Slow_Old_Car Posted March 28, 2007 Share Posted March 28, 2007 Alright, so megasquirt is a huge hit, it's run by thousands of people on dozens of makes worldwide... Alot of us run it, and it works well, we love the adjustability, etc... What i'm wondering about now, is durability. The production side of the community has addressed this with MS-II v3.0 with it's upgraded circutry for being more rugged in the automotive world. But what can we as end users do? I'm no electrician, but i've been kicking around the idea of ways to buffer or clean the power that feeds the boxes, add in layers of protection beyond a simple inline fuse. Figured a few of the more electrically savvy people here have probally done somthing to this effect and i'm just not using the right verbage to describe what i'm thinking. Basically devices to handle power surges and/or help smooth the power flow to a MS box. Whats the name of the item i'm looking for here? I'm getting to a point that i want to be able to do stints in my car that could range hundreds of miles (SEZ9 for example). But i want to build in some protection that is more-so than just carrying a entire spare MSnS setup. In my case: MS2.2 v3.0, 029q2 file set on MT 2.25b, mapdaddy 4-bar, 440cc supras, resistor pack. Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 28, 2007 Share Posted March 28, 2007 A filter? Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 28, 2007 Share Posted March 28, 2007 I've been running a V2.2 board in a road racer for over three years now, and it's been very reliable. There really isn't much you need to do as far as additional filtering or surge protection. If you use a relay board, it is already protected with fuses. You can replace the fuses with circuit breakers that automatically reset. They make them that are a drop in replacement for the fuses on the relay board. If you are not using the relay board, just replace your fuses with auto circuit breakers. Quote Link to comment Share on other sites More sharing options...
Pop N Wood Posted March 28, 2007 Share Posted March 28, 2007 The ultimate protection would be some type of DC to DC inverter. That way your output would be a clean 12 volts no matter what the input voltage looked like. You would even be protected against EMP ( But probably massive overkill. Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted March 28, 2007 Share Posted March 28, 2007 I have used a car stereo filter on my Dodge Dart, which has an incredibly noisy electrical system. While the noise doesn't seem to do any physical damage, the filter cut down on resets very well. One more tip - route the signal wires leading to the Megasquirt away from high voltage ignition wires. Having these lines touch the ignition wires can cause resets or issues with the firmware, even if they are still insulated. Quote Link to comment Share on other sites More sharing options...
naviathan Posted March 28, 2007 Share Posted March 28, 2007 Hehe this is funny. I was just schooled on this not too long ago. What's "padding" the voltage in the MS-II is the LM2937 voltage regulator. Look it up on this forum, there's even a link to the datasheet. I would imagine though the MS-I has this as well. The only other things to add in are filter capacitors to clean up any noise in the signal. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted March 28, 2007 Share Posted March 28, 2007 Hehe this is funny. I was just schooled on this not too long ago. What's "padding" the voltage in the MS-II is the LM2937 voltage regulator. Look it up on this forum, there's even a link to the datasheet. I would imagine though the MS-I has this as well. The only other things to add in are filter capacitors to clean up any noise in the signal. I searched for LM2937, and this thread is all that came up. Do all Megasquirt versions have adequate spike protection for all the inputs (and in front of the LM2937)? I have a feeling that this is what Slow_Old _Car is thinking of. <> Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 28, 2007 Share Posted March 28, 2007 The MS does not need any additional filtering. A car stereo filter on the +12V input to the MS can't hurt. If your engine is running great, chances are you don't need any more filtering. A filter can consist of many different elements, but typically an RC (resistor-capacitor) network will do the trick. The ideal filter would only allow DC to pass through it (blocking all other frequencies). The equation to determine the low frequency cutoff for a low pass RC filter is as follows: Freq = 1/2*PI*R*C Things to consider: - R cannot be too high as too much voltage will be dropped across it, lowering the voltage that the MS sees. - C Must have a rating of at least 25V to handle any voltage spikes. You can use your algebra to solve for the different components. It is not this simple though, but for this purpose, it will work. In the radio filters there is most likely a ferrite bead (inductor) along with a capacitor to make up the filter. The ferrite bead has good filtering characteristics, with an extremely low DC resistance. Quote Link to comment Share on other sites More sharing options...
naviathan Posted March 28, 2007 Share Posted March 28, 2007 Actually it's z-ya that schooled me on it. Here's the thread: http://forums.hybridz.org/showthread.php?p=751117#post751117 Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted March 28, 2007 Share Posted March 28, 2007 Quote: Originally Posted by z-ya (in the other thread) "The Alternator voltage will never cause the MS to reset (unless it goes below 5.5V, or over 30V). In that case, nothing will work. As long as the +5V logic regulator is working OK, the CPU will continue to process instructions. If the regulator is not functioning properly, it will most likely destroy the CPU and other components running off the +5V logic supply (VCC). I've got 20+ years experience in electronic design and debug, trust me on this one." This is more on the order of what I was considering. Not a little hash in the DC, but a big voltage spike. (I've gotten between an alternator and the battery with a cable off, and got quite a shock). Worst case scenario would be as described above: smoke. I was wondering if some sort of zener controlled crowbar could easily be put on the supply line (set at 20 volts or so) to protect the LM 2937, and thus, presumably, the entire megasquirt device. I really don't have a nickel in this game (just carburetors here) merely curious. <> Quote Link to comment Share on other sites More sharing options...
eec564 Posted March 28, 2007 Share Posted March 28, 2007 The megasquirt actually runs off of 5 volts, not the 12-14 you have in the car. The LM2937 converts anywhere from 26 volts to 5.5 volts directly to 5 volts, with very high accuacy. A capacitor in the input circuit effectively takes care of any spikes and the regulated 5 volts out is very stable. Since the megasquirt outputs switch a ground signal, and the ground is common for the 5 volt and 12 volt circuits, so a drifting 12 volt signal dosen't really matter. The only wires that a decent amount of current flows through on the megasquirt are the ground wires, for turning on the injectors and firing the coil. There is very little reliance on the 12 volt supply for anything, and it is very well protected. Plus, your car dosen't run off of exactly 12 volts. The battery has a full charge voltage of anywhere from 11.5 to 12.5 volts, which drops to 10-ish when cranking, and 14.5-ish once the alternator kicks in. It makes a bigger difference with car stereos, because they draw far more power, and use the 12 volts directly to run an amplifier which you can hear the output of. If you're getting spikes for more than a few milliseconds up to 50+ volts, there is something majorly wrong with your car, and you'd blow up any OEM engine computer. Megasquirt would be more likely to survive, as you'd blow out a power regulator and maybe a capacitor or two, and be able to relace them with over the counter parts. Quote Link to comment Share on other sites More sharing options...
naviathan Posted March 28, 2007 Share Posted March 28, 2007 Megasquirt would be more likely to survive, as you'd blow out a power regulator and maybe a capacitor or two, and be able to relace them with over the counter parts. Ahhhh...my favorite part of MS...It's availability of parts and ease of repair. Especially when you're the one that put it together. Quote Link to comment Share on other sites More sharing options...
eec564 Posted March 28, 2007 Share Posted March 28, 2007 Ahhhh...my favorite part of MS...It's availability of parts and ease of repair. Especially when you're the one that put it together. Absolutely. That's something I also like about my Z. I can easily do all the work on it, and the various systems are seperate, so they're easy to troubleshoot and repair. Even the EFI system is independant of the rest of the car, and dosen't use fancy and obscure parts to run. Quote Link to comment Share on other sites More sharing options...
Matt Cramer Posted March 30, 2007 Share Posted March 30, 2007 I searched for LM2937, and this thread is all that came up. Do all Megasquirt versions have adequate spike protection for all the inputs (and in front of the LM2937)? I have a feeling that this is what Slow_Old _Car is thinking of. <> Yes. The V2.2 board has a Zener diode that protects it against many high voltage spikes, a capacitor for a little bit of noise filtering, and a diode to protect it from reverse polarity. The V3.0 board adds a metal oxide varistor for more protection. Quote Link to comment Share on other sites More sharing options...
A. G. Olphart Posted March 31, 2007 Share Posted March 31, 2007 Yes. The V2.2 board has a Zener diode that protects it against many high voltage spikes, a capacitor for a little bit of noise filtering, and a diode to protect it from reverse polarity. The V3.0 board adds a metal oxide varistor for more protection. Thanks, curiosity is satisfied. <> Quote Link to comment Share on other sites More sharing options...
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