Excessive Braking Effect

[malcolm_garrett]

Hi, one more issue I'm having!

Using Arc Pro my cars come to an abrupt stop as soon as I remove my finger from the controller trigger. There is no freewheeling at all like with my older analogue cars. This 'braking effect' negates any need to use the brake button (which now only seems necessary for pit stops). 

This braking effect is so strong that you have to keep a little pressure on the trigger non-stop or the cars immediately halt. This has resulted in cars flying into the back of other cars which have come to an unintended dead stop in front of them.

Anyone with similar experiences?

[Andy P.]

Are you in digital or analog mode (I am assuming digital because of you mentioning "rear-ending")?

What type of cars are they?

What brand what year?

Are you racing with magnets?

[Dr_C]

Malcolm is raising great questions, it will be interesting to learn more about how the ARC PRO applies braking... should we assume there is some form of dynamic braking designed into the ARC PRO firmware? Unless someone is able to share an answer... let's investigate further...

 

C

[woodcote]

These are great questions! From using ARC Pro and ARC Air, I am also assuming some form of dynamic braking - a small reverse current going to the motor when the trigger is released.

 

The brake button itself is an on/off switch, as in the previous Scalextric Sport Digital systems. However, from a peek in the communication protocols, it does look like there's scope for more varied braking responses - possibly with ARC compatible Slot.it controllers that have adjustable braking. It would be good if this switched off dynamic braking.

 

I do use the brake button with cars that I've removed the magnets from - just a very quick blip at the end of a straight. There's a sense that there is some dynamic braking with standard non-mag cars, but for cars with traction magnets and cars with high-torque motors (like the Sierra I built here) they do stop quite sharpish.

 

I find it a challenge to roll cars with magnets round my R1 hairpin - partly because they stop when I release the trigger and partly because there's little 'tail-out' drift - and I do find myself needing to keep some throttle through R2 esses. It's a different way of driving to the non-magnet cars. The Sierra really is tricky to drive, in part I need to learn to drive competely differently with the extra torque, but I presume my difficulties are compounded by the dynamic braking. Keeping a little throttle going does definitely help.

 

Malcolm - are you running cars with the traction magnets in them? And what cars are you using? Some are a bit more stuck down than others! For example, the BTCC Civics are rather more grippy than the MGs, VWs and BMW 125s as their traction magnets sit much closer to the rails on the track. All modern cars are very different beasts compared to the old Scalextric cars that had no magnets or much weaker ceramic magnets.

[Pault86]

Yes, how does actually ARC PRO implement and control braking? I don't see any way to turn it on and off as in the c7042 APB. As the figures show, dynamic braking is usually achieved by shorting the motor when you completely lift off the hand controller. A resistor in series with the motor when it is shorted can reduce the braking effect, this is not shown in the figures.

 

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[Pault86]

I made a post with pictures but it will take a day to come up.

 

Braking must be done by the chip, right? I know the pb can send a zero throttle signal down the rails to a particular car ID. Does the chip use that to short the motor, thereby causing braking? In the ARC PRO, is dynamic braking always enabled?

 

In the c7002 controller, pushing the brake button used to switch in an 18k ohm resistor the pb could sense to know to turn braking on. In the wireless controller the brake button appears to be just a switch whose state is read by the controller's logic board. 

 

In any event, once baking is activated - at either zero throttle or by brake button - the factors that affect braking are the motor and the gear ratio. Using an armature with more copper wound on it, using stronger magnets in the motor, or increasing the power angle - the point in the rotation of an armature at which a coil becomes energized - will all increase braking. The gear ratio effects braking because the faster the motor must turn while operating as a generator the greater the current flowing in the braking circuit. A car with 4:1 gearing - 4 turns of the pinion for each turn of the crown - will have more brakes than a car with 3:1 gearing, other factors equal.

 

Regardless of how SSD implements braking, once it is turned on only the car, itself, should influence how strong the braking effect is. 

[Pault86]

Been a long time, but I think we have a brake bit in the data sent down the rails, the chip would use that, not the throttle level, to initiate braking. Have to recall the data on the rails format.

[Dr_C]

Agree there is a brake bit in the data sent to the cars and that this is enabled by the power base when the brake button is pressed (both with SSD wired and wireless throttles). However, with the original C7030 6 car power base there was also the option of dynamic braking. Then, with SSDC there was/is the option of progressive braking which I understand rapidly toggles this brake bit. So the question remains... what is happening with the ARC PRO that causes the excessive braking effect reported by malcolm_garett...? is some form of dynamic braking implemented in the ARC PRO (i.e. setting of the brake bit automatically when easing off the throttle) or is it simply the effect of strong magnets causing rapid deceleration?

C

[malcolm_garrett]

Cheers everyone again, for your responses!

Malcolm - are you running cars with the traction magnets in them? And what cars are you using? 

 

I have only four digital cars at present: 

Two Ford Escort Mk1s (C3635 and 3592)

Two MGB's (C3270A and C3631)

All have 'reduced magnets' in them (I have snipped the ends off the regular bar magnets and glued them in their original position). There was a similar harsh braking effect before snipping the magnets, but I can't say that I have detected a significant change. 

It might be worth mentioning that the Digital Plugs are all brand new, coming direct from Hornby in a new batch (they were out of stock until March). The new plugs look different from the ones previously pictured on the Scalextric website, Amazon etc. which had a large cylindrical part on them, which is now absent. Maybe there is a difference / differences between them?

BTW do ideas and suggestions from this forun get considered when the App development team meet?

And if / when the App gets updated are there / will there be notifications here / elsewhere as to which issues have been addressed.

Thanks again everyone!

[Andy P.]

BTW do ideas and suggestions from this forun get considered when the App development team meet?

And if / when the App gets updated are there / will there be notifications here / elsewhere as to which issues have been addressed.

Yes one of the things I do constantly is funnel feedback to the respectvie parties.

There will always be an annoucment in the ARC forum when a new version arrives...

[woodcote]

Malcolm - all four of those cars you have are fitted with the slim can 'FF' motor. I don't have any cars with those, but I understand that they are quite 'punchy' - meaning they have more torque than the standard 'S-can' Mabuchi motors that are more common in Scalextric cars going back to the 1980s. More torque usually means more braking, so I am still leaning more towards the car than anything unusual in the ARC powerbase.

 

The rate at which a slot car car stops - 'braking' - will be influenced by weight, magnet strength, torque of the motor, gear ratio, plus any unwanted friction (eg tyres rubbing on the body shell, tight gear mesh etc).

 

You mention the new chips. They do handle power slightly differently than the older Scalextric chips. I have noticed my cars with the new chips give more power more quickly. I hadn't noticed any difference with braking, but will keep an eye on that the next time I'm on track.

[Dr_C]

My quick assessment of braking as applied across SSD power bases is as follow... (and as always I may be wrong):

 

BRAKING with the APB (C7042)

=========================

In digital mode there are three options for applying brakes:

1/ brake button only

2/ dynamic braking whereby brake is applied when throttle is fully released

3/ both (i.e brake button and dynamic braking enabled)

 

BRAKING with ARC AIR

===================

Analog cars exhibit combined brake button and dynamic braking.

Digital chipped cars (operating in analog mode) - neither braking mode causes a brakng effect but application of the brake button does over-ride throttle so vehicle coasts to a halt.

 

BRAKING with ARC PRO

===================

With the power base in analog mode - braking effects same as above for ARC AIR for both analog and digital chipped cars (the latter operating in analog mde of course).

With the power base in digital mode - digital chipped cars exhibit combined brake button and dynamic braking.

 

Do others concur with these above tentative observations?

 

Dr_C

ps I really like the on board control of brake lights on the new C8515 DPR chips (white and grey packaging)... they are ... great fun!!! :-)

[Pault86]

Yes, can't speak to ARC AIR but agree with APB and ARC PRO. I have not tried to use the brake button with an analog car on ARC PRO operating in analog mode. 😮 Tonight my track is under construction so can't test that but will in future. In digital mode, with both mag and no-mag cars, it "feels" as if ARC PRO enables dynamic braking by default, with no ability in the app to turn it off.

 

Malcolm seems to be seeing the problem with digital cars in digital mode, is that right, Malcolm?

 

Does the chip implement braking by shorting the motor as old style three-wire controllers would do, or does it apply a reverse polarity voltage to the motor? I have tried several types of cars, analog and digital with different vintage chips, and cannot reproduce the excessive braking effect. Braking by button braking does seem to stop the car more quickly than just lifting off the throttle but I haven't tried to measure that to confirm the perception.

[Pault86]

Okay, measured button braking verses lifting off the throttle for both analog cars in analog mode and digital cars in digital mode. Conclusion: no difference in braking between the button brake and lifting off the throttle.

 

Malcolm, have you tried testing your cars on a friend's track or testing a friend's cars on your track?

[Dr_C]

Ok, unless I am mistaken, I think Warren is observng the difference between setting the APB (C7042) to braking by button only and using the ARC PRO which is currently configured for brake button and dynamic braking combined. For the APB there are several modes, but brake button only would cause the car to coast when the throttle is released. In that mode the brake button causes sharp braking. With the ARC PRO the dynamic braking causes sharp braking whenever the throttle is released - exactly the same as when the APB is set to dynamic braking (unless SSDC or similar race management software is used via PC link to the APBin which case a form of braking modulation is used to achieve softer and progressive braking).

 

So how is braking achieved? First, it is important to be aware that a dc brushed motor can act as a motor or a generator depending on which way the power flows. If a dc brushed motor is set running and then the drive voltage is diconnected, the motor will start to behave as a generator and it will generate what is known as a back-EMF (where EMF stands for electromotive force). If the motor is open circuit, then no current flows and so no electrical power is generated. If however the motor is connected to a load resistor then the back-EMF causes current to flow so kinetic energy (rotational within the motor and linear via the forward motion of the vehicle) is converted into electrical energy... the loss of kinetic energy = braking effect.

 

In pure analog mode the above is achieved by creating a short circuit within the analog controller. In SSD this is achieved by the controller signalling to the in-car SSD chip to turn off the power drive transistor and then  to turn on a transistor which creates a short circuit across the motor.

 

So what is the answer to sharp braking in digital? I think we will need an upgrade to the ARC firmware and app in due course which gives us the choice of braking modes as we had with the APB...

 

Maybe one for the nice-to-have-please requests to Scalextric/Hornby for when the time comes for a firmware update and app revision?

 

C

 

[Pault86]

Thanks, Dr_C, for explaining how the chip implements braking!

Malcolm, I have not been able to duplicate the excessive braking problem. The one thing I have found that makes braking feel slightly different is changing the throttle profiles. When the throttle profile feeds voltage to the car more quickly - so the car accelerates more quickly - braking "feels" like it happens a little more quickly to me. The default throttle profile is Profile A, Profiles C, D, and E produce quicker accelaration and make braking feel a little more drastic to me.

Check and make sure you are using Profile A. Also, try running your cars and a friend's cars on both your track and another track and make a post to tell us what you see.

[-Magic-]

If help, here an info:

When you press the brake, I think that the controller send to Powerbase the brake input AND zeros the throttle (even if you press it). This is what I see and what I get from BLE protocol.

[Dr_C]

Yes, the BLE protocol shows the throttle data set to zero when the brake button is pressed, but it is not yet clear whether this zeroing function takes place in the controller itself or in the power base... I suspect the latter :-)

C

[Fatthinslim]

BTW do ideas and suggestions from this forun get considered when the App development team meet?

And if / when the App gets updated are there / will there be notifications here / elsewhere as to which issues have been addressed.

Yes one of the things I do constantly is funnel feedback to the respectvie parties.

There will always be an annoucment in the ARC forum when a new version arrives...

Hi , I have been reading this forum about the digital cars. The old analogue cars obviously depended on voltage loss hence the free coasting to a halt which had many benefits when racing the cars. The digital have a major flaw. Yes they act the same pulling away but because of digital information from throttle Controller on increase and decrease the motor will act accordingly .... would be great if the electronic engineers look into having a modification to allow ramp down for the controllers or in the chips on the cars.., so if ramp up signal loss have a timer chip or relay disconnect the motor feed to allow free coasting for a set time unless the brake button pressed or throttle increase made...., there must be a way

[Dr_C]

Yes, a simple firmware upgrade in the throttle controllers could help take care of this... brake should not be applied automatically within the throttle firmware when throttle trigger is fully released.

 

Then, the powerbase firmware could default to adding dynamic braking (i.e. brake applied when throttle signal is zero). However, a simple menu feature on the app could turn dynamc braking off or on.

 

Two very easy firmware upgrades and the job would be done :)

 

Could this be a possibilty for 2019 please?

 

C

[malcolm_garrett]

Yes, a simple firmware upgrade in the throttle controllers could help take care of this... brake should not be applied automatically within the throttle firmware when throttle trigger is fully released.

 

Then, the powerbase firmware could default to adding dynamic braking (i.e. brake applied when throttle signal is zero). However, a simple menu feature on the app could turn dynamc braking off or on.

 

Two very easy firmware upgrades and the job would be done :)

 

Could this be a possibilty for 2019 please?

 

C

 

[malcolm_garrett]

That would be fantastic!

[Fatthinslim]

I recently posted about the braking effect when letting go of throttle and have experimented a little. ...I took a controller apart and it only has a variable resistor and small pcb for brake and lane change.  I found when i rev a car and lift it of the track it free wheels, and the same effect can be achieved by not fully letting off throttle, so I found a position on the throttle at the point where the car wants to move but just sits there singing.....I measured the resistance of the variable resistor in the throttle in the desire position which was about 500ohms .(throttle range is between  4 ohm to 5k). I soldered a toggle switch with a 500ohm resistor in series with the white wire going to the variable resistor to fool the main controller in thinking it's never fully released with the option of switching back to normal...

Now when toggle switch is made the car will buzz when stationary just like adding a little throttle normally. Operate throttle through range is good, and when you just release throttle completely car freewheels quite nicely compared to braking and stopping giving more fun in corners and making you have to use the brake button , 

I'm going to mod the rest of my controllers as it is an improvement , hopefully though scalextric will come up with something more substantial ... 

[Dr_C]

Hi Fatthinslim,

 

Nice work... but I am surprised you found it necessary to use such a high value of resistor... something  around the 150 ohms, 180 ohms or 220 ohms should remove the dynamic brakng without causing the cars to humm... if the cars are hummng then their motors are being powered in a lightly stalled state with one of the windings carrying a fair bit of current.

 

 

500 ohms will put the throttle signal very close to the drive away threshold... and for magless drivng may even be enough to prevent the cars from coming to a stop at all. Might be worth trying resistance values lower than 500 ohms...

 

C

[John-347493]

I realize this is an old thread, but I came here to ask this same question after trying my new set for the first time yesterday. It really feels like the cars brake either by reversing the motor as they do in race centers with a third controller wire and/or the effect of the traction magnets. To me it seems the brake button really is only used to signal pit stops to ARC. I don't mind that, to be honest. I'm so accustomed to using just the throttle to drive / brake all these years I kind of prefer it. I wired my home HO track with three wires and the strong magnet cares stopped abruptly no matter what. It was fun with the non-magnet and T Jet cars.