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Old 02-03-2014, 07:56 PM   #21
radioman
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Default Re: How the ITS works is now known.

Left cart sit idle this afternoon after it wouldn't budge. Went to dinner and ran a brief check when I got home and it went into the herky-jerky mode. Temperature dropped to 65f. More info tomorrow if it don't rain. I was planning to scope across the ITS again to verify the AC component before the motor began drawing current to check that ripple component I measured last week is not influenced by current draw by the motor. This is an old golf cart I am testing and not one I depend on for transportation through the woods. But when it is working it has an impressive ability to pull fallen limbs or vehicles that won't crank to a battery charger location I don't think the PDS would pull. Suspect Curtis controller 25864G03. I recently retired and am bored with nothing else to troubleshoot.
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Old 02-04-2014, 08:35 AM   #22
JohnnieB
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Default Re: How the ITS works is now known.

That part number is a stock series controller. Model 1206, 36V, 275A. The attached is a block diagram for a 1204/5 controller, but the 1206 is roughly the same except that it uses an ITS type throttle.

The troubleshooting tree in the service manual that can be downloaded in the post linked to, is a bit cumbersome to follow, but the voltage readings are in it.
http://www.buggiesgonewild.com/elect...g-manuals.html

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Since the ITS sensor has an oscillator inside and feeds the coil AC, I suspect that is the ripple seen on the scope.
My guess that it was the PWM feed to the motor was before I know what was inside the ITS sensor.

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A series drive cart does have more towing abilities than a PDS, but not as much speed. However, a fast series drive cart or a PDS that can tow stuff, can be built. Some people have a fairly good idea about what they are going to use their cart for and buy one with a drive system that better suits their needs initially, while others use whatever they have already bought and may have to do more to meet their goals, or reach a compromise between dreams and reality.

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I retired nearly five years ago (May-09) and SWMBO (She Who Must Be Obeyed) retired a couple months later. We are best friends and share some hobbies, and being together 24 X 7 X 365 was something new and exciting, but eventually became routine. Marcia had her artwork and quilting to fall back to when the weather was too foul for outdoor photography and target shooting, and I had reloading, but once I had reloaded all the brass we had shot the previous summer, my brain cells started to turn to mush. Then I bought a golf cart and found this looney bin.

The technology used in electric golf carts dovetailed well with my prior skills and knowledge, but did I ever have a lot to learn about golf carts and I am still learning.
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Old 02-04-2014, 01:38 PM   #23
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Default Re: How the ITS works is now known.

JB: Thanks for the information. The temp dropped to the 50's today and it accelerates perfect. I am 99.9% the ITS is not the problem. There must be something intermittent in the controller affected by temperature. Something I want to try is bypassing the ITS substituting a resistor across the ITS connections to see if the controller would respond to a resistor. 12 volts I measured across the ITS and 1.3 milliamps through it works out to 9230 ohms equivalent resistance. Lower value resistors would make it accelerate. 6000 ohms would furnish 2 milliamps. I have a a box of miscellaneous resistors I will dig through and try fooling the controller into accelerating in few days. (R=E/I)
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Old 02-04-2014, 02:01 PM   #24
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Default Re: How the ITS works is now known.

There is an in-line connector between the pedal box and the controller that acts up when damp, so it might act up when the temperature changes. It is located in front of the batteries where the cable goes through the frame.
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Old 02-04-2014, 03:20 PM   #25
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Default Re: How the ITS works is now known.

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Originally Posted by JohnnieB View Post
There is an in-line connector between the pedal box and the controller that acts up when damp, so it might act up when the temperature changes. It is located in front of the batteries where the cable goes through the frame.
Thanks but I checked the continuity between the ITS white and black wires and on pins 1 and 2 on the controller. I measured the same voltage change I measured across the ITS when pedal depressed. Also got 36 volts on red wire on pin 4 and the reverse alarm would work when in reverse but it would not budge. I tapped on the controller to see if it would make it go and nothing. It is all working fine now without doing anything to make it go. I am going to leave it alone for now. Last time it went back to work it ran ok for weeks. Now that we have solved the mystery surrounding the ITS I feel more confident troubleshooting the thing. I will get the scope back out when the weather gets better and run some more test. If it ain't broke you can't fix it. I want to scope the M- output to the motor. I suppose I would need to connect the scope between B+ and M- on the controller.
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Old 02-04-2014, 05:30 PM   #26
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Default Re: How the ITS works is now known.

Quote:
Originally Posted by radioman View Post
I want to scope the M- output to the motor. I suppose I would need to connect the scope between B+ and M- on the controller.
M- is more positive than B-, so you will get a positive going waveshape.
The output at M- is PWM DC, ranging from 0% to 100% duty cycle.
PRF is in the 15kHz to 18kHz range.
When measured with a voltmeter, you have pack voltage at 0% duty cycle and close to zero at 100% duty cycle.
(Depending on the ampacity of the controller, when fully turned on, the MOSFETs drop from about 0.1V to about 0.5V per 100A of current flow through them.)

If you reference the scope to B+, it will be a negative going waveshape.
When a voltmeter is referenced top B+, you get 0V at 0% duty cycle and near pack voltage at 100% duty cycle.

Unless otherwise stipulated, all voltage measurements on a cart are referenced to B-.
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Old 02-05-2014, 09:23 PM   #27
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Default Re: How the ITS works is now known.

I wonder if this will yield the answer to a question I have about an old Logisystems 480amp controller I have. Due to them not labeling and then swapping spades plugs around with almost identical models... I burned the input resistor of the one that I bought years ago with no diagram. If I remember right the resistor was parallel to the two ITS input leads. The part was burned beyond reading but looked like a 1/4 watt blue bodied carbon resistor. Maybe one day I can fix this thing. I have an Alltrax now but it is just one of those aggravating things that it just sits in my garage unused.
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Old 02-06-2014, 07:37 AM   #28
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Default Re: How the ITS works is now known.

Quote:
Originally Posted by jonequest View Post
I wonder if this will yield the answer to a question I have about an old Logisystems 480amp controller I have. Due to them not labeling and then swapping spades plugs around with almost identical models... I burned the input resistor of the one that I bought years ago with no diagram. If I remember right the resistor was parallel to the two ITS input leads. The part was burned beyond reading but looked like a 1/4 watt blue bodied carbon resistor. Maybe one day I can fix this thing. I have an Alltrax now but it is just one of those aggravating things that it just sits in my garage unused.
It might have been a diode. Sometimes they take on the appearance of a burned carbon resistor if connected backwards.
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Old 02-06-2014, 07:49 AM   #29
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Default Re: How the ITS works is now known.

Quote:
Originally Posted by jonequest View Post
I wonder if this will yield the answer to a question I have about an old Logisystems 480amp controller I have. Due to them not labeling and then swapping spades plugs around with almost identical models... I burned the input resistor of the one that I bought years ago with no diagram. If I remember right the resistor was parallel to the two ITS input leads. The part was burned beyond reading but looked like a 1/4 watt blue bodied carbon resistor. Maybe one day I can fix this thing. I have an Alltrax now but it is just one of those aggravating things that it just sits in my garage unused.
It yields an answer, but probably not the one you are hoping for.

The bridge rectifier arrangement at the input of the ITS sensor routes the correct polarity voltage to the ICs on the PC Board no matter if the wires to it are connected +/- or -/+, so the two wires that connect the ITS sensor to the controller can be reversed without harming either the ITS sensor or the controller.

Therefore, pack voltage was applied to one of the ITS inputs on the controller due to either the KSI or 1/2 speed reverse wire being connected to it, which resulted in a high enough current flow to burn a 1/4 Watt resistor beyond recognition. However, the ITS source and/or sink circuits were also exposed to the pack voltage, so I suspect there is more extensive damage than just a burnt resistor.

The resistor between the ITS terminals on the controller is simply a shunt used to adjust the current flow through the external ITS sensor into the range needed by the current sensor inside the controller to produce a 0% to 100% throttle range.

Without the resistor installed, you should have a voltage between the to ITS terminals on the controller.
I so, install a resistor that will give you about 1.5 ma of current flow through the ITS sensor.
If no voltage is present, the ITS source is bad.

Even if you are able to get about 1.5 ma flowing through the ITS sensor, the ITS current sensing circuit in the controller may be bad, so it still won't work.

My guess is that more than just the resistor is bad.
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Old 02-06-2014, 09:40 AM   #30
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Default Re: How the ITS works is now known.

I totally agree with you. As a former elec. tech I knew that HV going into sensitive ITS inputs was way bad. I did change every IC chip I could on the board. I even put sockets for easy swap out in case one got popped in the bench testing process. The only "progress" I did have was when I made a little breadboard with spots to put random resistors and a couple of pots to play with varying impedance. When I hit a certain "sweet spot" the controller turned on full blast but that was as fine as I could get it. I always tell people that it takes hundreds or even thousands of components to make something work, but when it is broken it is usually just one $0.45 component that is bad..... Finding which one is why elec. techs exist.
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