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 Post subject: Inductance to Digital Converter
PostPosted: Tue Sep 17, 2013 10:27 am 
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Limitless Design Possibilities

Applications for inductive sensing range from simple push buttons, knobs, and on/off switches to high-resolution heart rate monitors, turbine flow meters, and high speed motor/gear controllers.
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Texas Instruments designers have developed an entirely new data converter with the LDC1000 inductance-to-digital converter (LDC) designed specifically for inductive sensing applications.

The LDC uniquely combines all of the external circuitry on chip that is normally required to simultaneously measure the impedance and resonant frequency of an LC resonator. It then regulates the oscillation amplitude in a closed loop to a constant level, while it monitors the dissipated energy of the resonator. This leads the accurate measurement of inductance of the front-end LC circuit, which enables precise measurement of linear/angular position, displacement, motion, compression, vibration, metal composition and new applications which will be conceived by designers. All of this can be done in the presence of oil, dust, dirt and moisture unlike most other solutions.
EDN.com review.

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Last edited by abecedarian on Wed Sep 18, 2013 11:36 pm, edited 2 times in total.
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 Post subject: Re: Inductance to Digital Converter
PostPosted: Tue Sep 17, 2013 3:04 pm 
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interesting.


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 Post subject: Re: Inductance to Digital Converter
PostPosted: Tue Sep 17, 2013 11:15 pm 
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That's what I thought too.

The implications and applications for things automotive, aerospace and industrial this device claims to provide are immense. Theoretically, the fuel injectors' solenoid coils could be used to detect the piston position within the engine. Crankshaft, throttle, wheel position could be determined with substantially more significant accuracy than anything any current hall effect, optical or variable reluctance sensor can.

The more I think about this, the more I think about what can be done with it... and I'm nearly dumbfounded by it... and totally amazed no one else thought of it.

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 Post subject: Re: Inductance to Digital Converter
PostPosted: Wed Sep 18, 2013 8:38 am 
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well......

VR sensors are really really good at telling you when the tooth crosses centerline and once you have that you have crank or wheel position to crazy good precision, if you can process the signal. Current stuff is good here

What I'd be interested in the new chip for is injector dead time. I would love to have feedback to tell me when the injector valve moves off the seat and when it gets back home to the seat.


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 Post subject: Re: Inductance to Digital Converter
PostPosted: Thu Sep 19, 2013 12:44 am 
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True, VR sensors work well, but require things such as the duration between pulses and external signals to indicate a known position to calculate the dynamic position. This device could use a progressively tapered metal target around the flywheel or a crankshaft pulley and know the exact crankshaft position at any time without the overhead of calculating timing durations and external triggers and skipped teeth. It also could detect the teeth on the flywheel and only require a single 'pulse' to correlate that to a known crankshaft position.

I also want to take back my comment in my previous post about using the injector to sense piston position. This wouldn't work unless it was direct injection and some other details were worked out. But a coil embedded in the area around the



You mentioned measuring injector dead time and that I can see as a valid use.

The evaluation module for this has a detachable 'detector' coil included on the board, and this has a void in the center. You could center the injector nozzle over this hole, or maybe enlarge the hole so the nozzle can be within it so fuel sprays through and the coil should be able to pick up when the pintle becomes unseated and reseats. You might even want a variable pressure regulator so you can check dead times against fuel pressure too.

The MCU on the EVM board- MSP430F5528, can run up to 25MHz, has RTC, 128KB flash and 8KB SRAM + 2KB SRAM is USB mass storage device mode is not being used, and has a sample rate well over 100000 samples per second for a single channel. So, set up the RTC on the chip, and either configure one GPIO for interrupt, or use a second ADC channel, so it can detect when the injector is switched on and off. Log the time when the injector is fired, when the pintle is off the seat, when the injector is released, and when the pintle is back on the seat.

I don't know what effect the injector's coil and it's field would have on the unit but the changes in pintle state should show up as some change in the field. Makes me wonder if it wouldn't be possible to superimpose or multiplex the unit with the injector coil, maybe by treating the ECU signal to fire the injector as an AC signal and creating a virtual ground midway between the injectors 0v and 12v? I think, I'll leave that up to the EE's in the community.

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My O5E candidate: 1982 Honda CX500TC motorcycle.


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 Post subject: Re: Inductance to Digital Converter
PostPosted: Sun Sep 29, 2013 10:40 pm 
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Win up to $3000 with a valid design using the LDC1000.
http://www.edn.com/contest/ti-challenge ... est-bti-en

*Contestants must be members of EDN living in the United States (excluding Puerto Rico) or Canada (excluding Quebec).

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My O5E candidate: 1982 Honda CX500TC motorcycle.


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