Logic spark wiring

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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

I have a jb perf 4 channel board and a vr conditioner board in place already, so top slot space is becoming scarce.

The first gate driver proto board I made put the 4427s directly over the ms2 cpu :shock: I suspected gremlins may fall out of the conductors going to the 4427s and fall into the ecu so I pulled it out before running it.

I have some ideas, currently I have pn2907 PNP's in the 4 channel board with a 5v "buss bar" feeding the emitters. ala current pull up circuit.

The pull down resisters are a last ditch patch hold out if all else doesn't work out until a Jean gets around to laying out a new 4 channel board.

I have some MIC4420 6 amp t022 package gate drivers coming that I hope to message into the four channel board in the igbt positions.

I would suggest at the very least updating the diagram in the manual to include a pull down resistor, until the all encompassing driver circuit is finalized and boards become available and the circuit is obsoleted.

The 4k7 value is what is suggested for the pull up resistors for the npn drive circuit listed above the 5v pnp drive circuit, but looking at it again, the voltage divider thing isn't a issue in that circuit. Initially i was think something 100k to 1 Meg pull down without doing any calculations.
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Re: Logic spark wiring

Post by racingmini_mtl »

I've had a look and can pretty much take the current 4-channel driver board and add 2 TC4427 and 4 resistors (and a 5V pad) and get the hybrid board that can be used with either IGBTs or the TC4427s. The only potential issue is that it uses an SMD package for the TC4427 but it's an SOIC-8 which is probably one of the easiest SMD package to solder by hand. The resistors are through hole.

Jean
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

nice,
the SOIC 8 won't be any harder to solder than the Q5-Q7 transistors.
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

The MIC4420s came in today and I got them placed. still need to get the supply bypass capacitors placed. hope to test em sometime this week
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Re: Logic spark wiring

Post by racingmini_mtl »

prof315 wrote:
prof315 wrote:
prof315 wrote:Just about ready, I should be testing this weekend.
We have had a couple of small setbacks with the car we will be using as a test mule but hope to have things resolved and a report on how things work in a few days.
Success! Toyota COPs, Honda COPs, LS coils and 01 and later VAG coils all work with a 10 Ohm resistor on the output.
It's good to see this confirmed especially since you've covered most of the popular ones that had been problematic (even though I've used this circuit in my rugged ECU and it was tested with a couple of different setups, as mentioned before).

However, it would be interesting to have more details on your setup, i.e., which components you used and how they were connected. Did you use the simplest schematic posted before and where did you connect 5V and ground? I'm not sure there is a need to worry about the power supply and grounding scheme with such a small effective current so if you can give those few details about your tests that may confirm my thinking.

Jean
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prof315
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Re: Logic spark wiring

Post by prof315 »

I used the original, basic schematic with 2 TC4427s and 2 8 pin DIP sockets sourcing 5V and Ground from the proto area, 10 ohm resistors on the outputs, and actually took the triggers directly from JP2 on an MS3 daughterboard. We used an old floppy drive 34 pin ribbon cable to run the wires to the proto area.
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Re: Logic spark wiring

Post by racingmini_mtl »

I'm wondering if that's the best place to ground the circuit or if it would not be better to ground it at the coil. Remember the TC4427 works in push-pull so it might feed back some noise from the coil to the MS board ground. That would be from the input side of the coil so that would likely not be significant especially if the input capacitance is low. I may be overthinking this.

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dontz125
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Re: Logic spark wiring

Post by dontz125 »

If there's any issues, perhaps the TC4427s can be grounded at the outlet end of R43.
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Re: Logic spark wiring

Post by racingmini_mtl »

Good point. So grounding at the MS board would be the way to go and if it is found that there is indeed some noise issues in some cases, using the R43 location would be the one to use. Otherwise, the proto area would be the most convenient place for most setups.

Jean
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

what is the rational of the 10 ohm resistor on the output? The IC has limiting under short circuit condiction.

I was under the impression the most important job of the control signal coming out of the gate driver going to the logic controlled coil is getting the coil side transistor to turn off as quickly as possible to set up the greatest field collapse into the secondary coil and fire the plug.

If this is correct ground for going high trigger coils (ala vag) and the supply bypass caps for the going low trigger coils need to be considered.
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Re: Logic spark wiring

Post by dontz125 »

Sorry, missed this question. I can't answer to the caps, but the extra limiting resistors are there to protect the MS 5v power supply. The internal resistance of the TC4427 is 7-10 Ohms, or 500-710mA from a 5v supply. This is beyond the normal capacity of the voltage regulator, and enough to trigger the polyfuse. By adding low-power resistors, not only do you avoid the regulator or polyfuse from shutting down the entire ECU, a sustained short will pop the affected limiting resistors and relieve the load.

The second TC4427 schematic, added as a suggestion if the low-resistance VAG coils had difficulty with the previous circuit, features a dedicated self-limiting 5v regulator that operates in parallel to the main board regulator. In this case, no limiting resistors are fitted.
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

Made a noob mistake, which should probably be noted in the documentation and schematic.
Any resistor between the CPU and gate driver should be removed!!!!
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Re: Logic spark wiring

Post by dontz125 »

? The input pins are high impedance; an additional series resistor shouldn't have any effect.
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

The max4427 gate drivers I was using have a note on page 4 of the datasheet that "The MAX4426/MAX4427/MAX4428 have easy-to-drive inputs. However, these inputs must never be allowed to stay between VIH and VIL for more than 50ns."
The mic 4420s datasheet only stated "The MIC4420/4429/429 accepts any logic input from 2.4V to VS without external speed-up capacitors or resistor networks"

However both exhibited random weirdness in the total circuit.
Being able to trigger the vag coils sometimes, and sometimes not.
Testing at the box output plug good all the time, and at the coil plug at the end of the harness good sometimes and sometimes not (test done by checking for line voltage and holding ground by alternating setting "going high and 'going low' in tuner studio with a multimeter and being able to drive a test led connected to the box plug in test mode, I didn't have access to a portable oscilloscope).
Rebuilding the harness and supply wiring circuit by circuit.
Then eventually having the gate drivers fail.
The coils and harnesses were tested many many times manually with a 4.5v battery source as the trigger during the last week.

Right now the circuit is working quite well with the 1k ohm series resistors removed and a couple ixys ixdi404 inverted gate drivers with ms set going low, I will report next week when the max4427s and tc4427s come in and I can drop em into the sockets

The analog devices MT-097 TUTORAL pdf "dealing with high-speed logic" was very informative.

Assuming a 1pF capacitance between the cpu and the gate driver which is a circuit greater than 2 inches total length (have to apply that transmission line stuff), the 1k Ohm resister I left in series would cause a 2200 nS ish rise time.

I read in the TC 4427 datasheet "MOSFET driver inputs A and B are high-impedance, TTL/CMOS compatible inputs. These inputs also have 300 mV of hysteresis between the high and low thresholds that prevents output glitching, even when the rise and fall time of the input signal is very slow. "

However, given the amount of variability in circuit layout and selecting available gate drivers instead of the recommended gate drivers that will happen with open source and novices stuffing the circuit into existing boxes, and given that "very slow" is a relative term and "high speed" usually deals with the well under 1000 nS rise and fall times (the 2200nS ish rise times with the 1k resistor in series may be more than "very slow"),making a note to remove any series resistor between the cpu and gate driver may prevent others from catching this gremlin too.

but I may be way off base, I'm not very good at this stuff.


new board layout, I like the idea of the "fuse" resistors, besides the chip sockets I have socketed 1/4 amp polyfuses on the output instead just in case one of the vag coils ignitor transistor takes a dump along with a socketed 1/4 amp polyfuse on the pos input before the bypass capacitors.
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Re: Logic spark wiring

Post by piledriver »

However, these inputs must never be allowed to stay between VIH and VIL for more than 50ns.
Sounds like you may want a schmitt trigger on the input.
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Re: Logic spark wiring

Post by jsmcortina »

piledriver wrote:
However, these inputs must never be allowed to stay between VIH and VIL for more than 50ns.
Sounds like you may want a schmitt trigger on the input.
Or just use the other part that is actually suitable?

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racingmini_mtl
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Re: Logic spark wiring

Post by racingmini_mtl »

jsmcortina wrote:
piledriver wrote:
However, these inputs must never be allowed to stay between VIH and VIL for more than 50ns.
Sounds like you may want a schmitt trigger on the input.
Or just use the other part that is actually suitable?

James
Especially since I don't think the right one is less available than the "wrong" one(s).

Jean
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

the tc4427s came in today and work well with the vag coils with ms set to going high, so the box is buttoned up and put back up under the dash
This little project is in parallel with another project i'm working on requiring gate drivers switching a pulse transformer driver transistor, I assumed the outputs from the cpu were digital and didn't consider something like a Schmitt trigger as necessary, but I will keep that in mind for the other project.
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weeblebiker
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Re: Logic spark wiring

Post by weeblebiker »

nm
wrong post
btw the tc4427 gate drivers are working dandy with vag cops set on going high
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Re: Logic spark wiring

Post by savagerocco »

What happened to the schematic diagrams on this thread? I got my parts and was ready to build a board and all the pics and diagrams are gone.
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