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Any strange behaviour, crashing issues etc, post them here! Problems compiling the firmware should go in the General support section rather than here
User avatar
By turboedge
#47861
Gshorten wrote: this should not kill the TC4424, @ 12v through the 160 ohm
Hi, Sorry I did not see this sooner. I'll start with your answer which is your 4424 is dead. On the 0.4.4b/c the 4424's output actually goes though a 10 ohm resistor not a 160 ohm, but that is not the cause, though it is an issue. What type of coil are you trying to drive? More than likely it will operate at 5v, many people assumed that a lot of coils needed 12v because the earlier Speeduino boards limited the current to much for them to work at 5v, even though they should have. Switching to 12v, while not technically correct for the coil, allowed it to work with the higher resistance. The cause is that the 4424 is only rated for 18v, and you more than likely had a spike big enough to kill it. If you bought it from me send me a message on my website and I can arrange to get it repaired for you.

Weaver
By JHolland
#47868
Gshorten wrote:
Wed Jan 27, 2021 7:52 pm
the TC4424 is rated for 3amps out.
3A peak current - which is only for around a few micro-seconds maximum. The continuous rating is a function of the power dissipation and the thermal characteristics of the package and is around 44mA per channel (88mA maximum one channel). So a short can kill the TC4424 very quickly.
As mentioned above they are also vulnerable to spikes, in a load dump situation you can get 43V on the '12V' rail.
By Gshorten
#47927
Thanks for all the help. The new board tests good (still too cold to install), but I'm wondering if the coil I am using - the wasted spark bosch coil (Bosch 0986221048) as used in the ~2000 VW Jetta draws too much current for the 4424?. Is there a better alternative to that coil, or is there something I could add which would protect the 4424? BTW I was driving the coil with 5v.

I did try to replace the 4424 but damaged the circuit board in the process, I think it's toast :-( I did buy the board from you but I don't think it can be fixed now.
Also, just double checking - spark output triggers should be set to going low? This is, I believe opposite to what a megasquirt should be set to when using this coil.
User avatar
By PSIG
#47946
Just adding a few things that may be helpful :? :
Gshorten wrote:
Sun Jan 31, 2021 4:22 am
...I'm wondering if the coil I am using - the wasted spark bosch coil (Bosch 0986221048) as used in the ~2000 VW Jetta draws too much current for the 4424?. Is there a better alternative to that coil, or is there something I could add which would protect the 4424? BTW I was driving the coil with 5v.
Test! The original Bosch "smart" coil pack versions have contained different coil driver modules. Aftermarket versions ($25USD and up online) have often replaced the original driver modules in the packs with modern IGBT versions, requiring near-zero current. Yours could be either, and I can't be sure what I've got until I test them. I just connect 5V with a 100-ohm resistor and measure the current. It will either be effectively zero current (IGBT driver), or milliamps (original-type modified BJT driver).

The issue with the original-style "106B" coil pack modules is 5V requirement, but high current. 5V works, but needs the small-resistor higher-current, or a switched direct current source, as outlined in the Bosch datasheets. With the higher current, over-dwelling can toast any igniter driver, such as the TC4424. Control your dwell, and no problem. Not a big deal, but I prefer other passive ("dumb") packs and use an IGBT coil driver module anywhere in-line that's convenient. Yes, an additional part not packaged inside the module, but works with low-current and reliability. That's me. The 106B-type is fine; just know your parameters and exactly what you have.
Gshorten wrote:
Sun Jan 31, 2021 4:22 am
Also, just double checking - spark output triggers should be set to going low? This is, I believe opposite to what a megasquirt should be set to when using this coil.
Yes, they dwell with high signal (5V) and fire when going low. MS is a good source for concepts and technical data, but Speeduino is different in setup. I would avoid using MS references, as we have seen (and I have been) confused and frustrated when mixing the two. Use Speeduino setup instructions. Several systems use TS, but Speeduino is not MS.
By Gshorten
#47947
Fantastic information, thanks very much. I will test. So, If it's a high current version... limit dwell to say, 2.0 - 2.5 ms? Or, maybe get a newer aftermarket version...or as you suggest go with a dumb pack and seperate driver.
Update: just tested my coil, with 86ohm resistor at 5v I get 12mv.
User avatar
By PSIG
#47950
Correct and corrected dwell, just not over-dwell. We can get deeper into options, but I try to avoid complications, and you may not want that as you have enough on your plate right now. ;)

However, if you do, then you can bench-test for your minimum triggering current by simply swapping test resistors until you find one that triggers reliably at 5V, or whatever your exact regulated driver voltage is. I have found original 106B coil pack drivers that I have tested seem to work well at about 82-ohms. You could simply try that value at 0.5W, and if it's happy, then you don't have to worry about dwell so much. Don't forget the average power is used in dissipation calculations, and so the (roughly) 66% duty cycle (e.g., 2ms dwell, 1ms discharge at-speed) averages power lower.

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