For discussion of Speeduino compatible boards designed / built by other members of the forum and for guidance around making such a board
By hytrozion
#60953
Hello guys,

I'm making my own board to make it PnP...


the ignition coil (wasted spark : 1-4 & 2-3) on my car appear to be controlled by signal (gnd ?) pulse
here is a similar ignition coil
Image
(simplified scheme on my car) Image
55 and 37 are the two pin from the ECU, 3 is 12V

inside the original ECU, there is a mosfet for each connection (connected to the drain pin), and the source pin is connected to the gnd of the ECU via a big resistor

so I cant use the chip TC4424A for my board.
My question is could I use the same injector driver, the chip VNLD5090 to pulse signal to the ignition coil ?

thanks.
User avatar
By PSIG
#60959
hytrozion wrote: Tue Jan 31, 2023 7:03 pminside the original ECU, there is a mosfet for each connection (connected to the drain pin), and the source pin is connected to the gnd of the ECU via a big resistor
so I cant use the chip TC4424A for my board.
Yes, you can, and should. The TC4424 is a signal amplifier, used to increase signal authority to the actual power device (IGBT, BJT, etc) that drives the coil with high-amps. The controller pin output is too weak to firmly switch the driver, so the TC4424 (or similar), along with a capacitor for power, is used to quickly switch the driver hard high and hard low. You need a driver suitable for an ignition coil, that the TC4424 will switch.
hytrozion wrote: Tue Jan 31, 2023 7:03 pmMy question is could I use the same injector driver, the chip VNLD5090 to pulse signal to the ignition coil ?
No. The spec's on this device are too low, especially in voltage (C-E breakdown) to directly drive an ignition coil. Ignition coils typically produce up to 450V of flyback EMF on firing, and the driver must be able to withstand this repeated inductor abuse. IGBTs are popular for this purpose, but there are other types that have been used. Here is a random but robust and popular ignition IGBT datasheet for example: ISL9V5045
#60961
No. The spec's on this device are too low, especially in voltage (C-E breakdown) to directly drive an ignition coil. Ignition coils typically produce up to 450V of flyback EMF on firing, and the driver must be able to withstand this repeated inductor abuse.
could I just put diodes after the signal output to prevent flyback ?

or could something like this work ?
Image
User avatar
By PSIG
#60964
That's not what I'm saying. The coil pack you have pictured does not have internal drivers. Your old ECM had those (marked 99029). Speeduino does not have drivers, but does have TC4424 signal output, to connect to a driver device. You are missing the drivers the old ECM had.

High flyback voltage to the µC of a coil firing is not the first issue, but the flyback that will kill a VNLD5090 or other lower-voltage device that powers the coil. They are not meant to drive the coil(-) amps and survive high-voltage flyback. You need coil drivers, such as IGBTs, as described in my earlier post.

The image below from the Wiki shows the Speeduino IGNx signal from the TC4424, and the coil, and you are missing the coil driver between them. Does that make sense?

Image
#60970
PSIG wrote:The image below from the Wiki shows the Speeduino IGNx signal from the TC4424, and the coil, and you are missing the coil driver between them. Does that make sense?
oh that make sense now, so something like that should do the trick right ?
Image
LPG2CV wrote:You could use a bosch 211 externally as the driver. Or use smart coils.
I would like to keep the maximum of original component from the engine, this is not a viable option for me.
User avatar
By PSIG
#60973
hytrozion wrote: Wed Feb 01, 2023 10:03 am oh that make sense now, so something like that should do the trick right ?
That's the idea. I did not review it carefully, but noticed the VDD to the TC4424 should not exceed 10V, as the gate voltage (VGEM) of that IGBT is 10V max. Typically, 5V is used.
LPG2CV wrote: Wed Feb 01, 2023 4:59 am You could use a bosch 211 externally as the driver.
@hytrozion - he said this, as the Bosch 211 coil driver module (for one example of many options) can connect between the IGN outputs (TC4424) of Speeduino, and your coils. This is a common and easy way to integrate coil drivers without the cost and time of a new board design, and to remove noisy HV circuits from the ECM case. If the drivers must be in the ECM to use an unmodified wiring harness, then your diagram above is an optional direction. Your boards will need full functional field testing to confirm noise is not an issue.

Not meant in a bad way, but you seem to know just enough to be dangerous. :lol: We learn by doing. Keep doing.
#61011
PSIG wrote:That's the idea. I did not review it carefully, but noticed the VDD to the TC4424 should not exceed 10V, as the gate voltage (VGEM) of that IGBT is 10V max. Typically, 5V is used.
I made changes thanks.
PSIG wrote:@hytrozion - he said this, as the Bosch 211 coil driver module (for one example of many options) can connect between the IGN outputs (TC4424) of Speeduino, and your coils. This is a common and easy way to integrate coil drivers without the cost and time of a new board design, and to remove noisy HV circuits from the ECM case. If the drivers must be in the ECM to use an unmodified wiring harness, then your diagram above is an optional direction. Your boards will need full functional field testing to confirm noise is not an issue.
80€ is expensive, I will stick with my board and hope there will not be a lot of noise :P
JHolland wrote:Collector to coil, emitter to 0V
thanks :D
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