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Science with your Sound Card!
Sound Card - Engine Crank and Cam Sensor Simulator
The above image shows the Daqarta Generator running the Engine_Sim Engine Crank and Cam Sensor Simulator Mini-App that is included with Daqarta. (Note that this remains fully functional after the Daqarta trial period... it's completely free.)
The mini-app simulates the output from an engine's crank or CKP (green) and cam or CMP (purple) position sensors, for testing an Electronic Control Unit (ECU) or Module (ECM) without an engine present. It has a DESIGN Mode with separate CRANK Design and CAM Design selections that allow you to specify all relevant parameters for your engine.
(You can also simulate 3-sensor systems that replace the single CMP cam sensor with separate TDC and CYL sensors. You'll need a sound card with multi-channel outputs for that. The inexpensive (under US $20) 5.1 Channel CM6206 USB device discussed in Sound Card Performance Tests is a good choice for this purpose.)
The default design has 36 Crank teeth with one missing, and one Cam tooth that is high for 10 degrees of cam revolution, from 160 to 170 cam degrees. That aligns it over Crank teeth 33 and 34 on the first of the two crank revolutions.
As shown, the DESIGN Mode button has been toggled to SIMULATION Mode, with most of the design options disabled. (You can choose from saved designs; you don't have to go through the design process each time you simulate.)
During simulation, the default mode is Constant RPM, whose speed defaults to 1000 RPM but can be easily changed with the Set Constant RPM control. (That control is hidden in the above image... see below.)
Toggling the Constant RPM simulation mode advances to 600-6000 RPM Sine Cycle, and Set Constant RPM becomes RPM Test Cycle with a default of 10 sec. This mode smoothly cycles the simulated engine speed back and forth between 600 and 6000 RPM (or whatever limits you specify), at a rate set by the RPM Test Cycle control. The above image was captured with the output waveform about one-third of the way through that range; the instantaneous speed is shown via the RPM mode readout on the Frequency Counter at the bottom of the image, as 2031.526 RPM.
The Sine Cycle can be toggled to Arbitrary Schedule Cycle to run your own RPM test schedule. A default schedule is included that ramps from 600 RPM to 3000, holds, ramps to 6000, holds, and returns to 600 RPM over the RPM Test Cycle interval.
You can easily create your own RPM schedule using the included Arb_From_List mini-app. You just give it a list of times and RPMs and it does the rest, including displaying RPM versus time so you can verify that it's what you intended. The schedule used for the default is:
;sec RPM 0.00 600 2.00 3000 4.00 3000 5.00 6000 6.00 6000 8.00 600 10.00 600
The simulation uses a trick to allow the trace to synchronize to the crank reference: The first pulse after the gap is made slightly taller than the rest, and the Trigger Level (horizontal blue line near the top of the trace) is set to catch this pulse but miss the rest.
Without this trick, each trace update would sync to whatever pulse from the stream happened to arrive next, and the reference gap would roll arbitrarily across the trace. (The ECU wouldn't care, but it would be hard on the eyes. The Frequency Counter could still read the correct RPM, by setting the Cylinders control to twice the number of actual teeth present on the gear, not counting any missing teeth.)
See the External Connections subtopic under Engine Crank and Cam Sensor Simulator Mini-App for a discussion of how to connect your sound card outputs to an actual ECM/ECU.
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