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I made an ABS triggering/flushing device

41K views 90 replies 35 participants last post by  Busabenny 
#1 · (Edited)
To make sure your ABS stays healthy, it is a good idea to activate your ABS system from time to time. It prevents the valves in the ABS to become sticky. Some people do this by regularly slamming the brakes on gravel, but I'm way too chicken for that. So I made a device that allows me to activate the ABS whilst the bike is stationary.



Another reason to have make this device is that I want to flush the brake fluid inside the ABS system. Internally in the system, there is fluid that never gets refreshed (behind the valves in the chamber that is pressurised by the ABS motor). After many years, this fluid will contain moisture, which can corrode the valves in the ABS, leading to a total ABS failure.

What does it do?
The device fools the motorcycle into thinking that it is moving at 30km/h. There are 2 buttons on the device: front and rear. When you push the button 'front', the device simulates a front wheel skid by stopping the signal to the motorcycle 5 times/second for 1/10th of a second.

How does it work?
When you push the button, the motorcycle will think that the front wheel is skidding, engage the ABS motor and close and open up the valves 10 times/second. If you push the button whilst the brake is applied, you will feel the pulsing of the ABS. If you push the button whilst the caliper bleeder is open, fluid will be pumped from the master cylinder reservoir through the ABS towards the caliper. This effectively flushes the entire brake system, including the ABS.

Now for the technical bits and pieces:
The V-Strom (DL650A K8 in my case) uses a 2 wire Bosch ABS sensor. The ECU provides the sensor with 12V, which goes to ground over a 80 Ohm resistor inside the ECU. The sensor has an internal magnetic field generator and logic to do auto-zero, so it only outputs a binary signal: high for no metal in front of the sensor, low for metal in front of the sensor (this is the metal from the sensor ring on the wheel). The result is a square wave of 50 HZ / wheel revolution with a high of 1,1V and a low of 0,56V.
Now there is two things that we can do if we want to simulate the signal of the sensor:
- either use a logic gate and 2 resistors to make a voltage divider, which we then hook up to the internal wiring on the motorcycle
- either simulate the sensor ring by providing an external magnetic field to the sensor.
I choose the second way, since it's much easier to just unscrew both wheel sensors than to dig into the bike to disconnect the sensors.
The magnetic field is generated by using a coil from an old relais. The coil is energised push/pull, which means that both wires are connected to a logical totem-pole output. In the "on" position output 1 is high and output 2 is low. In the "off" position this is reversed. This effectively creates a magnetic field that changes polarity, even though we only use a single 5V source as power supply. To couple the magnetic field to the sensor I had to experiment a bit. If you put the center of the coil up against the center of the sensor, it will not work. This saturates the sensor and it doesn't give any output. Increasing the distance a bit works, but this is a sensitive setup. What worked much better was to position the coil at 90 degrees to the sensor, with the coil just in front of the tip of the sensor. This solution works, but only in the plane perpendicular to the white extrusion on the sensor. In this orientation, the coil is probably aligned with the internal magnetic field of the sensor. In any case, in this orientation the coil can reliably excite the sensor.
To trigger the coils, I use an arduino with a simple timing based on the micros() function. The coils only pull 8mA, so there is no danger in overloading the ports.

If anyone is interested in replicating this device, I will make a video to explain how you can do this and I will post the code.
 
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#4 ·
Clever!

It's a good idea to make sure you know how how your ABS is going to react and how it feels. Last thing you want to do is be in an emergency situation and not know how the bike will react. Getting the rear to activate is easy, just step hard on the pedal. For the front try a quick grab/release of the brake lever on gravel or a bumpy piece of road. Even it it didn't work the bike won't fall over and if you do it enough you will grow confident in it's working.

..Tom
 
#5 ·
Patent that thing and start marketing it! Very cool!
 
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#11 ·
This.

Its a great tool for bleeding abs system and would be worth a lot of money. Get a patent before someone else makes a fortune off your idea and work.

(I do think its a good practice to test the system on dirt or gravel once in a while, just to see how it feels.)
 
#7 ·
This is a very timely thread. I recently flushed my hydraulics again and hoping to clear old juice out of the ABS unit I turned to my HealTech... Turns out that although the Suzuki tool will force run the ABS unit, the HealTech will not. Bummer. I asked HealTech support if I was simply missing something, but they confirmed that it is not a feature of their existing unit. They also mentioned that they are in the middle of refreshing their product line. I asked if the refresh would be a software / firmware update or if it will require new hardware, they answered new hardware. Another bummer... I made a few more suggestions for improvements and they said they will pass them along to the design team. It would be awesome if they also publish a software update for their existing hardware to include the ABS active test. If Suzuki's OBD system is anything like other car systems, forcing the ABS to run should be little more than figuring out the correct commands and then injecting them, so I would hope their current interface hardware is capable. Finger's crossed...

In the meantime, I'm stuck without a way to force the ABS to run. I thought about putting voltage to the pump motor and solenoids, but that is just too risky for me with so many unknowns and such a high replacement cost.

I had to do it the old school way of stabbing the brakes while riding across the circle several times. But there are several weaknesses to this approach... I don't know what the dead volume of the ABS pump is, nor do I know how big each nibble (pulse) is. So there is no way to know how much I need to lock up and activate the ABS unit to cycle out the fluid within it. Additionally, if I do it too much, wouldn't the ABS pump just ingest the majority of the same crappy fluid it just pushed out? I suppose that rotating it and diluting it a bit with the fresh is better than nothing.

I would much rather be able to force run the ABS while in the shop, if for no other reason than being able to purge by running the ABS with the bleed valve open (which can't be done by riding and stabbing the brakes).

You sir, are a genius! It is completely non-invasive to remove the wheel sensors and attach them to some, let's say, 3D printed gizmos that falsify input signals to get the ABS to trigger on its own... A couple of 555 timer chips and some coils, and ShaZam! Or an even lower tech approach of fastening a piece of metal to a small motor that spins it in front of the sensor. Getting the latter to work would depend on how tolerant the system is for confusing / bogus input signals. Although a sophisticated enough disc with some holes missing would fix any sloppy timing. Although getting the two discs to spin at close enough to the same speed (if that is even necessary) could be challenging. I suppose one could use the same disc with the sensors mounted on opposite ends, but that would required getting both sensors to meet in the middle of the bike, and the easy / non-invasive nature would be out the window...
 
#8 ·
Question

In the meantime, I'm stuck without a way to force the ABS to run. I thought about putting voltage to the pump motor and solenoids, but that is just too risky for me with so many unknowns and such a high replacement cost.
.
This is a question. Not a suggestion.
When you turn the key on, doesn't the system pump come up to pressure and then shut off when it checks okay?

If true and you had the bleeder hose open when the key is turned on _ would the pump not continue to pump?
 
#18 ·
I was in a hurry before, and should probably clarify my previous post...

1) In no way did I intend to disparage your ingenuity or efforts. It is a fantastic idea and good solid work.
2) I agree that electronic signaling is the best approach.
3) I would be at the front of the line of interested hobbyist and I think you are correct that there wouldn't be much interest commercially. However, don't discount the ABS unit replacement aspect. Regular replacement of the fluid is easy and probably doesn't require your gizmo; however, flushing air from a newly installed ABS unit would absolutely be a nightmare without it or an SDS.

The two main points of my previous post were first to clarify what I had envisioned with the mechanical option and to reiterate that there is more than one way to skin a cat. Second, even though I would be at the front of the line of interested parties, I'd bet that we are overthinking the need with regard to regular brake fluid flushes. I already have all the parts and equipment needed to prototype, test and fabricate an electronically triggered unit; however, there is a growing list of things with greater need that I can't seem to find the time for. For example... I should probably be out there flushing the black brake fluid from my wife's car and the rest of my fleet.
 
#21 ·
I'd bet that we are overthinking the need with regard to regular brake fluid flushes.
Haha, indeed. You hear about the 10 people that have a problem with their ABS, but not about the 100 people who don't have problems, even if half of them never does basic maintenance.
Thanks for the feedback, I guess the reward of tinkering with a solution is in the tinkering itself :)
 
#19 ·
Very cool idea and concept, however I activate my ABS on gravel "all the time", and it works amazingly well and without any drama, butt puckering or instability....don't be afraid to do it on occasion for the exact reason as to why the OP developed this solution. Of course this should be done on relatively flat surfaces, do not recommend on steeper declines. :)
 
#26 ·
So I made this video to demonstrate my device.
Feel free to share it on other forums. I'm trying to get an idea about how many people are interested in this.

https://www.youtube.com/watch?v=ifsJMZn01kU
EXCELLENT
One of the first questions the public will ask and in turn spark interest is:
Will it work on my bike?
Is it brand specific and or Bosch model #xxx specific?

I'll be happy to share it.
 
#32 ·
I would like to buy or make one of these devices. Great learning project too. Do you have instructions or a parts list?
Parts list:
1 arduino
2 12V relays (to use their coil, or just find 2 similar coils)
2 push buttons
4 meters of lamp cord
A power bank and usb cable to feed the Arduino.

Then program the arduino to give the correct number of pulses on the front and the back sensor to simulate 30 km/h.
Whilst the front push button is pushed, interrupt the signal to the front coil 5 times per second for 1/10th of a second. Do the same for the rear push button.
 
#35 ·
Here is a good YT video on How the ABS system works.

This diagram is essentially the same as the diagram in the Suzuki service manual. The video is a little misleading because it seems to show the brake fluid circulating or moving through the system which is never true unless you crack a caliper bleeder and release fluid but that only releases fluid in the primary circuit. Even activating the ABS (intentionally on dirt or using this device) the side circuit fluid is never replaced, it is just moving a tiny amount under high pressures within that circuit. This is a problem and as the OP mentioned, this configuration probably has a design life of around 10 years before the old fluid gums up the works. Of course, activating the ABS is still a good practice (mainly to exercise the solenoids/valves/motor) but I don't think it gets to the actual problem.

My first V-Strom was a Gen1 650 (ABS was an option from 2007-2009 and standard for 2011) and ABS failure/problems seemed to be exceedingly rare (other than sensor damage or failure). I swapped that for a Gen2 650 and it seems that ABS failure/problems are much more common based on posts here but that is pure speculation on my part. The ABS motor/valve was redesigned for the Gen2 650 (I don't know about Gen3) to reduce the weight and amps needed to operate the motor. In any case, I've been concerned about losing my ABS motor/valve so I recently bled the brakes. I bought the bike used (it is a 2014) and believe that the brake fluid had never been changed. After ~5 years, the front fluid looked fine but the rear fluid was much darker, like tea. I have since bled the rear twice more hoping to prevent a failure. One problem with the rear brake is the hoses run right next the to the 400F exhaust pipe which probably why the fluid looked dark as compared to the front. I wish there was a way to bleed the dead-end ABS motor circuit but I suspect that that might be very difficult without completely removing it and letting drain or some other method that I am not aware of. Lately I've been ending my rides on some dirt near my home and activating the ABS and plan on doing a couple of more bleeds to maximize my chance of avoiding a problem down the road.
 
#41 ·
Thank you for the additional details. Can you the correct number of pulses or is something we also have to figure out on our own? Vstrom abs ring diameters and number of slots? I would be happy to share what I come up with. Will any 12v relay work? What type did you use? I suppose I could experiment and share that as well. I understand your concern about debugging code. It's been many years since I have done it, but still remember the pain. Although maybe in this case my daughter and I can partner up.

Sent from my SM-G930V using Tapatalk
 
#43 ·
I did not know that fluid is trapped in the ABS chamber...interesting. I think many of us here would be interested in your device should you choose to market it. In this day and age I don't have much faith in a patent protecting your invention, so I say just build it and sell it.
 
#44 ·
No worries on the patent. It's not worth the effort and I'm not planning to become rich on something like this.

Regarding other bikes: yes, it will work, but the ratio of the front/rear wheel circumference will need to be adjusted. You could add a potentiometer to do that, but then people would need to look up in a cross-table of front/rear wheel tires what number they need to set the potentiometer to.
 
#46 ·
ABS Backflush

After looking at the video I posted in reply #35 and thinking about this for a bit I realized that it might be possible, using this Arduino device, to back flush the ABS module using the motor. In the attached diagram, normal brake bleeding drains fluid in the primary flow path from the reservoir at the top at the front lever and is released at the caliper at the bottom (shown with black arrows). The servo controlled valve at S1 is normally open and S2 is normally closed (i.e. normal = no ABS activation). When ABS activates S1 closes and S2 opens and the motor runs to pressurize the flow in the secondary path. If you connect a hose to the caliper bleeder and put it in a can of DO4 brake fluid, with the caliper bleeder open, the motor will draw fluid from the bottom can of fluid to the reservoir at the top (show with red arrows). At the top you'd have to have a master cylinder bleeder to release fluid or you could keep the reservoir empty using a syringe or turkey baster. (The rear brakes are essentially the same and probably more important to back flush due to the proximity to the rear exhaust as mentioned in my previous post).
 

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#47 ·
That is indeed how I think it works. I think that between M and S2 there is also a pressure chamber which is pressurised by the motor when the ABS is armed. When the ABS is activated, S1 closes to release the brake pressure. Once the wheel spins freely again, the system opens s2 and s1 to let the pressure from the chamber re-pressurise the caliper, whilst at the same time starting the motor to rebuild the pressure in the chamber. The reason for the presence of the chamber is that the motor takes a bit of time to build up pressure. The ABS needs the pressure to be available instantly (or at least < 0.1 sec), so it maintains the pressure in the chamber ready to use in case the ABS is activated.
When you use my device, you can feel this clearly: if you activate the ABS for more than a few seconds the motor can’t keep up and the pressure drops.
 
#48 ·
That is indeed how I think it works. I think that between M and S2 there is also a pressure chamber which is pressurized by the motor when the ABS is armed.
Some diagrams call that the accumulator whereas Suzuki's diagram calls that a "damper". I left it out of the diagram for simplicity and to focus on the bleed paths.

When the ABS is activated, S1 closes to release the brake pressure. Once the wheel spins freely again, the system opens s2 and s1 to let the pressure from the chamber re-pressurize the caliper, whilst at the same time starting the motor to rebuild the pressure in the chamber.
Actually its the opposite. The operation of the brake lever by the rider is pressurizing the fluid North of S1, to above M (there is a check valve), to below S2 (which is closed) thus activating the caliper and the brakes in normal operation. When wheel lock up is anticipated via the wheel sensors, S1 is activated to close it, taking the rider out of the loop but everything between S1, S2 and the caliper is still pressurized and trying to stop the wheel from spinning. If closing S1 is not enough to stop skidding you need to *lower* the pressure to the caliper. Opening S2 releases pressure from the caliper and the motor starts to pump fluid back to the reservoir at the master cylinder. So the motor is being used to *lower* the pressure in the damper (not shown) and the piping North of S2 to release the brakes. If the motor was pressurizing this path it would be activating the brake, the opposite of what is needed.

The reason for the presence of the chamber is that the motor takes a bit of time to build up pressure. The ABS needs the pressure to be available instantly (or at least < 0.1 sec), so it maintains the pressure in the chamber ready to use in case the ABS is activated.
You are correct that the damper (or chamber) is necessary so that when S2 is opened the calipers are released immediately and the ABS does not have to wait for the motor to get up to speed. But the motor is lowering the pressure in the damper not raising the pressure.

When you use my device, you can feel this clearly: if you activate the ABS for more than a few seconds the motor can’t keep up and the pressure drops.
The motor probably runs for a bit after S2 is closed so that the damper is at lower pressure and ready for the next use. Also there are probably check valves or relief valves built in so that the motor doesn't over pressurize the primary circuit or over de-pressurize the damper.

So question for you; When you run the ABS were you able to use the motor to draw fresh fluid from the caliper up to the master cylinder as shown in my diagram? That would be clear evidence of replacing the fluid in the secondary/motor flow path.
 
#49 ·
That a good explanation! I didn’t try to reverse bleed with the ABS motor yet, only from top to bottom (since this is the direction I thought the motor would pump). So now I know why that wasn’t working. I’ll have to try it in the other direction again, making sure the master cylinder reservoir doesn’t overflow.
 
#50 ·
dmfdmf
At the top you'd have to have a master cylinder bleeder to release fluid or you could keep the reservoir empty using a syringe or turkey baster.
For sanity, you might get a MC banjo bolt with a bleeder. Maybe even add a SpeedBleeder
 
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