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For any add-on boards such as VR conditioners, optos and OEM interface boards
By zylinx
#44623
romP44 wrote:
Fri Aug 07, 2020 10:12 am
If you have max coil primary voltage at 400V :
- 1N4004 forward voltage: 1.1V
- Zener voltage: 100V
- Opto forward voltage: 1.3V
=> 400-1.1-100-1.3 = 297.6V

I = U/R = 297.6/1100 = 0.271A => 271mA

Max current for 4n35 is 1A for t <10 μs. So it should be fine.
But I have no idea about peak voltage duration...
Continuous max forward current of 4n35 is 50mA.
Thanks romP44, so because of the HV Zener we get such a reduced duty cycle and can run 271mA, makes sense.
PSIG wrote: I have diagnostic LEDs on my board designs, and they are surprisingly useful at higher speeds or tooth-counts. While you can't see individual flashes except at cranking and perhaps idle (even a 60-2 wheel is a blur at cranking), the eye can notice skipped or long pulses and other anomalies. Note the diag LEDs on boards such as the MiniMAX-A2 and DSC are on the output side, so indications are not of input signal activity, but conditioner output results (what Speeduino should see).
Good to know! My input LED will suffice for me, but maybe if I make few more boards I will add output indicator.
I wonder how hard It would be to make an Indicator LED blink on every 2nd / 3rd /4th pulse. divide the coil pulses.

I would like to report my setup has been working great,
no false triggering with the 100V Zener that I can see. :mrgreen:

I copy pasted some 'moving average window' code just to get it up and running,
still going to rewrite the code to try get it a little more responsive.
even though its close to perfect.
when I'm done I'll pastebin the code if anyone is interested.

Here are some janky vids.
First video my multiplier was not correct, displaying 1/2 my RPM.

https://youtu.be/DKDiTAEt7bc
https://youtu.be/4OLsk4QgkhE
By romP44
#44631
Frequency can be divided using a Flip-Flop https://www.electronics-tutorials.ws/co ... unt_1.html.
We can divide frequency by 2, 4, 8...
Would need some jumpers to select the division ratio (applied only the LED, output to the Speeduino must not be changed).
What are the required ratio?

I would like to add a diagnostic LED on the PCB I'm designing. Unfortunately, the Schmitt-trigger inverter gate SN74AHC1G14DBVR can supply only 8mA (High and low level output current).
Continuous output current is 25mA, so I don't know what is the real limit...
https://datasheet.lcsc.com/szlcsc/18091 ... _C7469.pdf
User avatar
By PSIG
#44679
As another source, spark frequency is also divided in the TachOut signal from Speeduino… ;)

romP44 wrote:
Sun Aug 09, 2020 9:13 am
… I would like to add a diagnostic LED on the PCB I'm designing. Unfortunately, the Schmitt-trigger inverter gate SN74AHC1G14DBVR can supply only 8mA (High and low level output current).
Ah, the challenges. Beyond the possible current limitations; keep in-mind if you want to power an output LED with the signal, an added resistor and LED can act like either (or both) a voltage divider, and a voltage regulator circuit (similar to a Zener regulator). Either way, it can lower the shared output signal voltage. You may need to choose another LED power option.
By romP44
#44693
You are right. I'll add a transistor.
This is the first time I calculate resistors required for a transistor. Feel free to check it.
schematic.PNG
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By romP44
#44741
romP44 wrote:
Sun Aug 09, 2020 9:13 am
Frequency can be divided using a Flip-Flop https://www.electronics-tutorials.ws/co ... unt_1.html.
We can divide frequency by 2, 4, 8...
Would need some jumpers to select the division ratio (applied only the LED, output to the Speeduino must not be changed).
What are the required ratio?
In the end, I will not implement a frequency divider because space on PCB is limited and additional cost.
By romP44
#44909
New version without transistor: I replaced 74AHC1G14 (max current output 8mA) by 74LVC1G14 (max current output 32mA)
schematic.PNG
schematic.PNG (37.15 KiB) Viewed 609 times
By NickZ
#45297
that original circuit was really only made to protect the input from any thing above 5v, some fords use a 12V pull up on their hall sensors. wasn't really made to take much more than that and wasn't made for triggering off a coil.
By romP44
#45328
Done, to be tested! :)
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By romP44
#45357
And it works!
The LED is blinking at idle, I did not check at higher speed.
Luminosity is low as duty cycle is low, but still visible.
I had to enable trigger filter (weak was enough), else, speed was doubled.
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