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Vendor
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More or less the voltage drop is the same regardless of the voltage, so a 0.5V loss at 12V is greater, in % points, than 0.5v at 14.4, but not by much
The power also varies with the square of the voltage, so from 12v to 11.5 the power drop is around 8.1%, 14.4 to 13.9 around 6.8%. Hardly noticeable.
However, a higher voltage is not always the best when it comes to lap times, as it may make the car more difficult to control and possibly with more wheelspin.
 

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Discussion Starter · #62 ·
I lost the track of where this is going: are you talking about using the SCP1 as an analog controller with the analog cart and checking the drop in voltage introduced by the controller?
Yes, I'm using my SCP1 as an analog controller, with a low current analog cartridge. I know that full throttle power goes through an electronic device, not metal contacts, so there HAS to be a voltage drop. How much? I didn't know. Mauricio mentioned it somewhere in this discussion. I'm not really concerned with the actual voltage drop. I'm concerned over the actual on-track difference it might make. My experience shows that it makes less difference at 14.4V than it does at 12V. I really like the SCP controller. I'm seriously considering getting a high current cartridge, and adding a blast relay.
 

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ParrotGod
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I have a friend of mine that races in both analog (wood track with no magnets - the real thing) and digital.
On the analog track he races with an SCP1 and he is one of the top finishers.
All the others have MB and other more typical analog controllers. So I do not think that it makes much a difference.
I think that he has the high current cart.
 

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Discussion Starter · #64 · (Edited)
Recently at work, I discovered that we have an electronic load. Cool, I thought! That would make testing my controllers a trivial matter. Here are the results. I think the column headings are self explanatory, but I'll explain them anyway.

I, A is current in Amps.
Vdrop, V is voltage drop in volts.
Ploss, W is power loss in Watts.
Ploss, % is power loss in %.
SCP LC is my SCP1 controller with low current cartridge
Analog is my analog controller that uses metal contacts for full throttle.

I measured the voltage drop from the black alligator clip to the white alligator clip at various current levels.

275467


I was very surprised at how much voltage drop the SCP controller generated. Then I tested the analog controller, and was also surprised at how much drop it had. It's better than the SCP, but not as good as I'd expected. Slot car controllers apparently just have more voltage drop than I expected.. I can see why people use blast relays for high current motors.

My question is, how much current do our motors draw? The hottest thing I'll likely use would be a NSR 25K KING EVO 3 MOTOR, LONG-CAN with 350gcm of torque. How much current would such a motor, in a car with traction magnets, draw when exiting a corner? I don't really care about draw at startup. I'm more interested in current draw under race conditions. I suspect that 1.0 A is on the high end for such a motor during a race. At 1.0 A, the SCP drops an extra 0.129 V. Not bad.
 

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Alan Wilkinson
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Recently at work, I discovered that we have an electronic load. Cool, I thought! That would make testing my controllers a trivial matter. Here are the results. I think the column headings are self explanatory, but I'll explain them anyway.
Nice to see the numbers.
Thanks for this.
I'm still undecided whether the power drop really matters in race conditions.

For high power motors, like the king 25 or 30, the challenge is setting the car up to contain that power and preparing the tyres to put the power down to the track. With these motors, I often use the traction control to soften the attack so having a bypass relay kicking in will only make the challenges worse.

For low power motors, In classes where everyone is using the same motor, this power loss might create a disadvantage to the SCP user.
However, with the smaller motors (eg slot.IT's SIMX16) , the power loss is very small because the current draw is low.

Then, there is the politics of club racing.
I'm an advocate of electronic controllers because the provide reliability and tuneability.
Those 2 factors alone outweigh any small power loss that occurs.

I use the scp2 METAL cartridge and I do not know if the power loss is reduced compared to the regular cartridge.

I would not be comfortable turning up to a club night with a Frankenstien controller. (An scp2 metal with bypass relay)
That kind of lash up would be a disincentive for other slotters who do not have the skills to replicate that set up.
I would also be concerned that I would compromise the reliability of the scp by the addition of wiring and relays.
I could probably hide the modification inside a wiring sheath and inside the controller's plug but for me, that would be cheating. i define cheating as "doing something that you want to keep secret and that would cause embarrassment if you were ever caught doing it)

However, im surprised that Slot.IT designed a unit whee there is a power drop built in to the design.
I have seen RC MOSFET speed controllers where multiple mosfets are used in parallel to reduce the power loss and I assumed (incorrecty) that this is how the scp was designed.

Alan Wilkinson
 

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Greg Gaub
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14,648 Posts
I have a relay and the metal cartridge, and have not installed it for all the reasons you mention.
I'm sure slot.it understood that there would be a small loss of power, but for all the reasons you mention, it's not of much concern for the cars it's made for. The metal cartridge should have measurably better power, but I expect there will still be some loss, which is why they designed it to work with a relay if the user wanted to add one. Again, much less of a concern for most of the kinds of cars we drive. I've been quite happy with my SCP using a metal cartridge. I currently (LOL) have no plans to add that relay.
 

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Discussion Starter · #67 ·
Nice to see the numbers.
Thanks for this.
You're welcome.

For high power motors, like the king 25 or 30, the challenge is setting the car up to contain that power and preparing the tyres to put the power down to the track. With these motors, I often use the traction control to soften the attack so having a bypass relay kicking in will only make the challenges worse.
If you have some Power Trim dialed in, I don't think the relay kicks in immediately. I think the power ramps up as it does without the relay, and when it gets to the "full power" point, the relay kicks in.

I would not be comfortable turning up to a club night with a Frankenstien controller. (An scp2 metal with bypass relay)
That kind of lash up would be a disincentive for other slotters who do not have the skills to replicate that set up.
This wouldn't bother me at all. At all of the local clubs (HO and 1/32), people are using controllers that are no longer in production. Maybe it's one that where a local guy built 5 of them, and sold the extras to buddies. Or a boutique mfr who's retired. And in RC racing, it's not uncommon for a racer to modify an ESC with additional FETs. So in slot car and RC racing, it's not uncommon for people to be using something that's not available to the public. And really... cars are the same way. A car that's been well tuned for a particular track is not available to the public. You could argue that adding a relay to a controller is equitable to tuning a chassis.

I would also be concerned that I would compromise the reliability of the scp by the addition of wiring and relays.
This could be a concern, as you are adding a moving part to an assembly that previously had very few.

However, im surprised that Slot.IT designed a unit where there is a power drop built in to the design.
I have seen RC MOSFET speed controllers where multiple mosfets are used in parallel to reduce the power loss and I assumed (incorrecty) that this is how the scp was designed.
How old is the SCP design? The ultra-low resistance MOSFETs were likely not available then. Paralleling a few wouldn't have been a bad idea, though.
 

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novice jazz player &
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6,106 Posts
Is the point here perhaps that an electronic throttle controller will likely have a diode to prevent risk of damage if accidentally wired back-to-front?

What is more surprising to me is that a pure analog controller also has a non-linear voltage drop. I wonder why?

c
 

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Slot King
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Interesting measurements, thanks, it would be nice to see the results for a high current cartridge.
A 5% drop is significant, and easily avoided in an all electronic controller, re-inforces my opinion that the SPC design is flawed in several ways, it seems as if it was created purely as a technical exercise, on paper it ought to be the best, in practice it is proper marmite.
Dr_C the non linearity is caused by a single measurement (at 1A) otherwise seems ok to me.
The moral of the story is, if you want to go fast, hang on to your old Parma controllers. ;)


Joel
 

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novice jazz player &
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6,106 Posts
Thanks Joel, what was surprising me most was the apparent variation of internal resistance for the analog controller as a function of current. If its just wires and switching contacts why the non-Ohmic behaviour? I guess I need to check out the circuit diagram - I wonder if the diagram is available anywhere on-line?

c
 

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Alan Wilkinson
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..on paper it ought to be the best, in practice it is proper marmite.
Joel
Wholeheartedly agree. I'm not surprised that many genuinely hate this controller.
I use the SCP primarily because I race analogue and oxigen digital.
There is no other controller that can do both so, for me, no choice.
Technically I rate the SCP at 95%
Cosmetically and ergonomically, it is less than 50%

  • horrible for lefties
  • bulky
  • non intuitive
  • ugly.
  • ergonomically challenging (especially in endurance digital racing)

Marmite. . I know where I stand on marmite, I love it.
SCP . I don't hate it, It's good enough, but it really could be improved.
 

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Discussion Starter · #74 ·
Is the point here perhaps that an electronic throttle controller will likely have a diode to prevent risk of damage if accidentally wired back-to-front?

What is more surprising to me is that a pure analog controller also has a non-linear voltage drop. I wonder why?

c
I wondered that, too. At full throttle, there are metal contacts.

I mean... there's no such thing as NO resistance, right? :)
Correct. Not until we get superconducting controllers. :)

Interesting measurements, thanks, it would be nice to see the results for a high current cartridge.
If somebody would like to send me one, I'll be glad to test it.

A 5% drop is significant, and easily avoided in an all electronic controller, re-inforces my opinion that the SPC design is flawed in several ways, it seems as if it was created purely as a technical exercise, on paper it ought to be the best, in practice it is proper marmite.
Dr_C the non linearity is caused by a single measurement (at 1A) otherwise seems ok to me.
The moral of the story is, if you want to go fast, hang on to your old Parma controllers. ;)


Joel
Not sure I agree that a 5% drop is all that problematic. You all DO notice that the analog controller drops 2.7% at the same current level, right. How many of your cars draw 2 A? At a recent race with 25K motors on cars with strong traction magnets, I watched the current draw on the power supply. It occassionally went over 3 A, but not often. I'd guess that the cars were drawing a max of 1 A each. If you're running metal chassis cars on commercial tracks, then yes you may have a problem with this controller. For 1/32 plastic chassis cars, I don't think it's a problem.


Thanks Joel, what was surprising me most was the apparent variation of internal resistance for the analog controller as a function of current. If its just wires and switching contacts why the non-Ohmic behaviour? I guess I need to check out the circuit diagram - I wonder if the diagram is available anywhere on-line?

c
I don't know of an online schematic for this controller, which is a One Stop. An older model with 30 bands. Not the new, wiperless model.

Wholeheartedly agree. I'm not surprised that many genuinely hate this controller.
I use the SCP primarily because I race analogue and oxigen digital.
There is no other controller that can do both so, for me, no choice.
Technically I rate the SCP at 95%
Cosmetically and ergonomically, it is less than 50%

  • horrible for lefties
  • bulky
  • non intuitive
  • ugly.
  • ergonomically challenging (especially in endurance digital racing)
I agree with your technical rating, but I don't really care if it's ugly. As for non-intuitive, any controller with this much functionality is going to be complex. If I had designed it, I probably would have emulated the brake & sensitivity adjuster locations of a DiFalco and One Stop. That seems to be more common. As for ergonomically challenging... not sure I agree. Yes, it COULD be more comfortable, but it's MUCH lighter than analog controllers. For long races (which I've not done with an SCP), I would think the light weight would be very welcome.
 

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Slot King
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5% not much? Let's all pray the taxman doesn't see it that way and put the rates up by a not much 5%.
If you read the post by Slot.it, a .5V drop (at 1.5A) is equal to a power drop of 8.1%.
At 2 A the power drop would be around 11.4%, which is double what you measured with the analogue controller, given the choice I would rather not lose that much.
My technical rating would be no more than 60% with 40% for ergonomics.

Joel
 

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Greg Gaub
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14,648 Posts
And yet, I still got the fastest lap by a couple tenths using mine at last night's race for the King of the Hill (hot lap) challenge for the night, against guys with DiFalcos and DS and other hot ticket controllers.. one of whom was the track owner, Alan Smith, which is not someone I'd normally expect to get a hotter lap than on his home track... ever.. And this weren't no plastic home track. This was a 6 lane wood track, well over 100 feet long, used for many nationwide and worldwide scale endurance races.

Huh... go figure.

(Track showcased in this video, shortly after it was assembled, prior to his new location opening)
 
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