Jeff in TD

Actually, I kind of wondered but couldn't find info on what type of controller the stock system is.

I've had pendulum type, and once adjusted they work pretty well, but once I got a Brakesmart I was really amazed at how much better it works.

If the factory ones are fluid sensing, great. If not, when it is time for a new truck I'd be interested to know if the factory controller could be unplugged so I could install a Brakesmart.


As far as someone making an open source design with parts list or a kit, I'd imagine liability insurance and whatever DOT certification and testing costs may be a death nail to smaller brake controller companies.


On a side note, I always thought it would be neat if Brakesmart or Maxbrake made a controller moulded into a replacement housing for the upper half of the column cover. It would be easy to see, clean and factory looking, and could have a lever for manual trailer brake application that would be handier.

6.7L MegaCab

The factory controllers are basic. They plug in using two connectors. You also get feedback from the EVIC, if it is enabled by the dealer or someone with a scan tool that offers that capability - I enabled it on my truck using AutoEnginuity. DIY kits would be just that - DIY. Gov can only control so much. Liability insurance is required in most states anyhow. Like nearly all Open Source/DIY kits, using it would be at your own risk. It would be ideal if MaxBrake or Brakesmart would just enter the scene again.

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Jeff in TD

Yeah that's kinda what I meant- maybe a DYI kit would avoid some certification headache.

I was kind of hoping the factory controller still plugged in to the same type connector, as it would make wiring simple for Dodge, and would make using something else easier for me.

j_martin

The main problem I see with a pendulum controller is that they have to be set to slightly apply the trailer brakes to keep the hitch stretched before the tow vehicle begins breaking. That's what they do. The photo below is what happens when they do that on glare ice. My son topped a hill in Montana, saw stopped traffic ahead, touched the brakes and the trailer launched into oncoming traffic.

On my first gen, the hydraulic actuated controller works great. If I need more axles, a simple emitter follower amplifier circuit will drive additional axles off the master signal.

If you feel the abs action in the pedal, a hydraulic sensor will also feel it. The electronics would have to take that into account, which isn't hard at all. (integrator circuit, or logic) A high pressure sensor would likely be piezoelectric, which should handle the shaking with no problem Cost for a good sensor is quite high.

The world needs a good open source programmable controller for sure.

Homestead

Latest and greatest is the Direclink. Plugs into your OBD II port under the dash and the computer in your truck runs it.

I recently sold my 02 Ram and bought a Chevy gasser and instead of putting the Brakesmart into it, I bought this unit.

I haven't installed it yet but have driven a couple of trucks that do have it and same as the Brakesmart, you don't know the trailer is there.

About the same price as the Brakesmart. Do a search on YouTube, tons of stuff there.

I found out about it from a converter of Class 8 trucks into RV Haulers, it is all they use after the Brakesmart/Maxbrake units went away.

Jeff

6.7L MegaCab

The problem with Direclink is that you can't use it and a programmer or digital gauges that requires the use of the OBD port at the same time.

I'm sold on the open source brake controller.

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Homestead

Shouldn't be an issue..........................


Jeff

6.7L MegaCab

I'm familiar with those, but the problem is having the data stream be 100% reliable. As far as I know, there isn't a splitter out there that will guarantee a dual connection. The last thing anyone needs is for the direclink to lose a connection because of a virtual fight over a tuner or gauges and that system causing a potential failure of the trailer brakes.

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icesoft

With one of my trucks that runs the MaxBrake currently torn down, I pulled the brake controller apart to reverse engineer it. I see some room for improvement, and have thought about producing a brake controller with a smaller footprint. My biggest concern comes in the form of insurance and liability if I were to sell it as a product.

Pressure sensors can be had for cheap if you look at the right sources. The last revision of the MaxBrake controller used an expensive Honeywell MLH series sensor, going price is about $120/ea (<$100/ea in quantity) for them which is the majority of the BOM cost on these units. I'm looking at the OE Chevy pressure sensors, they can be found for under $50/ea, and they're available almost anywhere.

When you're looking at the pressure sensor being 1/3 the cost of the unit (in the case of the MaxBrake), then adding the LCD display, custom molded case, PC board, IC's, cables, connectors, etc, there's not much margin left in the product. I guess I can't blame the guy for getting out of it, especially with the headache of 'User Errors' and such.

Biggest issue I'd had out of the MaxBrake is the pressure sensor cable being poorly constructed. The sensor uses 4 wires of an 8-wire Ethernet cable, the remaining 4 wires are used for production programming and debugging. Those wires became shorted together on mine and caused the screen to become unreadable. All they had to do was trim the remaining 4 wires at different lengths before putting the heat shrink on it... Had this problem with 2 of the 3 that I own/use. 1st generation controllers also had a problem with heat sensitivity on the pressure transducer, causing it to apply the trailer brakes if the engine bay got hot (with no user input).

The other hurdle in 'rolling my own' to sell, would be any patent infringement issues.

paylesspizzaman

Not sure if you guys are still interested in a diy trailer brake controller, but I've been tinkering around with one for about a year now. The latest version uses an Arduino Nano and pressure sensor. I've been having trouble with mosfets overheating though. I gave up for a while, but I'm going to get back to it next time I'm off. If anyone knows what might fix the mosfet problem, feel free to speak up.

j_martin

Don't know how you're driving the mosfets. PWM with decent rise and fall times should limit the dissipation.

icesoft

Too many unknowns to make any conclusions.

What MOSFETs are you using, what's the topology, MOSFET drivers, RDSon of the MOSFETs, etc... If PWM, what's the base frequency? Most TBC's run around 400Hz (and I'm sure someone came up with that frequency for a reason).

What's your testing setup? Are you driving an inductive load (as the actual trailer will be)? If so, do you have an external freewheeling diode to deal with the back-EMF generated from the brake magnets (should be connected from the output to ground)? The body diodes of the MOSFETs are usually not enough to deal with the abuse of driving trailer brakes and will increase the 'waste-heat' generated within the MOSFETs (especially the repetitive nature of PWM'ing them)....

Like j_martin said, quick rise and fall times are essential to keeping the internal power dissipation low, as MOSFETs usually are best used when switched fully on and fully off... Keep the operation in the 'linear' region to an absolute minimum.

paylesspizzaman

I am using an fqp47p06 Mosfet. Originally I started with 10kHz PWM, but had to redesign due to the heating problem, and also because of too much temperature instability with my circuit. After that, I decided to use Adruino for control. I tried 490Hz and 245Hz or whatever the slower output is. I am using a base biased 2N3904 bjt to pull the mosfet gate low and a resistor to drive it back high when the bjt is off. I don't remember the value of the resistor, but I think I chose something to flow about 100mA. I also used part of a 50A bridge rectifier as a freewheel diode, which does help with the heat. The heat is basically just split between the rectifier and mosfet. I feel like the whole thing still disapates too much heat. The cheapo off the shelf controllers don't seem to even get warm. I opened one of cheapos up to see if I could get a clue how they do it, but it looks like just the mosfets and freewheel diode. I will say they are using two 50A mosfets and they are oddly enough N-type. I was thinking of doubling mine up and seeing what happens.

paylesspizzaman

Also, I am doing on the vehicle testing with the actual trailer intended to be used.

icesoft

Yeah, 10khz is likely way too fast for the application, spending too much time switching, and not enough time carrying any current.

You would probably be better off using an N-channel MOSFET (like FDPF041N06 with an RDSon of ~4.1mOhm) and a gate driver IC like an LT1910 or LT1154 (I think I was going to use the LT1154). These IC's have the necessary charge-pump built in to drive the gate above the drain to turn the N-channel MOSFET on. It's not about the current to turn the MOSFET on/off (your 100ma), its more of a capacitive charge (field effect) that you build up on the gate (current does not actually flow through the gate to another pin like it does in a BJT).

I presume you chose the P-channel route as they look easier to drive from the outset, see this application note for the reasons you might want to change your mind http://www.onsemi.com/pub_link/Collateral/AND9093-D.PDF

I've also stepped away from my project for a while (too many other, more important projects going on to work on it). Having just stumbled into another MaxBrake unit, there's no real rush to complete it anymore. I was going to use a PIC microcontroller and the pressure sensor off of a Chevy Silverado's integrated brake controller, as they'd be readily available for the end user if/when they failed. My design is somewhat reverse engineered from the MaxBrake design, of which I have 3 controllers now (all 3 of which are different internally). The last one I had open to reverse engineer and repair, used a MicroChip TC7662 charge-pump IC and a IR2110 MOSFET driver (the charge-pump had failed, and I had to replace it.) I'd prefer a single chip solution for this purpose, like the aforementioned LT1154.