No Tach Signal
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Read the manual to see if your question is answered there before posting. Many users will not reply if the answer is already available in the manual.
If your question is about troubleshooting, configuration, or tuning, you MUST include your processor type (MS-I or MS-II) and code version in your post. If your question is about PCB assembly or modifications, you must also include the main board version number (1.01, 2.2 or 3.0).
If you have questions about MS1/Extra or MS2/Extra code configuration or tuning, please post them at www.msextra.com Such questions posted here will be moved to: a temporary MSextra sub-forum, where they will be removed after 7 days
The full forum rules are here: Forum Rules, be sure to read them all regularly.
No Tach Signal
I am assembling a megaquirt II Version 3.0 Board code version v2.920.abs.s19. I hooked my board to a Stim and I am able to see the feedback for the TPS, Coolant Temp, Intake Air Temp, and if I make an adjustment and cycle power I see a EGO change also. I am not getting anything on my tach. I have XG1 and XG2, Tachselect and Optoin, and Tsel and Optoout Jumpered. I also have a zener installed and jumped out at D2. I can see a square wave pulse on my Oscope around 5.1 volts which seems to respond correctly with the 2 pot adjusters. If I remember correctly I had the span set to roughly 2ms to see the pulse. I can see the pulse on both sides of D1 and the jumpered D2. I also see it on one side of R12. On the other side of R12 the voltage drops to roughly 1.26 volts (as I expect), but the square wave doesn’t look nearly as nice and my Oscope no longer recognizes it as a duty cycle, but there is still a rough signal that reacts to me adjusting the pots. I see this voltage (1.26V) at pin one of the opto-isolator( which from the data sheet 1.3V is typical). (I also see ground at pin 2 and pin 6. What type of voltages should I expect on the opto-isolator pins and how can I test if it is actually firing. Thanks Mark
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: No Tach Signal
This is a test I wrote for testing with just a volt meter:
With the Megasquirt powered up, apply 12 volts to pin 24 or TachSelect, and check the voltage on the TSEL jumper with a voltmeter. You should read zero volts. Next, ground pin 24 so it has no volts on the input circuit, and check TSEL's voltage again. You should see 5 volts there. Let me know what you find.
It could also be adapted to an oscilloscope with the same rules: 0 volts on the output when the input is energized, 5 volts when the input is grounded.
With the Megasquirt powered up, apply 12 volts to pin 24 or TachSelect, and check the voltage on the TSEL jumper with a voltmeter. You should read zero volts. Next, ground pin 24 so it has no volts on the input circuit, and check TSEL's voltage again. You should see 5 volts there. Let me know what you find.
It could also be adapted to an oscilloscope with the same rules: 0 volts on the output when the input is energized, 5 volts when the input is grounded.
Re: No Tach Signal
I appreciate your help. I haven't had internet access for several days. I traced the problem to my stim timing circuit. I actually did some more searching and came across a reply you gave for testing the op-amp and found mine to check out ok. I then hooked it up to my truck and got a tach signal. All is good. again Thank you.
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Matt Cramer
- Super Squirter
- Posts: 2951
- Joined: Sat Jul 03, 2004 11:35 am
Re: No Tach Signal
You're welcome.