NickJ Posted September 3, 2017 Share Posted September 3, 2017 How well do relays last when switching points, would a solidstate option be slightly better here? The method I was looking into was cutting every 3/5/7 spark to ensure the cut cylinder is shared around, with the arduino you could bracket the amount of cut in line with the rate of rise. I've been using a LM2907 for getting digital rpm information to my datalogger, works really well Quote Link to comment Share on other sites More sharing options...
chris r Posted September 3, 2017 Share Posted September 3, 2017 My thoughts too re the relay. Solid state or a higher power transistor might be a better option. Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted September 3, 2017 Share Posted September 3, 2017 to all those people saying that rev limiters on a carby engine is a bad idea/wont work/will suck. i can garantee you, you are wrong and its great fun, i had my bike carbed 18r in the corona running a megasquirt for ignition and this allowed adjustable two step. i only have a couple of average videos for your enjoyment but here you go (in this one my mate in the drivers seat was not holding the the throttle flat, which is why it kinda revs weird) this one actually shows it being used in a drag application (the car is still slow though) such lols in an old car with launch control 2 Quote Link to comment Share on other sites More sharing options...
Benno Posted September 3, 2017 Author Share Posted September 3, 2017 42 minutes ago, NickJ said: How well do relays last when switching points, would a solidstate option be slightly better here? The method I was looking into was cutting every 3/5/7 spark to ensure the cut cylinder is shared around, with the arduino you could bracket the amount of cut in line with the rate of rise. I've been using a LM2907 for getting digital rpm information to my datalogger, works really well I was also a bit concerned about the life of the relay, but then realised I (probably) won't actually be revving it to hit the limiter that often. If I was, the relay probably wouldn't be the first point of failure haha. Under normal use the relay will just be in the normally closed position not actually switching anything. Certainly something to think about in the future though. Quote Link to comment Share on other sites More sharing options...
chris r Posted September 3, 2017 Share Posted September 3, 2017 18 minutes ago, Fliboi said: to all those people saying that rev limiters on a carby engine is a bad idea/wont work/will suck. i can garantee you, you are wrong and its great fun, i had my bike carbed 18r in the corona running a megasquirt for ignition and this allowed adjustable two step. i only have a couple of average videos for your enjoyment but here you go (in this one my mate in the drivers seat was not holding the the throttle flat, which is why it kinda revs weird) this one actually shows it being used in a drag application (the car is still slow though) such lols in an old car with launch control The difference is you are using megasquirt for the ignition trigger not points. Quote Link to comment Share on other sites More sharing options...
NickJ Posted September 3, 2017 Share Posted September 3, 2017 27 minutes ago, Ben_10 said: I was also a bit concerned about the life of the relay, but then realised I (probably) won't actually be revving it to hit the limiter that often. If I was, the relay probably wouldn't be the first point of failure haha. Under normal use the relay will just be in the normally closed position not actually switching anything. Certainly something to think about in the future though. I'd be worried about the relay fusing shut, then failing to operate when needed, there are a number of dedicated ignition transistors about, would be worth looking at their suitability. Quote Link to comment Share on other sites More sharing options...
chris r Posted September 3, 2017 Share Posted September 3, 2017 it shouldn't. fuse shut, they are rated to 20 or 30 amps. I was wondering about the delay with the coil energizing and how it'd cope with being switched quickly It might dirty the contacts pretty quickly but at the end of the day it is cheap and easy enough to try Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted September 3, 2017 Share Posted September 3, 2017 4 hours ago, chris r said: The difference is you are using megasquirt for the ignition trigger not points. Actually my enter megasquirt ecu was triggered from the points at that point in time..... So yeah.. 1 Quote Link to comment Share on other sites More sharing options...
BlownCorona Posted September 3, 2017 Share Posted September 3, 2017 Would using a power transistor/ignitor work better than a relay? That is their designed purpose after all Quote Link to comment Share on other sites More sharing options...
chris r Posted September 3, 2017 Share Posted September 3, 2017 Uuh 1 hour ago, Fliboi said: Actually my enter megasquirt ecu was triggered from the points at that point in time..... So yeah.. But the megasquirt controlled spark yes? So in your case it goes points - - >megasquirt -->coil correct? So when the megasquirt does rev limit itself there is no change to the input signal. Carb it goes points >coil and the revlimiter is in parallel with the points essentially. So when you reach the set rpm it triggers the coil negative at a x frequency. The coil negative is also connected to the points And the input to the reverse limiter. And because the rev limiter is putting out x signal not the actual rpm it goes mental and is not steady. The theory with using the relay is to "change " the coil negative from the points to the rev limiter so you do not back feed the signal. A relay is cheap enough to test if it'll work. If it does great go for it. Quote Link to comment Share on other sites More sharing options...
chris r Posted September 3, 2017 Share Posted September 3, 2017 Anyway back on topic @Ben_10jaycar do a cheap shift light kit which includes a schematic for a ignition cut circuit. I made it (the ignition cut) up on a bit of verro board so If you are ok with a soldering iron that could be a option. Edit I can't find it on their website but I have the Destructions somewhere and am happy to scan if needed Quote Link to comment Share on other sites More sharing options...
Benno Posted September 24, 2017 Author Share Posted September 24, 2017 Managed to get my first prototype working. https://youtu.be/Z-gVERQfiXk I've got an Arduino set up which is reading the RPM and switching the relay when the RPM exceeds the limit. I haven't looked at the 2-strp functionality just yet. Kinda hard to hear over the fan, but it limits at about 5000 in the video. I will get an Arduino nano and sort out a voltage regulator circuit and should be good to go hopefully. 5 Quote Link to comment Share on other sites More sharing options...
peteretep Posted September 24, 2017 Share Posted September 24, 2017 Awesome man! You now need to show us all directions, components and how it all works in extreme detail 2 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted September 24, 2017 Share Posted September 24, 2017 http://nz.rs-online.com/web/p/products/5339331/ I have just ordered some of these. General consensus seems to be that they are a far more reliable (and smaller, if it matters) option than the adjustable chinese regulators. To be fair- I'm unsure how easy they are to use and if they are stand alone regulators or need to be part of a larger system 1 Quote Link to comment Share on other sites More sharing options...
chris r Posted September 24, 2017 Share Posted September 24, 2017 Those usually need a couple of components etc but simple enough. You will need a heatsink though 1 Quote Link to comment Share on other sites More sharing options...
Benno Posted September 24, 2017 Author Share Posted September 24, 2017 I was thinking I'd just use a LM7805 with a diode and a couple of capacitors, but something like that would probably be a better solution. Although so far my spend has been about $10 bucks for the arduino nano, some resistors, zener diode, relay module and an IP56 enclosure to suit. A $5 regulator to protect my $2.50 arduino nano and $1 relay seems a but overkill haha. Once I get it working properly I'll chuck up a schematic, a parts list and my code. 2 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted September 25, 2017 Share Posted September 25, 2017 Out of curiosity- What is the purpose of the diode in your LM7805 circuit? the LM7805 is fine (and cheap) i just went with the larger one because in the specs somewhere it used the word "beast" in relation to its 5A output capacity....I'm a sucker. The Lm7805 has overtemp and over current protection so really is a bloody good deal. 1 Quote Link to comment Share on other sites More sharing options...
Benno Posted September 25, 2017 Author Share Posted September 25, 2017 Diode probably not really necessary, there to protect against any back EMF from the automotive circuits. Battery should basically act as a massive sink and absorb any spikes from large motors such as the starter but I already have a few 1N4007 diodes lying around which should do the trick. I'm generally not stressing about protection etc, if the rev limiter fucks out then I won't be any worse off then I am currently. I'm not planning on revving to hit limiter every time I drive it or anything. 1 Quote Link to comment Share on other sites More sharing options...
flyingbrick Posted September 26, 2017 Share Posted September 26, 2017 off topic BUT I had some TINY 12v relays turn up yesterday. something like 7mm x 8mm x6mm.. so awesome. Quote Link to comment Share on other sites More sharing options...
NickJ Posted September 27, 2017 Share Posted September 27, 2017 5 hours ago, flyingbrick said: off topic BUT I had some TINY 12v relays turn up yesterday. something like 7mm x 8mm x6mm.. so awesome. Transistors? 1 Quote Link to comment Share on other sites More sharing options...
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