diy rpm activated switch.
 

I was reading in the january issue of honda tuning about a guy that made is own switch using a 30 amp relay. I thought about it and it could possibly be done by using resistors to prevent the relay from closing until a certain rpm (the tach signal would have resistors between it and the relay). Has anybody tried this or does anyone have any ideas or input? What happened to shortyz list of resitors compared to the rpm the correspond to on the autometer shift light?

I'll try this and let you all know how it turns out. testing will be done by the end of february because I'm lazy like that.

Re:diy rpm activated switch.
 

Kyle thats a good question. I'd be interested in knwing how to build an rpm switch myself for a future swap. ;)

Re:diy rpm activated switch.
 

I just asked this same q in another post, but somewhat on topic, do you know what kind of signal the tach gets? I wanted to make a gauge, but someone told me it gets voltage pluses, whatever that means :-\ whereas I assumed it gets a steady signal that rises with rpm. If it gets a different sort of signal (sounds almost like a/c but all in the positive??? I got no idea what voltage pluses are) seems like it would be hard to implement this.

Re:diy rpm activated switch.
 

OKay, I'll try ot make it short and simple. RPM = Revolution Per Minute, which refers to the number of times the crankshaft turns in one minute. RPM signals are normally taken from the ignition circuit that controls the ignition coil. The ignition coil fires every time the ignitor tells it to. This on/off/on/off firing of the coil produces a spark for each time the coil is switched off (I can explain further on the "off" if you like, but you'll need to understand what "magnetic lines of flux" are all about). A fixed number of sparks are created for each revolution of the crank. As RPM increases this on/off/on thing happens quicker and quicker, because the coil is still must generate the same number of sparks per revolution, even if the revolutions are getting quicker due to rising RPM. When you tap into the coil control signal, you see the on/off/on/off cycle as 12V/0V/12V/0V. This actually occurs so quickly, that you cannot see it with a voltmeter, it takes a scope. Each 12V portion is called a positive pulse. The Tachometer, reads the number of pulses per minute, and converts this to an RPM value.

Whew!

Re:diy rpm activated switch.
 

well, i'm no EE, but a 2907 freq>voltage converter and an lm311 comparator should do what you want it to. a 339 quad comparator could be used if you wanted to activate more than 1 thing..

here's a schematic i drawed up..
http://www.imagestation.com/picture/...f/f9fb4be0.jpg

if you want a full sized pic, PM me and i'll email it to you.. imagestation seems to like shrinking my ---- lately..

this is for a positive response circuit, meaning it turns on when at and above a certain rpm level. if you want a negative response circuit, meaning if you want the switch to be on below a certain rpm level and turn off when you reach a set rpm, all you have to do is switch pins 2 and 3 on the 311 comparator.

hope this helps.. EE's, if i missed something, please correct it.

Re:diy rpm activated switch.
 

scarecrowx is a pimp. e-mail me the bigger picture please, I like going into radioshack and telling them they can't help me. Honda16hb@hotmail.com

Re:diy rpm activated switch.
 

I got the schematic, I just need to build this now, once it's done I'll borrow a camera since I can't find mine and put some picts up.

Re:diy rpm activated switch.
 

IF you can set it to turn on and off at certain RPM... you could use it to controll your nitrous to spool up your TURbo's ;D JUst put it in a fancy little box.... maybe a LED to let you know its activated.. and your good to go

Re:diy rpm activated switch.
 

pm ;D me vigorhn
thanks

Re:diy rpm activated switch.
 

good call on the LED.

it could also control ITB and VTEC (honda) or TVIS (toyota).

if anyone's wondering, ITB and TVIS are variable intake runner systems by each of those manufacturers. at least on the toyota, people saw about 10 ft-lb gains in low to mid range by holding the valves closed longer than stock.

for the ITB and TVIS controls though, they would have to be negative response circuits. the ECU opens the shorter/bigger runners by ungrounding the actuator solenoid.

Re:diy rpm activated switch.
 

Would there be interest in pre-made circuit boards? I could very easily get 20 or 30 boards made, probably $5-8/board for the BARE board - you'd have to solder it together yourself.

if there is interest, post here or email me.

Re:diy rpm activated switch.
 

i would be down for 3

Re:diy rpm activated switch.
 

couldn't this circuit (less the LM2907) be adapted for use as an electronic boost controller? i mean run the MAP signal (with conditioning) and an adjustable reference voltage to the comparator - then have the output cycle a vac solonoid on waste gate. a simple panel meter (based on the LM3914 like the diy a/f gauge perhaps?) could be used to check your setting and monitor boost.
i figure it could probably be put together for under $30, and would be a nice step up from the bearing-spring MBCs, without spending $200+ on a commercial unit.
i guess you could take it another step and feed the RPM switch circuit with your speed pulser signal instead, then have the output switch on a higher boost level above a certain speed - traction control.

Re:diy rpm activated switch.
 

Yeah blundar I too would be interested in picking up a board if you can get them.

Re:diy rpm activated switch.
 

apparantly, you and i think a lot alike. i already have schematics drawn for everything you're talking about here...

i bought a group of 10 solenoid valves too, but they may not be ideally suited for boost control. i've already started work on the boost controller you're talking about though...

Re:diy rpm activated switch.
 

sweet... i guess you're planning on selling them, so sharing the schematic is out of the question ;). i had envisioned using a '88-91 civic purge solonoid (what i had on hand really) - it normally switches a control port between manifold vac and atmospheric pressure, so waste gate response would be quicker than, say, a on/off valve and a bleed orifice.

Re:diy rpm activated switch.
 

Saab, volvo and Ford RS turbos used Amal valves, those just switch the wastegate between a boost line and an atmospheric line which is vented into the air intake.

Re:diy rpm activated switch.
 

I could possibly get 5 or more of those boards, let me know if they happen. pre made circuit boards would help, I have all kinds of crazy stuff going on on my a/f gauge pc board.

I Know a lot of years have passed... but does anyone got this DIY? Any pics or develop?

Chears!