Electronics question
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Electronics question
My problem comes from using the factory ECU harness for the MS install. I have a ECU connector from a dead ECU and have used that to make an adapter loom from between the stock loom and the MS DB37. Where I ran into trouble was with the circuitry for the main power relay. The relay's coil is switched on both the positive AND negative side, the positive through the ignition switch, and the negative side through the ECU. When the ECU is removed then that part of the circuit is removed, and the main relay does not turn on. So I have to come up with some way of switching the relay's coil to ground, using a +12v input.
I did some googling and read some on using transistors as a switch. Like this:
Now if my understanding is correct R1 is connected to the base, the emitted goes to GND and the relay coil is connected to the collector. When a voltage is put to the base that allows current to flow from the collector to the emitter. The relay coil already has +12v on one side so it's effectively grounding the other side.
Re: Electronics question
If you are switching a few amps or more you may want to add a diode (eg. 1N4004) across the relay to protect the transistor from an emf spike when the relay is switched off. Connect the cathode to the positive (+12V) side of the relay and the anode to the transistor side.
Here's a reference if a picture helps http://en.wikipedia.org/wiki/Flyback_diode
Re: Electronics question
If that is correct, then why not just ground the ground side and rely on the ignition switch to control the relay? Thats how a main relay would be done in a normal MS install.
Otherwise I agree with long283.
Cheers
Daniel.
LS3 powered Race boat with MS3pro and GPIO.
MS2 on a 22r in a Hilux (mates car).
MS2extra on a turbo EF Falcon (brothers car).
Toyota Supra 1jz MS2extra, COP.
13B Turbo MS2extra.
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Re: Electronics question
Actually my description is not quite right because I tried that and even with the ignition off when I ground the -ve side of the relay coil it turns on, so the relay must have constant 12v to it.devojet wrote:Let me know if I have read your post correctly. The 12V side of the relay is switched from the ingition, and the ground side is switched through the Factory ecu. I assume this relay feeds power to the MS, injectors coils etc.
If that is correct, then why not just ground the ground side and rely on the ignition switch to control the relay? Thats how a main relay would be done in a normal MS install.
Otherwise I agree with long283.
Cheers
Daniel.
The EMF spike was going to be my next question, thanks for mentioning that!!!
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Re: Electronics question
I'll set this up on a proto board and see how it goes. Thanks again!
Re: Electronics question
That updated diagram is correct.
Another way to protect the transistor is to use a ~22V zener. Connect the cathode to the transistor on the negative side of the coil and the anode to ground. Similar to the wiring in the MS for the fuel-pump, Idle-air Solenoid circuits.
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Re: Electronics question
Right?
Re: Electronics question
Cheers
Daniel.
LS3 powered Race boat with MS3pro and GPIO.
MS2 on a 22r in a Hilux (mates car).
MS2extra on a turbo EF Falcon (brothers car).
Toyota Supra 1jz MS2extra, COP.
13B Turbo MS2extra.
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- Helpful Squirter
- Posts: 61
- Joined: Fri Mar 11, 2005 10:30 pm
- Location: Qld, Australia
Re: Electronics question
EDIT: Added datasheet as attachment
- Attachments
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- KSP2222A.pdf
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Re: Electronics question
Someone please correct me if I'm wrong.