Factory brake controller

[GCroyle]

I am not wondering about anything. I understand how PWM works and how RMS or other type meters work, most do not.

OK If I'm trying diagnostics on a ITBC rig with PWM how would you use a basic meter with frequency setting to read the brake line circuit? How to interpret?

 

[SnoKing]

You Don't! You need something like a O-scope that will display the wave form.

Today coming Grants Pass, Or heading West on 191 doing around 45 mph I had a stop light change on me at the point I could not continue on and stopping meant throwing out the anchor. The 8k TT and 8500+ truck dogged right down to a nice clean stop with EH-6 setting. I think being a new 2019 trailer with whatever brakes come on 4400 lb axles was the difference. The Ram controller does NOT like marginal brakes, will NOT cover for them.

 

[Dan_69GTX]

OK If I'm trying diagnostics on a ITBC rig with PWM how would you use a basic meter with frequency setting to read the brake line circuit? How to interpret?

Well, there isn't an easy answer to that. The frequency setting would show you what the frequency of the pulse is. The problem is what is the frequency supposed to be? I don't recall seeing that on the CD manual.

Using a scope will show you the wave form - but again - do you KNOW what it is suppose to look like? If not, seeing the waveform is useless! A scope can NOT accurately measure the voltage or current - kinda like using a tape measure to read down to the .001".

Now, comparing waveforms or frequencies between a KNOWN working and the UNknown will help you diagnose. But again, you MUST be comparing IDENTICAL things - or you have thrown in another unknown.

As sag has already stated - you can do the basics of what you want with a blower motor - the faster it runs, the more total voltage and AMPS you are allowing.

Folks keep saying about the voltage they see - that is helpful, but means diddly. You need the CURRENT (amps) to make something work.

So you really wanna be accurate - measure current AND voltage. A bad connection / small wire can give you voltage but not enough current.

That is why folks do a voltage drop test - how much does the voltage drop from one end to the other.
https://www.aa1car.com/library/voltage_drop_testing.htm

Sorry, I've not done any testing on my truck to help - but I don't have a heavy trailer with 3 axles.

So - basic troubleshooting. Start with listing the knowns. What are the unknowns. All tests must only have one unknown (or variable in the equation), or - what are you testing for?!? Think back to your math classes - always try to get the unknown to one side of the equation to actually solve the equation.

Hopefully this helps you work on diagnosing this problem.

What jhenderson did regarding regarding recording voltage while the truck is plugged in, is right on the money. Test with the load attached (in this case, the trailer). IF you wanna see the waveform, amperage, etc - do the same.

 

[Wiredawg]

Well, there isn't an easy answer to that. The frequency setting would show you what the frequency of the pulse is. The problem is what is the frequency supposed to be? I don't recall seeing that on the CD manual.

Using a scope will show you the wave form - but again - do you KNOW what it is suppose to look like? If not, seeing the waveform is useless! A scope can NOT accurately measure the voltage or current - kinda like using a tape measure to read down to the .001".

Now, comparing waveforms or frequencies between a KNOWN working and the UNknown will help you diagnose. But again, you MUST be comparing IDENTICAL things - or you have thrown in another unknown.

As sag has already stated - you can do the basics of what you want with a blower motor - the faster it runs, the more total voltage and AMPS you are allowing.

Folks keep saying about the voltage they see - that is helpful, but means diddly. You need the CURRENT (amps) to make something work.

So you really wanna be accurate - measure current AND voltage. A bad connection / small wire can give you voltage but not enough current.

That is why folks do a voltage drop test - how much does the voltage drop from one end to the other.
https://www.aa1car.com/library/voltage_drop_testing.htm

Sorry, I've not done any testing on my truck to help - but I don't have a heavy trailer with 3 axles.

So - basic troubleshooting. Start with listing the knowns. What are the unknowns. All tests must only have one unknown (or variable in the equation), or - what are you testing for?!? Think back to your math classes - always try to get the unknown to one side of the equation to actually solve the equation.

Hopefully this helps you work on diagnosing this problem.

What jhenderson did regarding regarding recording voltage while the truck is plugged in, is right on the money. Test with the load attached (in this case, the trailer). IF you wanna see the waveform, amperage, etc - do the same.

You hit the nail on the head about not having known factory voltage output data specs. No wonder FCA techs have a problem evaluating using a 12vdc light. Bright, less bright, dim not very technical.

This has been my frustration is having to baseline working ones to evaluate ones not performing.

Ron

 

[SnoKing]

Dan, they are a couple things wrong in you post above. The O-scope does display the voltage. Second thing is E=IR which is Olms law, and can be stated as I=E/R. I is current/amps, E is Voltage, and R is Resistance.

So if the resistance of the four magnets is lets say 2 Olms and voltage is 7.8 Volts, then current will be 3.9 amps. The measurement of volts would have to be taken close to the magnets to be acturate. In fact measuring there and also at the outpuf of the controller would allow one to compute the amount of current lost in the wiring run.

If you read one of my earlier post where I talked about rewiring a trailer in a star configuration with #12 wire, that greatly reduced to wiring loss.

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points

My first training in electronics was in the USCG 6 month A school, and it began with resistors and Olms law, which is the basic building block of electricity/electronics. BTW: Former ET1(E6) 1965-69.

SnoKing

 

[SnoKing]

Also to learn more about meters Google RMS voltage.

https://www.google.com/search?q=rms...droid-samsung&sourceid=chrome-mobile&ie=UTF-8

 

[Dan_69GTX]

Dan, they are a couple things wrong in you post above. The O-scope does display the voltage. ......
SnoKing

Snoking- please show me where I said the scope doesn't measure/display voltage? I said it isn't ACCURATE - you want accuracy - get the fluke out. If you want to read Fluke corps stance that says what I stated:
https://www.fluke.com/en-us/learn/b...pes/comparing-a-multimeter-to-an-oscilloscope

.... Second thing is E=IR which is Olms law, and can be stated as I=E/R. I is current/amps, E is Voltage, and R is Resistance.
SnoKing

Hmmm - I reread my post and I still didn't see the word "ohm" or "resistance" in it. I only mentioned voltage and amperage. So, you already know the resistance since you have the knowledge of Ohms law.

So if the resistance of the four magnets is lets say 2 Olms and voltage is 7.8 Volts, then current will be 3.9 amps. The measurement of volts would have to be taken close to the magnets to be acturate. In fact measuring there and also at the outpuf of the controller would allow one to compute the amount of current lost in the wiring run.
SnoKing

Thanks for verifying my statement that one should do a voltage drop test.

 

[SnoKing]

You hit the nail on the head about not having known factory voltage output data specs. No wonder FCA techs have a problem evaluating using a 12vdc light. Bright, less bright, dim not very technical.

This has been my frustration is having to baseline working ones to evaluate ones not performing.

Ron

My guess is that most tech's do not know that it is a PWM output from the controller.

 

[GCroyle]

As sag has already stated - you can do the basics of what you want with a blower motor - the faster it runs, the more total voltage and AMPS you are allowing.

Folks keep saying about the voltage they see - that is helpful, but means diddly. You need the CURRENT (amps) to make something work.

So you really wanna be accurate - measure current AND voltage. A bad connection / small wire can give you voltage but not enough current.

This continues to be a very interesting discussion and measuring CURRENT and VOLTAGE in a live system is exactly the tool that I made.

And I*E=Watts and Watts is energy right?

 

[Wiredawg]

My guess is that most tech's do not know that it is a PWM output from the controller.

Exactly. Its disheartening when a company sells technology that it can't sustain or maintain.

Cheers Ron

 

[SnoKing]

"Snoking- please show me where I said the scope doesn't measure/display voltage? I said it isn't ACCURATE - you want accuracy - get the fluke out. If you want to read Fluke corps stance that says what I stated:"

Fluke makes nice equipment, but it takes a O-scope to truly see and understand the wave form, any distortions, noise or droops in the signal. And yes they accurately display voltage.

 

[SnoKing]

This continues to be a very interesting discussion and measuring CURRENT and VOLTAGE in a live system is exactly the tool that I made.

And I*E=Watts and Watts is energy right?

Watts are technically defined as "power"

 

[Dan_69GTX]

"Fluke makes nice equipment, but it takes a O-scope to truly see and understand the wave form, any distortions, noise or droops in the signal.

Totally agree.

"And yes they accurately display voltage.

We will just have to agree to disagree. - or we (and the Fluke Corporation) have a different opinion on what we define as accurate.

 

[SnoKing]

Totally agree.



We will just have to agree to disagree. - or we (and the Fluke Corporation) have a different opinion on what we define as accurate.

These two items can not both be true at the same time. Meters average "things", you understand what RMS is right?

The electrical engineer is going to want to look at the wave form.

 

[GCroyle]

Watts are technically defined as "power"

Correction accepted, thanks.

 

[SnoKing]

Dan, I just took time to read your Fluke link, I am having internet connection issues, and my take away is the opposite of yours. We are talking about a PWM signal, which is a wave form signal, and the pulse width should widen as the valleys narrow as the controller increases braking. As I noted RAM is using PWM on lighting also. Think dimming dash, and interior lighting.

If I was using Fluke on this issue, it would be the SCC290

https://www.fluke-direct.com/produc...YHxm94eWa-7IUv6-fj6JcK7i_6ooYc3xoC3wEQAvD_BwE

 

[PBJ2500CTD]

These two items can not both be true at the same time. Meters average "things", you understand what RMS is right?

The electrical engineer is going to want to look at the wave form.

Speaking of "average", the PWM signal from the brake controller should be read as average voltage, DC. It is the duty cycle and frequency that is controlling the output voltage. Can't really compare pulsed DC to RMS.

 

[SnoKing]

What would be very interesting would to have a 2014 and 2015 side by side to look at the difference, as 2015 is when RAM screwed up the controller. Some of us several years ago file complaint of safercars.gov.

 

[Dan_69GTX]

These two items can not both be true at the same time. Meters average "things", you understand what RMS is right?

The electrical engineer is going to want to look at the wave form.

Ummm - you are now changing the point of view of the discussion. I'm done.

 

[SnoKing]

Speaking of "average", the PWM signal from the brake controller should be read as average voltage, DC. It is the duty cycle and frequency that is controlling the output voltage. Can't really compare pulsed DC to RMS.

There are meters that would help, However they are not your grandfather's VOM or box store meters.