elesjuan

iTrader: (11)

I'm sure at this point in time I have a pretty priceless look on my face...



At one point in time I removed all 3 of those transistors for a different mod, but ended up putting them back in for this. The center one (Q10) is what shipped with megasquirt when I ordered my kit, Q9/Q11 are MPS2222A transistors that I had to pickup from Radio Shack. I Think when I put them back in I didn't check the manual or wiring diagram, just looked like they should go that way, so its how I installed them. Megamanual.com isn't opening up right now so I can't go look at the assembly guide, but looking at my hard copy of wiring diagram Pin 1 should be ground (base), pin two is the base, and pin three is the collector..

Right now I'm beside myself. First I feel pretty stupid for not RTFM on those, secondly I can't believe the car actually runs with them installed in reverse.

Don't have time to mess with them today because I have to pack my **** for another work trip this evening but I'll be sure to reverse those back and put some 470 ohm resistors in place of the 1k ohm. Keeping my fingers crossed.

Braineack

iTrader: (62)

whoops.. that'll do it. I thought they looked out of place, but chalked it up to the v2.2 board as I'm not intimate with it. I believe the flat side should face the outside of the board.

elesjuan

iTrader: (11)

Well now.. That was a fair tradeoff.

Desoldered the transistors, switched them around, soldered them back on. Removed my 1kohm pullups for some 470 ohms. Cleaned up everything, hooked up stim and got a +5v square wave from both A and B channels. Looks good. Hooked it up in the car just how I have been testing, +12 coming from battery to coils, good strong charge on the battery.

Cranks, cranks, cranks cranks cranks.


N O T H I N G A G A I N ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

Stock coils no work.

*sigh*

elesjuan

iTrader: (11)

Took some voltage measurements and I'm starting to see why it won't fire the coils.

A: 0.128 volts
B: 5.0 Volts
C: 5.0 Volts
D: 5.0 Volts
E: 0.128 volts


Don't pay attention to the resistors in the photos, those are old pictures I'm using to draw on. Too lazy to get out my slr, take photo, process, edit, just to post this...


Swapped around the Q9&Q11 so they're installed properly. Swapped out the 1k Ohm resistors on the bottom for the pullup with some 470 ohm resistors.


Anyone have a guess why I get +5 volts into the Pullup, but only 0.128 volts out? Pulled a brand new resistor out of the package and hooked it up to my power supply. +5 volt to lead 1, ground to - input on DVM, them + input from DMV to Lead 2 of resistor. Get 5.09 volts with or without resistor. I know that resistors aren't supposed to limit voltage, only current.


Is it possible that maybe my resistors are bad, or the Q9 & Q11 went bad from being reversed? Also noticed when I was pulling Q9 off it had a solder bridge between two of the pins...

Making some progress, I think. I'm confident when I can get +5 volts to the pullup and output that my COPs will finally fire properly. Input from ALL welcome, please and thank you!

patsmx5

iTrader: (16)

I can damn near guarantee you burned up those 2n2222's when you unsoldered them. My experience is two seconds of hot solder kills them. I'd get put two new radio shack 800 ma NPN's in there and give that a go.

ALSO: This could be very important. Radio Shack sells those as a box of 2n2222's but when you open them they're actually like 3 different current ratings. So make sure you're using the big ones to be safe.

elesjuan

iTrader: (11)

Those are MPS2222As from JapShack, the high current versions they sell. I'm not sure if they're burnt out or not from the desolder / solder.. I used a 2800$ desoldering machine to remove them so I'd hope that didn't kill em. They're like a dollar for a two pack anymore so I'll pickup some more.

This still doesn't explain where the missing voltage is... Or does it?

elesjuan

iTrader: (11)

Went back over to the shop today and removed Q9 & Q11, replacing them with some 2N2222A transistors, like Megasquirt BOM calls for. Come to find out the frequency between the 2N2222A and the MPS2222A are different, and Bart thinks that might cause something strange to happen.

Used a Tektronix TDS400 Scope to verify my spark outputs and snapped some quick shots with my phone for ***** and giggles.


Spark output A

Spark output B

Spark output A

Spark output B



Don't mind that solid line that runs along the bottom, I forgot to turn off channel 2 input. Only have one good input probe for this scope, so I couldn't show both at the same time.



Now, lets see what happens. Reassembling megasquirt right now and going to try the stock coils first.

elesjuan

iTrader: (11)

Nope! Nothing.

Cranks, fires injectors, will NOT spark coils!

Brand new 2222s installed, 470 ohm resistors. I'm about to turn the 2222s around and put 1kohm with a short on one of the 2222s and see if it'll start. This is seriously retarded.


Won't spark the stock coils or any cops in any config. I have ******* verified the output of the megasquirt and posted photographic proof, tested for frequency with my shitty DVM @ the coil packs with a 4hz frequency on cranking! Why won't they spark!?!?

elesjuan

iTrader: (11)

Tried to reflash the firmware, reloaded my msq, nothing.

Shows frequency while cranking, won't fire the coils. This here will prove they'll fire if I do it manually:



Wish the mic on my phone was better. It sounds like a shotgun, firing off the fuel thats been pumping into the motor unburnt because these stupid floppy pieces of **** won't fire with megasquirt. This should prove they're ******* wired correctly and operational so its something wrong with my piece of **** megasquirt. What, I don't even know where to start. Complete and total failure.

patsmx5

iTrader: (16)

Your spark outputs should be spitting out a ground for that brief moment, right? Not a positve. IE, one side of the coil is always +12V. The other side is hooked up to an igniter, which is just a transistor. It sits there open separating the collector (other side of ignition coil) and the emitter (ground).

Doesn't it need to see something less then the collector (+12V) to open and connect collector to the emitter?

I think your output is like backwards. It needs to be a +12V pull-up with the dips being shorts to ground that will trigger the igniter.

Or am I way off?

elesjuan

iTrader: (11)

Its been my understanding these types of coils (including stock coils) need +5 volts to trigger, and trigger on the falling edge.. IIRC...

The spark mod was what I found on DIY's website and all the DIY miatas on here use.

I have a pair of VB921s, maybe I should figure out a way to use those.

patsmx5

iTrader: (16)

I'll have find my brain later and do some research to verify or deny what I said earlier. PM Joe Perez and respectively beg him to comment. He knows more about all this than I do.

Joe Perez

iTrader: (8)

Sorry for the delay.

The spark outputs of the MS are typically set to produce a positive pulse of +5 volts to trigger the ignition system, where the length of the pulse is equal to the dwell period. The actual circuit commonly used to achieve this is a bit odd (the CPU turns a transistor on to pull the output down and then turn the transistor off to allow the output to go high) however it has proven reliable and effective.

In both the stock Miata ignition system (all years) as well as all known instances of a Toyota COP module, a positive trigger voltage causes the coil primary to conduct, and the falling edge of the trigger causes the primary coil to stop conducting, leading to a spark event.

With regard to Q9 and Q11: The MPS2222A and the ZTX450 have the same pin orientation. In post # 14, 18, 21 and 24, they are all installed backwards. The silkscreened notch in the part outline deontes the emitter position. In the plastic-bodied TO92 parts, the emitter is the left-most pin as you are looking at the printed side of the component with the pins pointing down. It is possible that they were damaged by this.

I would not worry about the replacement parts you picked up. 2N2222A is just fine. We're not operating anywhere near the speed rating on these guys.

I'm somewhat curious about the scope shots you posted in #27. Were those taken with the MS hooked up the coils, or just sitting on the bench? I ask because I'm not accustomed to seeing such clean rising edges on these trigger lines when under load. (BTW, you do know that the TDS420 has a floppy drive that you can save traces to in PC-readable form, right?)


So, where do you stand now? Are you back to running on the stock coils, or is it all still blotto?


Here's my thinking on your original problem. The fact that you could run one coil or the other, but not both, suggests that perhaps you weren't supplying enough current to them. Yes, the trigger lines on those things do suck up a bit of power. The available current is a function of the resistor laid between +5v and the upper terminal of the LED. DIY uses 100 ohms in the MSPNP, and I think I've got 330s in mine. 1k is just way too much in this position.

Do you have an inductive current probe for the 420? If not, can you do another scope capture of the trigger line while cranking, first with only one coil connected, and then with two? I'd like to see 1ms/div and 1v/div.

Obviously it will be necessary for the thing to be working to achieve this. If you're still getting nothing, put ye olde' scope on the CPU outputs which drive these guys- pins 7 and 8. You should be seeing a normally high signal which goes to ground for firing. (the circuit is inverting.) If you are getting that, then the rest is just basic point-to-point troubleshooting.

elesjuan

iTrader: (11)

Thanks Joe, I hoped you'd chime in eventually.

With how these coils fire on the falling edge, does that mean spark triggers should have +5 volts on them at all times with key on / engine off? Cause mine don't.

Yeah I installed those transistors in reverse when I first installed this unit on my car, and somehow drove the car for quite some time under this condition. Attempting to fix it caused some, well, issues. No spark. I have since fixed this problem with 2n2222a transistors properly installed and 470 ohm pullups. Still nada.

Honestly you easily know 200 times more about that scope than I do as my knowledge of it is pretty limited to measuring frequency on something simple, like this. If you notice the flat line between the square wave, that was channel 2 which I couldn't remember how to turn off until later. Would've used that second channel input but we didn't have a good working probe that'd produce a clean signal. That was tested on the bench with stim, not on the car which explains the strong rise / fall. Unfortunately testing on my car with a scope won't be easily possible for a while as that piece of test equipment belongs to a former boss of mine.

With 2n2222A transistors installed, 470ohm pullup, won't spark even a single coil. Stock or not.

Well with Q9/Q11 installed in reverse with a solder bridge on one of the resistors, it ran perfectly fine with stock coils but would only fire one COP at a time hooked up as stated.

With Q9/Q11 installed in reverse with a solder bridge... Do you think it could've started to burn out the CPU?

If I can ever get this damn thing running I'll inquire about the inductive pickup probe for that Scope, its a very nice unit just wish I knew how to use it and it was mine. lol.

elesjuan

iTrader: (11)

Just took that. The 2n2222a installed properly.

Update:

Just tested "Key on / Engine Off" Voltage at pin 7 and 8 on Megasquirt. Got +5 volts. Checked for frequency there with stim for wheel, have same frequency (just with my shitty DVM..) on both 7 and 8. Tested Cont between 7 and R25, 8 and R28. Both 0 ohms.. so there is good connection between processor and R25/R28.

Joe Perez

iTrader: (8)

No. The trigger signal should normally be at 0v. To understand how it all works, you have to keep the dwell time in mind. Let's assume you have dwell set to 2.5ms. Every time a reference tooth comes around on the CAS, the MS starts a countdown timer. It knows what angle the reference tooth occurs at relative to the crank, and it knows how fast the engine is turning, so it can calculate how many milliseconds it will take from the time the reference tooth passes by until the crank reaches TDC. From the spark table, it also knows how many degrees before TDC it wants the spark to happen, and from this it calculates the number of milliseconds that will pass before the spark needs to fire.

I'm going to pull some completely arbitrary numbers out of the air as an example. I'm too lazy to do the actual math here, so don't think these are actual data.

Suppose that the engine is turning at X RPM. From the time the reference pulse occurs until TDC is 10ms. The ECU wants to fire at 10° BTDC, and it calculates that will occur in 7ms. You have a 2.5ms dwell, so at 4.5ms after the reference pulse, the ECU turns the SparkA output channel on (+5). This causes current to start flowing through the ignition coil. Then, 2.5ms later, it turns the channel off, and the coil fire.

So the output needs to be low most of the time. If it were high, then the coil would conduct continuously, and the igniter would overheat and burn out. In fact, the reason you need to disconnect the igniter when reflashing is that the spark outputs float high during this time, because the CPU is offline and it can't pull the outputs down.


Truthfully, I can't offer you a lot of specific guidance at this point in getting the thing to work again. It's possible (though improbable) that the CPU was damaged. My advice would be to get the thing on the bench, on a stim, and use the scope to take some measurements.

Start by measuring pins 7 and 8 at the CPU. These should normally be at +5, and go to ground momentarily. Basically the inverse of what yo have in post 27. If you don't see this, remove the transistors in D17 and D19, and measure again.

You can also measure at pin 3 of the transistors- this is the collector, which is the terminal furthest from the silkscreened notch. At this point, you should get the signals in post 27, normally ground, with momentary pulses to +5.

If you pass the first test but fail the second, then you either have bad transistors, faulty pullup resistors, broken traces, or bad solder work. Check across R25 and R28, as these are between the CPU and the transistor base. Check for continuity from the emitters to ground (you should have it) and then between the bases and collectors to ground (you should not).

I'm afraid that this is just going to be a matter of some tedious point-to-point troubleshooting. Have the schematics handy, and take notes.

Back at harris, we had a Tek TCP202 probe. It was nice because you could take very accurate current measurements on DC circuits, which is impossible with a normal passive inductive probe. On the downside, it cost about $1,800. We had to really beg to get it.

The point was that I was going to have you measure the current on the trigger wires, though now that I think about it, a voltage measurement will do just as well. It'll have to be with the scope, as I want to see whether the trigger line is able to source enough voltage to drive the coils, which we'll see in the rising edge and MaxV of the trigger waveform.

elesjuan

iTrader: (11)

Anybody know a Miata could run on one cylinder??



Back to the lab for more bench testing. Didn't get **** out of it, pulled it apart and replaced the pullup with a 100 ohm. Hooked it up and took these measurements:

Just for you, Joe!













Came home, Installed it on the car and got nothing. Finally managed to tweek it into running, and the video posted above is the result. All four coils sounded and felt like they were triggering, but one was loud and three were quiet. Really frustrated One by one I hooked up the OLD corolla coil packs I've had for a while and it started running better.

Now, I finally have the god damn car running, and with COPs none the hell LESS! Thank you, good god I'm glad its over.

Pat: Sorry man, those RX300 coils are bad. They sound like they're triggering but they're not putting out any spark. I was gonna give em to you if this ended up working. All the same, Joe, Pat, Scott, Everyone.. Thank you.



That should have sound on the video but I don't think it does.. My laptop has been acting strange lately. I don't think it likes to transfer sound to the docking station if I don't actually reboot windows. Ohwell.

Joe Perez

iTrader: (8)

The sound came through loud and clear!

Congrats on getting it working. That last set of scope traces looks about right- you can see how the inrush current is pretty large, and the voltage gradually climbs but never makes it anywhere near 5 volts. Those suckers are an amazingly heavy load on the trigger line. That's the reason for the smaller value resistor on the pullups.

I finally found an image I'd been digging for. This is what it looks like driving the stock 1.6 igniter and coils with an EMU. Upper trace is trigger voltage, lower trace is coil primary current. Pretty much the same as you got, with an even lower peak trigger voltage.