LED Outputs mod required ?

[gboezio]

Hi, I'm building a 3.0 DIY board and I have a few things that confuse me :

1 : In the spare outputs section, it says that mods are required to drive relays, Can the NPN transistor of D15 be used as a relay driver as without mods, or it require extra components or a stronger NPN, will solder a diode on the relay anyway. I'm running out of room on the proto board due to to TC4427 ignition mod and spare inputs.

2 : sounds weird but, can a 5 amps fan be PWM driven by Inj2 ?? Reason is it's a single cyl race engine and Inj2 is not needed and electrical power in on a budget, it was this way from factory on a TRX450r CDI box, I'm just afraid of flyback current, noise and other things that I have overlooked.

3 : Answered #3 while writing it lol

[jsmcortina]

1. The transistors should be ok for a typical small relay, but be sure to add the flyback diode across the relay coil.
2. I think that the injector circuit could drive a fan, but I'd be concerned that the flyback energy would likely damage the board. Use a relay for safety.

James

[gboezio]

Thanks James
I have wired a relay and used a led out pin

Another question that require full knowledge of the system :

I have a normally open kill switch, means ground conductivity kills the engine.
Reliability is king in this build

1 : Of course I could use a relay to reverse the KS operation, but I'm running out of room in the vibration insulated box, but I will have to do this if I can't find another descent solution
2 : best option to me would be an generic input that would cut ignition, but I can't find something that does it, maybe a rev limiter set to 0 ??
3 : Grounding the TC4427 Spark output, with the 15 Ohms resistor, maybe will flow 1/3 amp, shouldn't blow the fuse or anything else ??
4 : grounding the Cam 1GT101 output
5 : grounding the Crank VR signal....yikes...high volts in a wet/muddy switch

Thanks for input...and output !!

[billr]

An NO switch isn't as "fail safe" as an NC, in my opinion. A broken wire/connection means you have no kill available. Why not put an NO switch in series with the power feed for the pump and injector? Ignition kill is good... but injector kill is better. Engines can keep running a bit with no spark by "dieseling", especially if they have been running hard and some hot-spots are in the combustion chamber.

[gboezio]

Thanks Bill, The reason I like the NO kill switch is that if it fails the engine will keep running, the kill switch is mainly to meet regulations, I have never seen one save the crowd , but too many ruining races, it could be ripped off if needed.
The fuel pump relay is a good candidate, driving both ignition coil, injector and fuel pump. It would be great to shut it down internall from the MS3., so the fan could still run and datalog file be continous.