From: Bill Putney on 11 Mar 2010 13:12
> Toyota throttle has 2 hall effect sensors...
Well Jim B. says that they cost 10 times what a pot. would cost, so *no*
manufacturer would *ever* use them - so your statement just *can't* be
true. [rolls eyes] I guess that Toyota didn't check the price on the
parts before they designed them in - yeah - that must be what happened.
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')
From: Bob Cooper on 11 Mar 2010 14:21
In article <OtydnXBOAPs28AXWnZ2dnUVZ_rudnZ2d(a)speakeasy.net>,
> > Though recollections get hazy, I recall the vacuum wipers always
> > slowing down - maybe even stopping, when the throttle was opened.
> > And I remember heater doors clunking closed too.
> > Think these were cars in the 1960's, Chevy, Olds, Pontiac is what I
> > drove then.
> > --Vic
> since when did pieces of s from the 50's and 60's, with little if any
> gas flow dynamics engineering, represent modern vehicles???
Pay attention. They were talking about throttle effect on vacuum
Did you confuse that with EPS and hydraulics?
From: Bob Cooper on 11 Mar 2010 14:22
In article <rsmgp5t82blf3lo6kpgno8o267227cdhtg(a)4ax.com>,
> EVERYONE is using drive by wire, or has plans to. It has MANY
> advantages - and is no more prone, by design, to failure than a cable.
Sure. That's why all those cables in past cars went haywire and opened
up throttles. Preaching to the choir, you are.
You recall all the incidents of million-car recalls because of that,
> A very simple electrical fault can totally screw up a mechanical cable
> connection too. A bad ground can allow fault current to flow through
> the throttle cable, melting the plastic sheath, causing a sticking
> throttle. It has happened. I've seen it.
Sure. Thousands of time, probably. Millions of cars were recalled for
that, weren't they? Throttles going wide open all over the place.
Those were terrible times.
> Mechanical devices are MORE subject to failure than electronics
Right. That's why multiple transitors, resistors, lines of code, servo
motors, and yards and yards of wiring are so much more dependable than a
cable and a return spring attached to the driver's foot via a pedal.
Just makes sense.
From: clare on 11 Mar 2010 15:49
On Wed, 10 Mar 2010 20:10:37 -0800, jim beam <me(a)privacy.net> wrote:
>On 03/10/2010 06:32 PM, dizzy wrote:
>> David Skelton wrote:
>>> I thought the main reason for ABS is to maintain steering control when the
>>> brakes were pressed too hard, so hazards could be avoided.
>>> But, ABS does not
>>> work so well in the very wet or icy conditions.
>> Sure it does.
>not always dude. stopping distances with abs can be considerably
>longer, especially in conditions like snow.
>> It can't perform miracles, however.
Like I always say - it just makes sure you hit what you hit SQUARE.
From: clare on 11 Mar 2010 16:04
On Wed, 10 Mar 2010 20:28:26 -0800, jim beam <me(a)privacy.net> wrote:
>On 03/09/2010 10:15 PM, Rodan wrote:
>> clare(a)snyder.on.ca wrote:
>> Toyota throttle has 2 hall effect sensors. The output of one tracks the
>> other but is offset. In other words, one starts at say, 0 volts, and the
>> other at, say 1 volt - and they increase in step with each other.
>how can that be true???
>hall effect sensors are used for gross position detection, not small
>scale linear deflections. they can be used for "wot" detection, but
>their ability to work over a wide positioning range is limited. that's
>why they're used in timing for things like crank position [rotational]
>sensors where you're counting pulse rates, not graduation functions.
You are wrong. Hall effect sensors are used instead of potentiometers
in all kinds of "variable output" controls including the throttles on
virtually all the electric scooters and e-bikes you see out there.
They are called "Ratiometric Linear Hall Effect Sensors.
The present invention incorporates a system for varying the output
signal and regulating the power consumed by an electrical device. It
achieves its purpose by moving a magnet relative to a Hall effect
sensor which is responsive to an intersecting magnetic field. The Hall
effect sensor creates an electrical output signal which determines the
input signal of an output element of the device. The electrical Hall
effect sensor signal thereby controls the output signal emitted by the
electrical output element. The magnet is moved using a movable
element. Since the location and movement of the magnet regulates the
Hall effect sensor output signal, the output signal of the electrical
device as well as its rate of change are regulated using the movable
element. In order to conserve power the Hall effect sensor element is
usually not energized when the device is in the "off" mode. However a
switching means correlated with the position of the movable element
energizes the Hall effect sensor when the magnet has created a
magnetic field of acceptable density and direction.
SS490 Series Standard Miniature Ratiometric Linear Hall-Effect Sensor;
radial lead IC package
Actual product appearance may vary.
l Small size
l Low power consumption
l Single current sinking or current
sourcing linear output
l Built-in thin-film resistors - laser trimmed for precise sensitivity
and temperature compensation
l Rail-to-rail operation provides more useable signal for higher
l Responds to either positive or negative gauss
l Quad Hall sensing element for stable output)
l Current sensing
l Motor control
l Position sensing
l Magnetic code reading
l Rotary encoder
l Ferrous metal detector
l Vibration sensing
l Liquid level sensing
l Weight sensing
SS490 Series MRL (Miniature Ratiometric Linear) sensors have a
ratiometric output voltage, set by the supply voltage. It varies in
proportion to the strength of the magnetic field.
A new Hall effect integrated circuit chip provides increased
temperature stability and sensitivity. Laser trimmed thin film
resistors on the chip provide high accuracy and temperature
compensation to reduce null and gain shift over temperature.
The quad Hall sensing element minimizes the effects of mechanical or
thermal stress on the output. The positive temperature coefficient of
the sensitivity helps compensate for the negative temperature
coefficients of low cost magnets,
providing a robust design over a wide temperature range.
NOTE: Products ordered in bulk packaging (plastic bags) may not have
perfectly straight leads as a result of normal handling and shipping
operations. Please order tape packaging option for applications with
critical lead straightness requirements.
Also see: http://www.allegromicro.com/en/Products/Part_Numbers/1321/
A1321, A1322, and A1323
Ratiometric Linear Hall Effect Sensor ICs for High-Temperature
Output voltage proportional to magnetic flux density
Ratiometric rail-to-rail output
The A132X family of linear Hall-effect sensor ICs are optimized,
sensitive, and temperature-stable. These ratiometric Hall-effect
sensor ICs provide a voltage output that is proportional to the
applied magnetic field. The A132X family has a quiescent output
voltage that is 50% of the supply voltage and output sensitivity
options of 2.5 mV/G, 3.125 mV/G, and 5 mV/G. The features of this
family of devices are ideal for use in the harsh environments found in
automotive and industrial linear and rotary position sensing systems.
Each device has a BiCMOS monolithic circuit which integrates a Hall
element, improved temperature-compensating circuitry to reduce the
intrinsic sensitivity drift of the Hall element, a small-signal
high-gain amplifier, and a rail-to-rail low-impedance output sta
>> That way
>> the CPU can tell if one has failed, and if the two outputs are shorted
>> together (one bypassed) If either accelerator sensor fails, the CEL comes on
>> and the vehicle is limited to 1/4 throttle. If both fail, the throttle
>> gets set to a fast idle position and the rpm is controlled to normal idle
>> speed by programmed [missfire] (injector cut) The throttle position sensor
>> (throttle feedback) also has 2 hall effect sensors 0 and they have
>> [different] "rates" - the primary gives a higher signal linear from closed
>> to open, while the secondary reads full by about half throttle.
>> If the CPU senses a single TPS failure the engine is reduced to a fast idle.
>> iF BOTH tps fail, it is returned to base idle - and if the ECU determines
>> that the throttle has NOT closed - the engine is shut off. The ECU has 2
>> CPUs. the main monitors all sensors and [controlls] the entire power-train -
>> engine, transmission, cruise control, traction control, etc. The "sub"
>> monitors all sensors and all outputs - and monitors the main CPU via a
>> "watchdog" program. The sub ALSO controls the electronic throttle. Both
>> cpus control an output transistor that feeds power to the throttle control
>> motor - BOTH must be turned on in order to open the throttle. They are
>> series connected). If either CPU senses a problem and shuts down, there is
>> no throttle. Gets pretty darn difficult to envision any electronic error
>> that could cause uncontrolled [accelleration], particularly without
>> registering a code and turning on the CEL.
>you can have a hall effect sensor at the end of the rotational travel
>for wot, and you can compare that output with the potentiometer output,
>but the graduated positional sensing is typically done with a potentiometer.
Nope. You are WAY out of date. Hall effect sensors measure magnetic
>> Once upon a time there was a cable from the gas pedal to the
>> throttle that operated the throttle butterfly. The throttle
>> shaft had a position sensor that told the computer how much
>> power the driver was demanding.
>> Someone figured they could save money by eliminating the
>> cable and attaching a position sensor to the gas pedal to tell
>> the computer the driver's gas pedal position. The throttle
>> shaft still had to have a position sensor to let the computer
>> know its state compared to the pedal position, so the cost
>> tradeoff was one less cable and one more position sensor.
>> But there were more costs. The throttle butterfly no longer
>> had the driver's foot power to move it, so they had to add a
>> servo device to the throttle to provide power to the butterfly,
>> and controlling power transistors to drive the servo, plus
>> a reprogrammed computer to keep track of it.
>> More complexity, added electromechanical hardware, higher
>> cost, multiple new interfaces, and more computer operations.
>> The whole thing sounds like a joke invented by Rube Goldberg.