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Solid state relais/triac

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New Member

I'm building a rpm limitter for a car engine.
I usa for it a PIC cpu but that's not the problem.

the method i want to use to stop de engine is very simpel, i want to cut of the power supplied to the "Bobine" = "ignition coil" the voltage is a car voltage (engine off 12volts on it is 14volts ) the amps are high 4ams running at 1200rpm/min (don't know yet if it increases when there are more rpms.

OK to the point when running at 5500rpm/min i cant's use a normal mechanical relay because it is to slow. and when pussing the pedal to the limit the switching frequency would be very high..

soow i need to build a solid state relais my question is
how can i build one. and wich components i need.

basicly it should be something like this

-- i have steer power of 5v and 8v and (car voltage..12-14)
-- 4amps min. i want something like 12amps.
-- fast switching <1ms???

i was thing using a triac but i dont know if it usefull in this case.
soow please help.



New Member
solid state

i already buyed a SHARP S216S12 (solid state relais).

buy i f**ck*d it up whit to much power to the led :evil: .

i remember when i was measuring at the 2 pins i measuerad a
resistence of 800ohms. i was supplieing a 12volt and a 650ohms in seri whit it.

a normal relais (mechanical) doesnt has any resistancy i like that more than 800ohms.

hope somebody can help



New Member
Can we assume that this is an older type engine with a simple ignition system? If so it would be better to short the points to cut the engine rather than to remove 12V from the coil. However, you have to consider that when your rev limiter cuts out the ignition the engine is still turning fast and is still sucking in gas/air mixture which now does not get ignited and accumulates in the muffler. As soon as your ignition cuts back in you will get a big bang as that gas ignites in the muffler - not the best idea.
Rather than tinkering with the ignition you would be better off reducing the throttle somehow to limit the revs, perhaps some solenoid to do that to the linkage.
I would not want to drive a car where the ingition keeps cutting in and out, could be very dangerous if one was in the process of overtaking.


New Member
its ainjection car.

hello listen good..!!

when you do it very fast..!!!

and for short periods there its'n much mixture in the muffler.. and the sound what it produces is very good en like normal running.

soow your story doesn't apply in my case give me a good idea instead of triing to pass me all de thinking job again. :(

the reason i doen't cut off the injection spray is that i would heat my engine a lot since the engine fuel also takes away heat from the valve's ect... 8) :shock:



let everybody does his job let the electronics for the electronics en the mechanical for the mechanicals... :lol:


New Member

thanku very much
i'm ganno dive in the world of the fets and trying to apply him..

hopes that it will work out..

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