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Old 01-31-2014, 09:53 AM   #1
JohnnieB
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Smile How the ITS works is now known.

I looked up the Patent number stamped on the ITS sensor and found out how it works.

In a nutshell: It is a proximity sensor and the current flow through it is proportional to the position of the plunger in the coil.

The controller provides power to it and measures the current flow. Different controller brands and models use different voltage source circuits and different current measuring circuits, so the throttle voltages measured are different depending on brand and model of the controller, but they all work the same since they all use the same sensor.

I haven't done any testing yet, but it looks like you can bench test the sensor by feeding it something in the 9V to 16V range (The voltage range will have to be refined) through a resistor (1K ?) and monitoring the voltage drop across that resistor while inserting a iron slug (Screwdriver or similar iron/steel rod ?) into the coil. If the voltage drop across the resistor changes, the sensor may be good, if it doesn't change, the sensor is bad.

Attached is a block diagram of the sensor and a copy of the patent documents.

----------
Wonder what other things can be discovered through patent numbers.
Attached Images
File Type: jpg ITS sensor - Block diagram.JPG (49.6 KB, 0 views)
Attached Files
File Type: pdf ITS Patent - 5247253.pdf (459.6 KB, 0 views)
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Old 01-31-2014, 10:32 AM   #2
simple man
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Default Re: How the ITS works is now known.

That is something I would never have thought to do, looking up the patent number of a device! Great info, John! Now I believe we are closer to the go/no go test!
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Old 01-31-2014, 10:41 AM   #3
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Default Re: How the ITS works is now known.

And that kids is what makes time travel possible ...... lol - Mayor
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Old 01-31-2014, 10:50 AM   #4
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Default Re: How the ITS works is now known.

Quote:
Originally Posted by simple man View Post
That is something I would never have thought to do, looking up the patent number of a device!...............
That is the Age and Treachery part of my signature block.
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Old 01-31-2014, 11:29 AM   #5
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Default Re: How the ITS works is now known.

JohnnieB you do good work. If you bench test one it would be interesting to measure the current drawn by the ITS. I will check the ITS current draw on my old golf cart this weekend.
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Old 01-31-2014, 04:37 PM   #6
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Default Re: How the ITS works is now known.

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Originally Posted by radioman View Post
JohnnieB you do good work. If you bench test one it would be interesting to measure the current drawn by the ITS. I will check the ITS current draw on my old golf cart this weekend.
I measured the current draw of the ITS in my old golf cart to be 1.5 milliamps when the solenoid clicks and it increases up to 2 milliamps as the pedal is depressed as the cart begins to move. I double checked my reading on the Simpson 260 to be sure. That diagram of the ITS explains the resistance reading I was getting with the different meters and why resistance readings cannot be used alone to determine if an ITS is bad.
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Old 01-31-2014, 05:31 PM   #7
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Default Re: How the ITS works is now known.

One thing to understand is that a well written pattent, gives enough information to protect the intelelectual property but not enough to make coppying easy or operation understood.

Many patents have intentilnally vague, flawed or misleading information.


What I expect is this.

The driver circuit has an occilator ( pictured), this will put a AC signal thru the inductor...that is variable due to the slug. beeing inserted and removed by various amounts.

The exact mechanism for resolving this AC signal and this variable inductance could be one of several.

It may be that the variable inductance, represents a simple AC resistance(inductive reactance) to the signal.

It may be that the variable inductance, represents an inductive component in the main occilator circuit, varing the inductance varies the frequency of the occilator..that is somehow resolved by the driver circuit.

One mechanism that i think may be possible, and can be seen in quite a few devices from the late 70's to early 80's ( remember golf cart tecnology is not generlly cutting edge), is the compared phase shift twin occilator circult.

Before we had hall effect devices, digital shaft encoders, infrared LEDs and the like inductive sensors where seen as a realy good option and more reliable than lots of other stuff.

This was not uncommom >

There where two occilators, one fixed and one variable, The fixed occilator may have inded been fixed or varied ( tuned) to suit the rest state of the variable one.

The inductive component caused the variable occilator to shift in frequency.

Because an actual shift in frequency was hard to detect with the technology of the time, a phase comparitor was used.

the fixed occilator and the variable occilator where fed into a differential amp......signals basicaly inverted and combined.
At rest because both occilators where on the same frequncy and 180deg out of phase there was no output of the dif amp.

as the variable occilator shifted frequency (and not by much) the phase of the two signals would shift compared to each other and an output would come from the comparitor.....this wave form looked like a sort of diagonal eye....as the difference was greater this wave form got bigger and wider.....it was refeered to as "opening the eye" opening because that is what it looked like on a CRO.

In some circuits this output was the rectified and may be filtered to produce a DC output that varied with the change of inductance.

this very same principle could be seen in inductive motor controlls, road way inductive loop detectors, modems ( back when they where as big as a bread box and weighed 20 pounds) and a range of other stuff.


The early circuits of this type, the fixed occilator had to be tuned manually to the rest state of the variable occilator....later circuits had a self tuning fixed occilator.

Unless you have access to the actuall circuit, to measure or observe waveforms.....this discription is not much hlep.

However, back when I was a young bloke and we did serial to paralall data conversions mechanically (tell that to the young folks and they wont believe you, no, no, no), I did work on modems and vehcice dectors using this principle.

So some of the common issues.
Faulty, broken or burnt out coils......so knowing what the resistance and inductance of the coil should be would be helpfull.

We had a lot of trouble with slop, wear and mechanical failure in the coils.
The coils on the boards would develop slop between the adjsuting slugs and the formers and cause random triggerings, drifting or instabilities.

In the case of coils in the roads, they would also develop problems.
We had to be particular about having the coils properly potted or glued into their slots, but beeing on a road there was always damage over time.

Insulation resistance and leakage in the both the on board inductors and the variables could cause problems.

So..although I have not worked on these golf cart controlls I would sugest the following.

have a real good inspection of the inductor its self....test the resistance of the coil compared with new.....measure the inductance of the coil compared with new....if you have the instruments..both with the slug in and out and varing about.


look for any play or slop, in the mounting and especially where the slug runs in the coil.

Be wary about contamination with oil grease or other carp.

Be consious of the routing and imobilisation of cables leading to the inductor.

I hope this helps.

cheers
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Old 01-31-2014, 05:47 PM   #8
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Default Re: How the ITS works is now known.

In both the modems and the vehicle decetors we had access to the circuits and we could observe waveforms...that was a very big help.

OH one other thing we had problems with was coupling and power supply filter caps.
I stripped down numerous vehicle dectors and replaced dodgy candy stripe capacitors and leaky electrolytics.

I doubt that component level access would be available in thiese units though.

cheers
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Old 01-31-2014, 06:06 PM   #9
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Default Re: How the ITS works is now known.

Are we looking at some reverse engineered products coming soon!?!?!
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Old 01-31-2014, 06:08 PM   #10
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Default Re: How the ITS works is now known.

Quote:
Originally Posted by radioman View Post
I measured the current draw of the ITS in my old golf cart to be 1.5 milliamps when the solenoid clicks and it increases up to 2 milliamps as the pedal is depressed as the cart begins to move. I double checked my reading on the Simpson 260 to be sure. That diagram of the ITS explains the resistance reading I was getting with the different meters and why resistance readings cannot be used alone to determine if an ITS is bad.
Did you read the info in the patent documentation that describes how it works?
There is also a schematic in there, showing all the components.

Looks like quiescent current is determined by the applied voltage. It also appears that the plunger moved by the throttle pedal is a critical part of the operation, since they describe it in the patent.

The way I read it, the mechanical sensing range is from 0.05" inside the tunnel to 0.9". Looks like there will be deadspace at both the top-end and bottom-end of the pedal stroke when it is adjusted right.

I tried it with a 1k in seris and could get a voltage reading, probably because the only 9V battery I had that was in use, wasn't very good. Still in the blister pack, but only 8.3V. I ended up just connecting the weak 9V battery through an ammeter without the resistor in series with the battery. I only got 0.55ma, but it went up to 0.87ma when I stuck a screwdriver in the hole.

Looking at the schematic, the input voltage only feeds the three IC's and a voltage divider that is set someplace between 27k and 47k, so connecting a 9V directly to it won't cook it. I'll see if a good 9V battery works better and then see what happens with higher voltage.

Nice to know it draws about 1.5ma at rest in the cart. That is what I'll shoot for on the bench.
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