http://www.the12volt.com/relays/page2.asp#psk
basicaly im using the passive starter kill from that link when i remove my tired knackered alarm/imobiliser from the mini
however there was a bi-coloured LED in there that is normaly red but green after imobiliser button had been pressed an i was wondering if anyone had any ideas on how to integrate this into the homemade imobiliser
anyone?
Is the LED common ground or common supply?
tis i bi-colour LED so it works either way, current flowing one way makes it one colour, current flowing the other way makes it the other colour
Only two pins? The ones I’ve used have three and to be honest that would be far easier to use! On your circuit and looking at the latch relay, pin 87A is live with the immobiliser active and pin 87 live with the immobiliser inactive. If you were using a three leg bi-colour relay you could easily wire it into that but I don’t know whether your LED will work properly with a floating earth as it would be in this circuit or indeed how much effect it would have on the immobiliser. You could do the maths and work it out, or just try it.
first i’v heard of a 3 legged LED, will speak to my friend who works in maplins, if there is a 3 legged one then all is good and it saves me having to use 3 extra relays for the sake of a LED, as i did figure it out but as said for the sake of a LED its not worth 3 extra relays
oh and power is only supplied to pins 30, 87 and 87a once the relays have latched…so until the push button is pressed theres no voltage going in or out of the output pins
using the idea of the 3 pin bi LED is to have a 3rd relay with a constant 12V going to 30 with the RED + leg going to 87a and the green leg going to 87 with pin 85 going to the live output of the other relays (so that its green when immobiliser button pushed)
thats a simulation mock up of the relay circuit, SW2 is the ignition, SW3 is the 3rd position (starter) of ignition and SW1 is the push button, as you can see (orange means + voltage green means grounded) the outputs for the relays have no power when ignition turned off so cannot power the LED that way, did try puttin pin 30 of the right most relay to a permanent + however the idea is when u turn off and remove ignition keys the circuit resets and immobiliser re-activates however with a permanent feed the circuit did not reset
PLEASE NOTE THAT THE TWO PINS AT THE TOP OF THE LEFT MOST RELAY (when compared to relay diagram on website) ARE SWAPPED AROUND SO THAT SW3 GOES TO PIN 30 OF RELAY AND PIN 85 IS JOINED TO 85 OR THE RIGHT MOST RELAY
apolagies for the capitals but wnated to make sure you notcied the mistake in diagram even though its only a small one it still works exactly the same
Ah, yes I’d overlooked that the supply was only there with the ignition on. Foolishness.
I’m pretty sure there is a way to do this with ballast resistors rather than an extra relay. You have to use resistors to play with the voltage across the bi-colour LED so that it will see a drop in the right direction to make it light red until the immobiliser is switched off at which point the voltage gradiant is reversed. The trick though is that the LED doesn’t ever actually see a proper zero volt ground, because it doesn’t have to. The 2 pin bi-colour is probably going to end up being best to use in this way. Right now I can’t think exactly where to place it in the circuit but I’m off out at the moment so I’ll give it some thought later.
cheers dan, as far as i know though current has to flow one way for one colour and the other way for the other colour
It does indeed but if you play with resistances you can change things a bit. You have a total range of 12 volts (I know it’s more than that in reality but we’ll say 12 for simplicity) to play with between the high and low sides of the circuit. You have a relay that changes over between zero and 12v (well at the moment it changes from open circuit to 12v) when the immobiliser cuts in. So you use a resistor to make one side of the LED 6v (assuming this LED will light at 6, if it won’t you’ll have to find one that will). The other side of the LED will switch from 0 to 12 meaning the average accross the LED will change from 6v negative to 6v positive when the relay switches. I think you’ll have to alter the arrangement of the latch relay so that it changes over from ground to positive at the output rather than from open circuit to positive, although you’ll have to check that this won’t result in a short. As I said I’ll give it some thought.
i semi-understand what your on about, if theres any chance you could maybe draw what your refering to that would be a great help
im having troubles figuring out a way of turnin the open circuit part of the relay into a ground without compramising the circuit
but saying that the 3 legged LED would save an incredible amount of fuss by simply adding a 3rd relay and i could also incorporate the 3rd relay to cut out power to the coil, admitedly this means the relay will be energised the entire time the car is running so i have no idea of this is safe as i dont know how much current to coil draws
bump
had any moments of eureka yet dan
Hi, yeah sorry I forgot about this for a couple of days. I had a couple of doors to hang at home. I think I’ve worked it out, the latch relay will chage-over from ground to 12v to drive the immobiliser relay and the LED but a diode will prevent the ignition supply grounding. I can’t work out what size resistor is needed as a ballast though, do you happen to know the number of the LED? I’ll do a drawing then I’ll ask DK Lawson to have a look, he’s a bit of an electronics genius and I think he’ll be able to solve it.
cannot say i do im afriad…could you do a rough paint drawing of what you mean though?
dan?
Sorry, forgot again. My memory is terrible. I’ll contact DK tonight.
can ya do me a rough diagram of what your talking about? using the image i provided as a starting point?
Really gotta go now but I’ll get one up here in the morning.
Ok here’s a very rough sketch. This should work but it depends on the spec of the LED. It should be safe (make sure it’s all on fused circuits where appropriate though). See what DK thinks.
And I know it’s not quite morning any more, sorry!
