group "tweecer" @YAHOO.COM (PART 2)
The op amp circuits are dependent mainly on the ratio of the various
resistors in the circuit, not really the op amp itself.
Check out this site:
http://ourworld.compuserve.com/homepages/Bill_Bowden/opamp.htm
The only real decision is how to power the thing so you can get both the
positive and negative swing of the sensor. If you power the op amp from the
car's 12V you will only be able to amplify the 0 to whatever output from the
sensor. If you use a plus and minus 5 volt power supply, you can amplify
both swings and have a maximum of 5 volt output since the op amp can never
make more than it's power supply voltage.
Matt
Matt Robinson
Engineer
Lockard & White, Inc.
<http://www.lockardandwhite.com/>
www.lockardandwhite.com
"Not everything that can be counted counts, and not everything that counts
can be counted."
- Albert Einstein
_____
From:
tweecer@yahoogroups.com [mailto:tweecer@yahoogroups.com] On Behalf Of
Matthew Minor
Sent: Tuesday, February 21, 2006 11:19 PM
To:
tweecer@yahoogroups.com
Subject: RE: [TwEECer] Re: Datalogging an Add on Knock Sensor
That's what Paul suggested as well. It sounds like you have an electronics
background, so I was just curious how easy it is to pop in an OP Amp and
know exactly what the gain is. If I want say a 100X gain, how easy it is to
have repeatability between OP Amps and the various components needed to make
a 100X gain OP Amp assembly ? Or would I have to calibrate each assembly ?
Thanks for the help.
Matthew
Matt Robinson <mrobinson@lockardandwhite.com> wrote:
You could use a op amp circuit to amplify the AC from the sensor then
rectify it after you amplify it.
Matt Robinson
Engineer
Lockard & White, Inc.
<http://www.lockardandwhite.com/>
www.lockardandwhite.com
"Not everything that can be counted counts, and not everything that counts
can be counted."
- Albert Einstein
_____
From:
tweecer@yahoogroups.com [mailto:tweecer@yahoogroups.com] On Behalf Of
Matthew Minor
Sent: Tuesday, February 21, 2006 5:03 PM
To:
tweecer@yahoogroups.com
Subject: Re: [TwEECer] Re: Datalogging an Add on Knock Sensor
That .7V drop is the concern. The knock sensors used on some of the EEC-IV
Fords were about a 0-1V discharge so once detonation starts, the diodes are
filtering that out. Granted a larger voltage is possible from these sensors
but the problem is the engine is an oversized exploded hand grenade much
after 1V. I need something closer to a 0-5V output. That way, mild and the
usual engine noises won't make it through the rectifier but the diode
doesn't drop so much out that it misses the initial detonation. Perhaps the
newer knock sensors on the EEC-V's are capable of giving a wider output. If
so, I'd sure like to see a link to their performance.
Matthew
fusco531 <fusco531@hotmail.com> wrote:
I wouldnt worry too much about the Voltage drop across tthe diodes I
think its somewhere around .7v. Converting AC to DC is actually quite
simple with a full wave bridge rectifier circuit, but you end up with
pulsating DC so your datalog may end up all over the place, you can
smooth the pulse by using a small capacitor if needed. I would try
without first. As for low voltage protection, you will need to
determain the output AC range of the sensor and add a voltage
divider into the circuit to limit the input into the computer.
I just ran a quick simulation using 120 VAC converted to approx 4.5
VDC, so it is possible.
Hope that helps
John
--- In
tweecer@yahoogroups.com, Matthew Minor <matthewx@...> wrote:
>
> Thanks for the replies. I fully intend to figure a way to do
this. One of the problems with converting AC to DC is that a certain
amount of voltage is required to push through the diodes. The good
side of this is that low, inconsequential signals won't be
datalogged. The flip side is that if the knock sensor doesn't
generate a high enough voltage, detonation may be occuring before the
diode allows the current to flow through making it impossible to
datalog it during detonation. I am sure that if a knock sensor with
the proper output can be found, minimal signals can be filtered out
and the beginning stages of detonation can be detected so that
optimal timing can be arrived at safely. I will keep everyone posted
and encourage everyone to keep the info flowing.
>
> Matthew
>
> Daniel Nicoson <A6intruder@...> wrote:
> We've discussed this every now and then. I think the one thing us
> home-tunners are missing is a good way to determine optimum spark
advance.
> That's why I was hoping someone really smart would surface with a
useful ion
> sensing ignition circuit.
>
> The EEC IV can log through that pin you mentioned anything that
varies
> between 0 & 5 volts. So you would need to build an interface
circuit to
> turn the raw AC output into a useable 0-5 volts.
>
> I didn't know Vovlo had a separate system. Research that, maybe
you could
> add that and log it's output.
>
> I know the mid 1990's Mk-7 had knock sensing on the 5.0. Have we
hacked
> that computer? I don't think the earlier generation was all that
good
> running on the edge for power purposes. I think they were good
keeping
> Grandpa from trashing his Mk-7 as he thundered up the mountain with
the boat
> on behind.
>
> We have a local dyno shop with two 2005 Mustangs. They LOVE the new
> generation of knock sensor that is on those machines. They feel
they
> couldn't run near as much boost without the new knock sensing.
>
> Dan Nicoson
>
> -----Original Message-----
> From:
tweecer@yahoogroups.com [mailto:tweecer@yahoogroups.com]On
Behalf Of
> mdl3333333@...
> Sent: Tuesday, February 21, 2006 4:50 AM
> To:
tweecer@yahoogroups.com
> Subject: Re: [TwEECer] Datalogging an Add on Knock Sensor
>
>
> I think this could be done not sure if it would prove very useful
or not.
>
> I don't think you will want to just wire knock sensor to the
computer they
> are not 0-1 volt, more like 0-1000 volt. Now you not like ever see
1000
> volts
> out one, not even likely you go over a 100 volts, but still wiring
knock
> sensor to a computer input not rated for a knock sensor, could kill
the
> computer. And the output is A/C you likely need to turn it in too
DC and
> give some
> means being sure the volts can go over a safe limit. Maybe could
build
> some
> thing fairly ez.
>
> Knock sensor is bit like a mic, as you buzz it output volts, the
louder the
> more volts, but it tune for Hz witch match the ping for the
engine, has to
> do
> with bore size mostly, so if a noise falls in to the tuned Hz it
make lot
> more volts for given loudness.
>
> I think the early ford computer trip around 3 volts or more as a
ping.
>
> I think newer setup do more filtering of the output to try to get
better
> read off the knock senor.
>
> I never hard of "Wideband knock sensor" I think this mix up of
terms.
>
> Volvo do use a close loop spark setup, but I think it uses Knock
sensor a
> lot like everyone else's. It works as I under stand it, by
starting with a
> base timing, what ever is in the tune and then adding timing tail
engine is
> right at edge of pinging. I hard they have computer just for
controlling
> this.
> I do not know if all there cars use this and I don't thing they
only ones
> that use some thing like this. These engines have good bit of
compression.
>
> more common way is the other way around, to set a good base spark
timing,
> then use the knock sensor to pull timing if some thing didn't go
right.
> Also
> with less compression there are less gains for trying to cut the
timing
> right
> to the edge, but with newer engines sporting more compression a
lot more
> engines are getting knock sensors.
>
> I think you can date log a knock sensor like you would a wide band
O2, you
> maybe even get away with just wiring it up, but I think I would use
some
> thing
> to make sure it couldn't spike the computer, and I think you need
make the
> AC in to DC volts. But will what you data log be readable helpful,
hard to
> say. I hard number of people say that a lot of high HP engines
are too
> noisily
> for most knock sensors to work well.
>
> Well if you try it lets us know how it works out.
>
> Mike.
>
>
>
> In a message dated 2/20/2006 10:01:56 P.M. Central Standard Time,
> matthewx@... writes:
>
> Has anybody tried/done this on an EEC-IV computer ? I figured if I
> could run a Wideband O2 and be assured that my mixture was right
> throughout all of my engine operation ranges, that perhaps a knock
> sensor could then be datalogged in place of my Wideband O2 to be
sure
> my timing was as close to optimal as possible. One problem I
noticed
> with most of the early EEC-IV knock sensors is that they generated
an
> AC voltage which probably cannot be datalogged, and that they only
> generated a 0-1V signal as opposed to a Wideband 0-5V. Also, very
few
> of the EEC-IV processors work with a knock sensor so that pretty
much
> prevents datalogging them through anything except the pin 27
connection
> ordinarily used for the Wideband O2's. I have heard Volvo knock
> sensors are Wideband though I am not sure about the signal being
VDC.
> I know this isn't necessarily high on most people's ideas to
implement,
> but it does seem like an extra tool for safely learning how to run
the
> most timing AFTER being sure the A/F is correct. Any feedback on
how
> to do this is appreciated. Thanks for the help.
>
> Matthew
