marininn wrote:
BenK, i think they are talking about voltage, not ABS.
From what I surmise, the on and off pattern of the brake controller is not for ABS, I was not thinking that, but for voltage. Sounds like the brake controller puts out the full 12 volts, but when it cycles on and off quickly it roughly equates to a lower voltage. Am I correct here?
The PWM will simulate a constant voltage (RMS) and the inductance of
the magnet will smooth it some more (hysteresis)
So, 50% on 50% off time-wise yields a kind of dirty 6 volts (is what I assume). This happens too fast for the mechanical brakes to respond to, so the effect happens at the brake (the spring, pad and magnet).
See below comments and is the inertia/RMS voltage
If I understandโฆ The brakes are powered by the movement of the wheel. The brake drum rotates around the stationary brake pad. The magnet pushes the pad into the drum and friction pulls the pad, or wedges it almost, into the braking action. Compared to the electronics on the other end, this is a slow process.
Someone add to this as is all I understand so farโฆ
Yup, the inertia in comments below
Sorry, am also answering a PM thinking PWM'ing the signal to the
trailer is a form of ABS
ABS...Anti-Lock Braking System and is to keep the tires from skidding by
NOT holding their rotation at the point to skid
Not stopping rotation, just slow the rotation down enough to keep the
tires from skidding. This is part of what is meant by modulation of
the braking
Today's ABS will reduce the MC Hydraulic PSI sent to the calipers many
times per second...buzz them with reduced PSI and then back to high PSI
Pulses per second and as for how many per second you'll have to look that up
There is a rotation sensor on each wheel and is basically a gear toothed
ring, but many call it the tone ring
NOTE: this is why when changing tire rev's per mile...you must or should
tell the computer(s) of that change, as they do NOT really sense skid
but look up on their tables for 'that' tire's rev's per mile vs the
MPH you are going...AKA changing tire size/type/class/etc...gotta
tell (reprogram) the computer(s) to use a different look up table and
why some can NOT be reprogrammed...their DB does NOT have that tire's
rev's per mile listed...
Drum/shoe braking systems do NOT have the ability to set and release
the shoes from the drums that quickly, as it has to travel much farther
than a disc/pad system (actually, the pad just kisses the rotor at
all times)
So the pulsation frequency for drum/shoe setups are much lower in frequency
Since most drum/shoe braking systems has one shoe self wedging, ABS
does not work well, as since they are self wedging...they will NOT
release quick enough for true ABS to work well
Maybe with a magnetic based shoe, it can be pulsated to simulate a
rudimentary ABS of sorts...but then the impedance of the magnets
would then become a factor on how fast they can be pulsated. The raising
and falling flux field would have too much inertia (impedance) to be
an effective ABS braking system
Then add in the known for most trailer OEM's NOT using the best practices
for their brake wiring, there are those impedance's from too small
a wire gauge, poor connectors and poor routing
If the tire continues to skid or approach skidding, the ABS computer will
continue to increase the pulse cycles to reduce the amount of braking
Why I don't really like ABS for 'me', as I can modulate my brake system
better than any of the ABS system on my vehicles
The PWM (Pulse With Modulation) of the IBC signal to the trailer is
just a form of controlling the signal. Instead of a steady voltage
signal. Simplistic explanation, but won't go into that technology here
Think that is the confusion thinking IBC's will ABS the trailer brakes
True ABS system for the trailer will require a tone ring (that ABS
sensor) on each trailer brake wheel/tire. There should be mention of
a 5th ABS channel (along with a disable or feature where it senses
whether there is a ABS equipped trailer)
Otherwise, it just buzz's (PWM) the signal. Think the frequency is set and
the amplitude (voltage) is variable, but am not sure and maybe they
do have the ability to change the PWM frequency
-Ben
Picture of my rig1996 GMC SLT Suburban 3/4 ton K3500/7.4L/4:1/+150Kmiles orig owner...
1980 Chevy Silverado C10/long bed/"BUILT" 5.7L/3:73/1 ton helper springs/+329Kmiles, bought it from dad...
1998 Mazda B2500 (1/2 ton) pickup, 2nd owner...
Praise Dyno Brake equiped and all have "nose bleed" braking!
Previous trucks/offroaders: 40's Jeep restored in mid 60's / 69 DuneBuggy (approx +1K lb: VW pan/200hpCorvair: eng, cam, dual carb'w velocity stacks'n 18" runners, 4spd transaxle) made myself from ground up / 1970 Toyota FJ40 / 1973 K5 Blazer (2dr Tahoe, 1 ton axles front/rear, +255K miles when sold it)...
Sold the boat (looking for another): Trophy with twin 150's...
51 cylinders in household, what's yours?...