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Thread: 2005 TBC...no trailer brake power until over 10mph Reply to Thread
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  Topic Review (Newest First)
06-02-2019 06:37 PM
rjranch You could try a switch hooked to 12v with a resistor so you could lower the voltage to want you might find at the trailer brakes and then hook the other side to the wire going to the brakes after the controller. You most likely would not want 12 volts back to the brakes because that would most likely just lock them up at that speed and cause more trouble than help. With a little experimenting with different resistors you can come up with a close voltage to apply but not lock the brakes. You may need to try this where it is safe so as not to have an accident if it is too much voltage, and you would want to measure the voltage to the brakes at a slower speed to get close to what you will need. This is how aftermarket units give lighter brakes at slow speed and more at higher speed inside the controller with the pendulum that tells what to apply. I shorted my wiring at the trailer in the past with 12v and it feed back into the controller and burned it out so another reason to stay away from 12v.
06-01-2019 11:06 AM
ZMANN i see references in the harness to BCM inputs and there will be a 0 chance we will find what info is coming over the BCM to the controller
05-31-2019 04:09 PM
Hydro Looking at that connector information, there is no speed input -- is the braking limit characteristic only active on certain model years?

I have not noticed any braking limitation below 10mph on my 2006 F250 -- but then again I will be noticing next time I have a trailer hooked

Need more information
05-31-2019 07:04 AM
djmaguire In looking at the connector, I can't really figure where a speed input comes into play. I'll attach the relevant section of the workshop manual. The connector is C2142.

Regarding my comments about logic gates and PLLs... I was only suggesting them as ways that - no matter what the speed signal would be - the signal would be automatically doubled/tripled/quadrupled in frequency.

An example of the logic gate way is this:



No matter the input frequency, the output frequency is doubled. In this way, if there is some other dependence on speed at higher speeds, it might be maintained. Might.

I wasn't suggesting that there was any problem with a fixed speed fooler circuit. I'm only saying that one that tracks speed and multiplies it might preserve some other modes of operations.

...but, again, I can't see a speed signal in the connector. So...
05-31-2019 06:11 AM
Hydro I suppose it depends on the origin of the signal used by the TBC -- may get it directly from the transmission speed sensor or from the buss system from the instrument cluster or PCM -- kinda need schematics to see the direction of the signal

The opto and timer setup would in the simplest form do what is needed and be user adjustable -- if the signal is direct

Maybe the signal is sent over the buss system -- then would need to isolate and modify the network messages -- an Arduino(Nano) or Raspberry(II) could work here and still be inexpensive
05-31-2019 03:42 AM
djmaguire
Quote:
Originally Posted by Hydro View Post
Could "fake" the speed input to the brake controller so it would think you were traveling over 15mph -- a fairly simple add on circuit to add pulses to the speed input -- could make it adjustable so you could choose the "gain"

Thinking an opto isolator circuit to eliminate feedback and a 555 timer to add the pulses
I haven't had a chance to dig in any docs, but I think that @Hydro is really going in a solid direction here.

Maybe the TBC was intended to not do much at low speeds. The attached doc suggests that. Then, it becomes a matter of preference.

@Hydro 's mention of the isolator and 555 timer to add pulses is a fine approach. There might be some irregularity in the timing, but the TBC wouldn't likely discern it.

A few logic gates could be used as a frequency doubler. A phased-locked loop (PLL) circuit could be used to multiply the frequency of the pulses by 3 or 4 times. Either would be a very clean way to do it since the actual pulse trian would be being "multiplied" resulting in stable/uniform pulse timing. Fun stuff.
05-30-2019 08:40 PM
Hydro Could "fake" the speed input to the brake controller so it would think you were traveling over 15mph -- a fairly simple add on circuit to add pulses to the speed input -- could make it adjustable so you could choose the "gain"

Thinking an opto isolator circuit to eliminate feedback and a 555 timer to add the pulses
05-30-2019 10:45 AM
iqraceworks
Quote:
Originally Posted by Mcflyfyter View Post
It's really not that big of a deal. If you want to slow down faster, just speed up a bit.
Great idea!
05-29-2019 06:00 PM
Mcflyfyter It's really not that big of a deal. If you want to slow down faster, just speed up a bit.
05-29-2019 05:17 PM
djmaguire You just need to mount one of these on the dash...



...and throw when needed.

Okay... okay... I'll look at what I've got.

_______________________________
Edited to add...
Wait. I have to read a 42-reply thread?!? There had better be some *really* insightful and inspirational stuff here. Like Confuscious-level shiite.
This thread has more than 10 replies. Click here to review the whole thread.

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