Tach voltage not +12v

[rusefillc]

with D1 removed voltage is 9.9v

with R46 value lowered to 470 tach voltage 11.5v

[andreika-git]

https://github.com/rusefi/alphax-4chan/commit/4de32993da84c7dde138b381038f24e7c7060564

[ElDominio]

RevE still not ok

In 12v mode, still spitting out around 4v

[rusefillc]

@Qwerty-OFF says

Первый шаг отпаять D1 или D9 (светодиод TACH)

Второй посмотреть осциллографом что происходит на левой ноге R47

[rusefillc]

Baseline test in NJ

1K load actual result: tach LED does not blink 0v<>1v square wave with "5v" tach mode 0v<>2v square wave with "12v" tach mode

[rusefillc]

removed D9 nothing has changed - same 0/1 or 1/2v levels

left side of R47 constant 12v

[rusefillc]

1K load was a BAD TEST

without any load, with D9 removed I have happy 0v/+12v on tach output!

now going to return D9 since did not test without load :(

[rusefillc]

@ElDominio it seems to work fine on bench

@Qwerty-OFF says it could be about your specific resistance on specific tach.

@ElDominio can you please try with tach disconnected - would it be 9v or 12v without tach? @ElDominio can you measure tach resistance to GND?

[ElDominio]

Hi, in the local tests I have done:

1) With nothing connected, it behaves as expected 2) With an older 12V tach, voltage drops as seen on the scope, tach does not move 3) Works fine with logic based tachs (5v), since they seem to only use the square wave to drive a motor 4) In 12V cases, we usually use the 5v output to drive a N2222 transistor pulled up to 12v, which then is used to drive the tacho. This works fine

[rusefillc]

@ElDominio are you looking for any changes on rev G like making the N2222 official right on the board? not sure if things would stay configurable

@ElDominio the safest option would be to provision for maybe even through hole N2222 right on 4chan but have it not populated by default, would you like that?

[ElDominio]

Having space for a 2222 THT, sounds at least like a decent fix to make it somehwat configurable, and I'd like it in all boards, I had totally forgotten about this

How would we switch between soldered-on 2222 and logic level?

In fact, defaulting to 12v and removing something is my preferred fix

[Qwerty-OFF]

Now we have a transistor like N2222 pulled up to 5V. It can also be pulled up to 12V by additional control signal from MCU. What needs to be added?

[ElDominio]

So when I have issues with 12v tach, I usually use the Tach output on the ECU to drive a 2222 pulled up to 12V on the output, and then this produces a clean 12v square wave

[ElDominio]

Pullup is 1k

[Qwerty-OFF]

Configurable pullup: Low-side MOSFET:

[rusefillc]

Reopening to gather more notes

[ElDominio]

RevG can change voltages just fine