the GDN connection to the coil (i.e. Ignition off) b) Allow fused 12+ to provide current to the electrics. Based on our discussion I could do this with a DPDT relay or two SPDT relays, let’s assume I am using two: Relay 1. Pin 30 to GND, Pin 87A connected to coil, Pin 87 not connected Relay 2. Pin 30 to +12v fused out from battery, Pin87A not connected, Pin 87 connected to motorcycle +12v supply. My questions a) Would Relay 1 be a safe addition to the circuit? I was worried that it might detach due to vibration. b) Is the latch in hotwaterwizards design good for this application, should I add any other protection (diodes, resistors)? This relay circuit would also be subject to mechanical failure. But then again, what kind of relays are used by modern vehicles and motorcycles? Hope I have been a bit clearer. Thanks again for your time.

Ok, so you have my step-thru's type of system. I would not have expected that on a normal bike. Your relay connections above are fine; both relays energised by IGN and the RFID. Relay bounce has no effect on the points/ign short. I'm not sure that the +12V relay is needed nor desirable. Ign is shorted until the RFID is used, and that should only be with the IGN key. So why cut the +12V unless you want the RFID to bypass the IGN switch which means the RFID receiver is draining the battery? I figure IGN on which powers the receiver. The RFID then pulses the latch to energise the NC spark shorting relay.    I reckon I'd use my single relay latching circuit - maybe by using a DPDT relay to do both (latching and shorting). IGN off kills the +12V to the relay coil, hence breaking the latch and reapplying the short until IGN-on and RFID repeats. But I am a bit on the tired side...

oldspark wrote: I'm not sure that the +12V relay is needed nor desirable. Ign is shorted until the RFID is used, and that should only be with the IGN key. So why cut the +12V unless you want the RFID to bypass the IGN switch which means the RFID receiver is draining the battery?

So I was thinking it would be safer to have my electrics OFF when I am not arround. Stops people truning on my lights etc...or letting them think they could start the bike.  I Thought about having a single connection off the battery connected to a switch, either dedicated or off the front brake that will activate a timer to provide power to the RFID antenna. Thinking a simple push button switch would be best.

oldspark wrote: I figure IGN on which powers the receiver. The RFID then pulses the latch to energise the NC spark shorting relay. I reckon I'd use my single relay latching circuit - maybe by using a DPDT relay to do both (latching and shorting). IGN off kills the +12V to the relay coil, hence breaking the latch and reapplying the short until IGN-on and RFID repeats.

Cool, using one DPDT relay makes the most sense, I just thought I would be best to use a "high power" relay to run the +12v BAT to the rest of the bike. I have upgraded my alternator and will be putting some serious lights on the bike.

So the idea was that I could use the RFID reader to turn off the IGN, this is why I was looking at the "flip/flop" relay design. You're circuit is a permanent latch held until supply voltage is lost, additional pulses from the RFID circuit will not alter the state.

I am in two minds about doing this just yet as I have spent the best part of 4 months re-building this bike from the ground up...so I am sure I will have other issues to deal with...I just would have liked to do away with the key and have a cleaner looking bike...

Thanks again for your thoughts.

So my take away is that the use of "automotive" relays should be fine and failures  from viabration should not be a concern, I am not doing stunt riding or racing.  The circuit provided by yourself will work as will hotwaterwizard's latch. I guess the only thing would be to put a diode accross the coil.

But your electrics are off when you are not around the bike. Removal of the IgKey cuts power. Without any IgKey we have that issue if the relay bounces or fails, or the battery/supply goes too low.     Also that the RFID is always powered, but that depends on its drain versus battery capacity and desired battery life. And being stranded if you have a flat battery - unless a push start and a permanent magnet type alternator else enough residual magnetism in a wound rotor. [ PS - Sorry - I am repeating earlier stuff that you have acknowledged. ] You are quite right about the DPDT rating - high current for the alternator & lights. I was assuming a 30A relay which should be more than enough for your alternator, though I also assumed that since the kill switch was a grounding type, the alternator was a typical "matching" dual-output - one dedicated to lights and the other for the battery and bike (ign, instruments, horn, flashers, stop, etc) and probably a stator = permanent magnet rotor type. I wouldn't think a diode across relay coils would be necessary, but better safe than sorry.