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EFIE with opamp
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tangomar Offline
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Post: #1
EFIE with opamp
I am reading the EFIE Manual from Eagle-Research. I just wonder if there is a specif reason why they use an astable configuration with transformers and so on instead of a simpler opamp adder.

I understand that when off the EFIE should behave as it wasn't there but that can be done with the switch.

Am I missing something?

Thanks,
Omar
05-22-2008 01:32 PM
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mike Offline
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RE: EFIE with opamp
Nope. You're not missing anything. Go ahead and try building one with an op-amp. I have a sideline project going using op amps. The 555 timer versions are sensitive to temperature, and I'd like to resolve that. If I had more time, that design might already be developed.

And yes, you can cut the efie out of circuit with a switch. No problem.

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05-22-2008 01:45 PM
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tangomar Offline
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RE: EFIE with opamp
How about something like this?

It would require probably something like a rail-to-rail low-noise opamp and 1% resistor. R7 is the pot (500 linear).

I spice simulate this with LTC and it looks good with the ideal opamp, if I have time I'll try with something more realistic.

Omar


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05-22-2008 05:25 PM
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mike Offline
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RE: EFIE with opamp
Plug it into a breadboard and see if it works. Let me know how it goes.

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05-22-2008 10:47 PM
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tangomar Offline
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Post: #5
RE: EFIE with opamp
I am playing with the idea to use a microcontroller with AD/DA intergrated (like MICROCHIP PIC16F684-I/P). This would solve some people's issues about the lower/upper range saturation.

My idea is to apply a voltage offset (maybe different programs) only when the oxigen sensor voltage is inside a "safe" range (let's say 0.3-0.8V). This should avoid the ECU panic mode.

I've never done anything on cars so I have tons of questions...

For example, is the battery voltage stable or it can get really messy when the alternator charges it? Probably a dedicated power supply for the IC might be recommended in case.

Thanks,
Omar
05-27-2008 05:35 PM
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mike Offline
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RE: EFIE with opamp
Just stick a good 9 volt fixed voltage regulator in there. I put a 4.7 uF cap between power and ground as well. That should clean it up for you. But yes, the voltage is pretty dirty and you need to hide your circuit behind some protection.

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05-28-2008 12:28 AM
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