relay question

Wiring best practices and loom building technique
iceman_n
Posts: 141
Joined: Mon Jan 16, 2012 1:39 pm
ECU Model: S40 Pro
Firmware Version: 58

relay question

Post by iceman_n »

hello
i have the above issue and i dont know how to wire it up

facts :

key position 1 click - 12v feed (when cranking it stops 12v feed)

key position 2 click = cranking position - 12v feed (when in non cranking position (1click) it stops 12v feed)

so when had wire a normal relay i had 12v feed on 1 click position but not at cranking position so dta was off

any ideas how can i wire a sophisticated wiring relay system (even using 2-3, or normal open/close relays etc)

thanks in advance
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: relay question

Post by Rob Stevens »

Just to clarify you have 3 rotary positions, or is something else?
position 0 = Off
Position 1 = On*
Position 2 = Sprung position for starter *but looses 12v when in position 2

Have you tried all the connectors on the switch? if its some sort of toggle switch it sounds specified wrong, just get the right one.

Or keep switch one (could be useful for cranking engine without power for oil prime?) and add a button for the starter.

I wouldn't introduce a load of relays, just more fault points.

Something like this switch would do what I think you are trying to do https://uk.rs-online.com/web/p/toggle-switches/7831028/
iceman_n
Posts: 141
Joined: Mon Jan 16, 2012 1:39 pm
ECU Model: S40 Pro
Firmware Version: 58

Re: relay question

Post by iceman_n »

Rob Stevens wrote:Just to clarify you have 3 rotary positions, or is something else?
position 0 = Off
Position 1 = On*
Position 2 = Sprung position for starter *but looses 12v when in position 2

Have you tried all the connectors on the switch? if its some sort of toggle switch it sounds specified wrong, just get the right one.

Or keep switch one (could be useful for cranking engine without power for oil prime?) and add a button for the starter.

I wouldn't introduce a load of relays, just more fault points.

Something like this switch would do what I think you are trying to do https://uk.rs-online.com/web/p/toggle-switches/7831028/
correct yes...i have test all the wires from the switch with voltage meter so is as i say above, i have thought the external switch too but i wanted to try with relays only

i found a solution after many circuit drawer on the paper...the only one that works in all cases is with 2 change over relays, my only hasitation is if the voltage move so fast that will keep DTA active from position 1 to position 2 and back over again, also i found a solution with 1 change over relay, working backwards and 1 normal one relay...looks simpler and faster

all the other solution i found with relays are simpler but DTA will not shut off when key at position 0
Last edited by iceman_n on Sat Feb 01, 2020 1:00 pm, edited 1 time in total.
Rob Stevens
Posts: 1247
Joined: Thu Jul 28, 2011 4:10 am
ECU Model: S100 Pro
Distributor: None-Coil On Plug :)

Re: relay question

Post by Rob Stevens »

Just buy the right switch? !!!
I doubt you can make it work correctly or reliably without pulsing the DTA
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: relay question

Post by stevieturbo »

Sure it isnt a faulty switch ?

An ignition switch that kills power to everything that needs power during cranking....is a little odd lol. Or just faulty.
iceman_n
Posts: 141
Joined: Mon Jan 16, 2012 1:39 pm
ECU Model: S40 Pro
Firmware Version: 58

Re: relay question

Post by iceman_n »

thats the wiring diagram if it helps

https://pasteboard.co/ISI3buu.jpg
CraigPowers
Posts: 9
Joined: Sun Jan 26, 2020 10:18 am
ECU Model: S80 Pro

Re: relay question

Post by CraigPowers »

I agree that the switch sounds very odd or faulty. Better to replace it, or get one that suits the application

Instead of relays you can use a power diode to feed the ECU from the cranking switch position. Therefore the ECU will be fed from one of the two switch positions, uninterrupted 12v.
It needs to be a power diode because it is feeding the fuel pump etc. The blocking diode stops the starter being permanently engaged.
(I use a similar diode arrangement on my fuel pump and water pump circuit. Water pump always runs when pump running, but can be overridden by a switch when ECU is off)


normal 12v feed o-----------|---------to ECU
|
-----
^ diode
|
cranking 12v o-----------|----------- to starter solenoid
Last edited by CraigPowers on Sat Feb 01, 2020 2:48 pm, edited 1 time in total.
CraigPowers
Posts: 9
Joined: Sun Jan 26, 2020 10:18 am
ECU Model: S80 Pro

Re: relay question

Post by CraigPowers »

My diagram didn't post correctly because it supressed the spaces that I had inserted, but the diode is strapped from cranking 12v to normal 12v.

I've attempted to upload a sketch (attached)
Attachments
ECU switch diode.jpg
iceman_n
Posts: 141
Joined: Mon Jan 16, 2012 1:39 pm
ECU Model: S40 Pro
Firmware Version: 58

Re: relay question

Post by iceman_n »

https://pasteboard.co/ISIBEty.jpg

Can i go with something like above ? I feel safer with diode to control the low side of the relay and not directly the ecu
CraigPowers
Posts: 9
Joined: Sun Jan 26, 2020 10:18 am
ECU Model: S80 Pro

Re: relay question

Post by CraigPowers »

You should be able to get away with it. The diode will drop 0.7v so you will have the normal cranking losses as well as the extra 0.7v but hopefully the ECU will ride through that without complaining. You will need a diode that can power the fuel pump and any other ancillaries.

The best alternative is a switch that doesn't interrupt the normal 12v feed whilst cranking, as Stevieturbe says. My solution is a fudge.

Edit: Just seen your relay diagram. Yes, that would be OK because the ECU won't see the diode volt drop.
Post Reply