Great insight, Richard

As I recall, I got 4.8 kohm on the one throttle I measured - the good thing is that this can me measured with a cheapo multitester (not like say arm resistance)
But can you imagine using the throttle as is in a competition ?

Of course, this is tied to the fact that in the SSD throttle resistance increases with the speed command - for my project, I'm planning to retain SSD throttles, but using the other contact on the resistor (so that resistance decreases with trigger travel - the way God meant it to be)

Beppe

P.S. : could this - PWM never at 100% - be tied to decoder (and possibly motor) overheating ?

 

The PWM components in the car (am still not sure if they are Mosfets or Transistors) only dissipate power when they are switching.

So yes never getting to 100% will increase heat. That said it is only an issue on the straights, the rest of the time you will be at less than 100% anyway.

So the longer the straights the more you will miss the performance and the more it will have a heating effect.

If the Controller uses Transistors rather than Mosfets that is a bigger issue, in terms of generating heat!

They are shown as P03 & N02. Trouble is I can find both Transistors & Mosfets with this designation.

Richard

 

In my experience thus far, full throttle on SSD is rarely needed. You'd need a club raceway with a long straight to be able to make proper use of it, in the more confined spaces of the home track we might only get near it for a split second a lap. On our track the only people using full throttle are little so-and-sos trying to destroy my scenery or make the Audis do that nice roof spin they do when they turn upside down...!

In fact I've restricted the travel on one of the throttles, for use by younger drivers, and today a 6 year old won a race using this throttle, racing against two adults with standard throttles who just kept coming off the track. The 6 year old still came off but not as often as the adults who seemed to be put under pressure by seeing Junior's name consistently at the top of the standings on Bernd's RMS screen..!

 

Afterthoughts :

1 ) Imagine Wankel's scathing comment if he reads this thread !

2 ) 64 speed steps are way too many - most aftermarket electronic controllers have about a dozen, definitely no need to exceed 16. Now, could it be that the standard SSD response curve is such that you get 100% available voltage well in advance of 3F ?

Beppe

 

Nope, if you read the post, again, my 35 Hex controller only puts the motor on for 4/5 of the time. It needs 3F for full voltage.

 

HI, I HAVE BEEN READING ALL THE INFO ON POWER LOSS, ITS REAL INTERESTING, BUT I HAVE ONE GOAL ONLY;

I HAVE CONVERTED MY RALLY TRACK TO DIGITAL AND IT IS BORINGLY SLOW

, I WANT MORE POWER TO GET THE ARSE OUT ON THOSE CORNERS! LIKE THE GOOD OLD SPORT DAYS (LAST MONTH!)

CAN ANY ONE TELL ME HOW TO GET MORE JUICE TO THE WHEELS, OR BETTER STILL CAN I PAY SOME ONE TO DO IT FOR ME

 

Have you added the second PSU?

Have you tried an aftermarket PSU and wound the volts up?

Or are you too busy trying to fix the caps Lock on your keyboard?

 

Lol, Charming!

I am using a second PSU, and have wired "Booster cables" in three places.

What sort of voltage can i up it to using a diiferent PSU, without damaging the Base or causing other probs?

Gotta go to work now so i will pick this up later

 

My tests have shown that 13.5V seems to be reliable with no overloads. I think that other people have also tested, am not sure what they have found.

 

QUOTE (RichG @ 2 May 2005, 21:19)My throttle that only gets to Hex 35 puts the motor on for 4/5 of the time and off for 1/5 of the time.
So what can we do about this?

I am not sure.

Squeezing harder does not work and if you disassemble the throttle and move by hand the slider up the track a bit more you cannot increase the resistance.

The obvious thing would be to put another resistor in series. However this would create another problem, the car starts to move when the resistance gets to 0.3K, so if we tweaked to get Max throttle we would mess up Min Throttle.

So sorry to raise a problem and then not have a solution. You could of course sort the throttles and pair them with cars to even out some performance differences.

Would be interested to hear what values other people have and of any proposed solutions.
<{POST_SNAPBACK}>

Richard,

I also find the brake button kind of useless - if it had adjustable button brakes - yeah maybe, but using a button brake is kind of counter-intuitive, if you come into a corner and hit the (button) brake, you then forget to back off on the throttle, so as soon as you release the brake (which you do pretty quickly, cos it just stops the car too damn fast) you end up spinning out on the corner anyway...

sooo...

could you measure what resistance youre getting at full throttle (for each individual controler) and then swap out the resistor on the button brake to a resistor that gives you full throttle - either by adding button accelerator to your full throttle on the trigger (say the controller you are working on gives 4k at full throttle position, you would then make the resistor on the brake button 1k,) so then when u have full throttle position AND you hit the brake button, it gives u a burst of REAL full throttle..

thinking about it, if you did this, pressing the brake button alone would give you a preset low speed, useful for pits etc. maybe?...

Otherwise you could somehow rig up the complimentary resistor (again, if full throttle position gives you 4k, then the complimentary resistor would have to be 1k) so that it switches inline as soon as you touch the throttle? I realise that you wouldnt then have really low speeds - but do you ever go THAT slow?? if you were to have the 1k resistor in line all the time then you wouldnt have any zero throttle, so the cars would never stop.

does any of that make sense or am i missing the point?... if so - sorry

Alternatively - is there any way of pulling out the stock 5k resistor and replacing it with a more accurate one??

 

Hi, Yes good ideas.

The brake button one would work. I also agree with you that using the Brake button as designed is counter intuitive, and I never use it. I have always liked and used throttle off dynamic braking. (good job the road car does not work like that though!)

My problem with your solution is that it is still slightly awkward, and something else to remember to do. Mabe ok on a club track with a long straight but I would prefer the controller to work as designed.

In the Brake buttons defense, using it to allow max throttle on the start line, the releasing for a fast getaway makes some sense, but I can live without it.

Having the control jump from 0 to 1K would work but I cannot see a way of doing that.

The best solution as you sugest is to replace the resistor, would not matter even if this was 6K, that would just give a greater area of max throttle. I have not looked but I think it would be difficult to find a drop in replacement, also slider resistors tend to only be available in a small range of values.

If these are 5K 10% resistors then this was an accident waiting to happen, you just need to find some that are +10%

No, yet again what we really need is a small change to the code in the Powerbase to make 30 be max throttle and all is solved (as has been said 64 steps is more than is necessary), but unfortunately it cannot be upgraded!

Richard

 

I guess the best changes would be in the powerbase, but really they should use a lower voltage as 3F at the AD stage. Better still - you should be able to calibrate each throttle (as you can do in windows with cheap joysticks) - pull the trigger and say 'THIS voltage is max'...

maybe in the next release...

In the mean time - Maybe an extra butto next to or on the trigger would be good - basically a 'turbo' button. I don't find the location of the brake button ideal for full throttle.

 

Out of interest - of 4 throttles I have, I get 3F (yippee!), 38,37, and 36. I haven't got a decent calibrated meter up here, but using the one I have got, I get these values, shown against their hex equivalents:
36=4.17K, 37=4.26K, 38=4.37K, 3F=5.64K

Scalextric are aware of the problem, and their reply is:
"Throttles: There are productions variances and you may have two controllers which are at opposite ends of the variances."
Hmm. Thanks Hornby!

I also tried getting the hex values for each controller in a different socket, to see if there is much difference in the AD conversion, but it appears that there isn't! The hex values remained the same for each throttle, regardless of hole it's plugged in to.

 

An interesting range of values, showing that they probably are 10% resistors. Nice to see one at +10%

Had not realised that Scalextric were aware of the problem. I wonder when the spotted it? Presumably after the release of the V1.3 Powerbase, or they would have fixed it in that.

Silly thing is to blame the problem on the throttle. In the Analog world mabe. But in the digital world it could have been dialed out with a one Byte change to the firmware.

I like you found the Powerbase to be very consistent between inputs. So all of the variance down to the throttle.

 

Hello Richard,

just a quick question: Did you actually meassure the max. PWM with different hand controllers?

Otherwise there would be still a small possibility that the manufacturer does not use all available 64 speed steps. For example if the tolerance of the controller resisitor is max. 10% then just set PWM to 100% from codes 64 - 10% up to 64 = 58..64 (all values are decimal).

Regards

Juergen

 

Hi Jeurgen

I measured the PWM on a car motor control board. That is where my 4/5 on to 1/5 off for a 35 Hex controller came from.

I also checked that Hex 3F gave a fully on motor, which it does.

I agree with your assessment of what the manufacturer should have done.

Richard

 

Hi Richard,

Thank you very much for the detailed explanation. Sorry to say but I also do not know an easy solution for this problem.

One possibility: add another poti with i. e. 1kOhm in serial with the original one. When you release the trigger the sum of both resistors will be 0 + 0 = 0 Ohm. When the trigger is fully pushed the sum will be i.e. 1k + 4k = 5kOhm. But it might be difficult to install a second poti.

Regards

Juergen

 

Your solution would work but physically I do not think it is possible.

I see four solutions.

1) Ignore it and concentrate on the racing.

2) Measure the controllers, mark them up and make sure that as well as choosing the best car you choose the best controller.

3) As above but pair the best controller with the worst car.

4) Not for the faint hearted this one. Open up the powerbase, the controller circuit is a potential divider 1.8K to 5V and the the controller 5K to ground. If we reduce the value of the 1.8K this has the same effect as increasing the 5K.

A bit of maths shows that if the 1.8K was reduced to 1.6K this would have the desired effect. Alternatively if you soldered a 15K resistor in parallel with the 1.8K this has the same effect, and saves removing the 1.8K

However as I said this is only if you know what you are doing. These are small surface mount resistors and you have got 6 to do. So I recommend 1,2, or 3.

 

Would a 2k variable resistor mounted above each controller socket work better?
(Replacing the 1.8k resistor)
Then you could manually adjust the maximum throttle for each car, evening them all out and slowing down ones for kids etc.

Kambuk

 

The problem is that from the controller socket you only have access to the input to the A/D and Gnd. Putting a variable resistor in series with this will enable you to increase Max Throttle, but as I said in the original post, you also increase Min Throttle. Cars begin to move at 0.3K so you don't get much scope.

Reducing Max Throttle for kids is best achieved by opening the controller and either physically reducing travel or by fitting a pot across the 5K resistor.

You post has however promoted a messy thought. The 1.8K resistor is connected between 5V & the Controller input. We have access to the controller input & we have access to 5V on the Aux port.

So some messy wiring would allow connection of the 15K across the 1.8K

I have to say that I don't like this solution it would need 6 plugs and sockets and a lot of wires.

Also a word of cauction. The 5V regulator output in the Powerbase has a surface mount 0.5 Amp fuse. Messing about with anything on the Aux Port can easily blow it. Of course I have never done this.

If your Powerbase has ever shown the symptom of backlight on but no display, this is probably what is wrong.

Richard

 

I was meaning remove the surface mount 1.8k resistor, drill some holes in the top of the unit for the top of the variable resistor to poke through and solder wires from the variable resistor to where the surface mount resistors were (tricky but doable with the right tools).

Kambuk.

 

If you are willing to drill holes etc,

then you can do most things.
Had been trying to keep the Powerbase intact and modify externally.

 

This topic has been idle for awhile so I don't know if this will reach anyone but i wanted to add a few neophyte comments. First wanted to thank Rich and everyone else for all of the great in depth topics. Great reading.
Second, even though I feel like an minority on this forum because I have SCX digital and not SSD, I was glad to read that throttles can have varying degrees of power. It was driving me crazy but i have 1 throttle (out of 7) that outputs so much more power then the others. I think for now I will just have to match it to the slowest car.
Third, SCX Digi does have the jr speed option built right into the control unit. It works amazigly well. Rich maybe you could borrow that idea for the ssd system and solve one of your issues, IMHO.
Though I imagine there might be some legal issues with that

Ps,
I'd love to see that poll again on who owned which set and from where. Might be cool to split it up between digital and analogue.

 

Hi, Thanks for the nice comments, glad someone appreciates the research.

I do not know the SCX system but am intrigued as to how one controller produces MORE

power than the others.

This implies that all SCX controllers are deliberately restricted

I sugest that someone that owns one takes it apart and make a few measurements. This should quickly reveal what the differences are and also the Jr speed mechanism.

Assuming that the SCX controllers have a variable resistor and that these feed A/D converters in the control unit (like SSD) then they have two choices for Jr speed control.

1) A simple additional resistor that is switched into circuit to restrict maximum power.

As an aside this requires the control works in conventional fashion, i.e. Max resistance is Min speed and Min resistance Max speed.

2) That it has an additional signal line which selects a different throttle map in the Control unit.

This would be nice but suspect unlikely

Perhaps someone has already analysed the SCX system, has anyone got a link

 

Hi Rich,
I haven't seen much written on the scx system compared to SSD or Carrera. Seems all the enginneers/programmers are SSD guys...