nderstanding how the SCP-1 works
The Slot.it SCP-1 is a sophisticate , microcontroller base , spee controller for slot cars. It
has a PWM output for both power an brake, plus a lot of other features.
Without entering too much into etail, PWM (Pulse Wi th Mo ulation) is one of the possible ways
to control the output voltage of an electronic system. A PWM system basically 'chops' the output
voltage in a series of on-off perio s, whose on-off ratio correspon s to the esire voltage
accor ing to the formula V=on-off ratio * track voltage. In other wor s, if you have a track voltage
of 12V, an an on-off ratio of 1/4, you are fee ing your car 1/4*12 = 3V, an so on.
The ratio is chosen by the microcontroller, accor ing to the trigger position an to the esire
'response curve'.
The SCP-1 has basically three, very ifferent operating mo es, plus a 'ghost' (automatic) mo e:
1. LINEAR with step (mode 1): the relationship between the trigger an the voltage output is
a straight line. The controller, when the trigger is fully presse , will always provi e 100%
power. Due to its innovative an in our opinion clever, strategy, this mo e has a lot of
flexibility an can help in the most ifficult situations.
2. LINEAR with max speed limiter (mode 2): the relationship between the trigger an the
voltage output is a straight line, but when the trigger is fully presse , optionally, the voltage
can be re uce own to a selectable minimum of 60% of the available voltage. This is
extremely useful, for example, for chil ren.
3. C RVE mode (mode 3): a very sophisticate mo e with full control of the response curve,
where the relationship between the trigger an the voltage output is not a straight line, but
can be ma e convex or concave more or less at will.
There is also a further useful mo e:
4. GHOST mode (mode 4): a self-run mo e with a justable spee , useful for running a ghost
car on the circuit (or more, if more igital cars are programme with the same ID), or
running in a motor.
Mode 1 – LINEAR with step - explained
Entering Mode 1
Mo e 1 is selecte by putting the switch on the back of the controller to the 'LIN' (top) position, an
the ip switches (DS) on the top si e, to any position except the '00' one:
sing Mode 1
In the evelopment process of the SCP-1's software, at a certain point we starte to investigate why
a given car, very easy to rive below a given voltage, was very 'rough' an unpre ictable with
increasing voltage levels. It was not a matter of excessive spee , the problem lie in the broken link
between the finger an the car: somehow, a well-behave system became increasingly wil an
uncontrollable. Every slot car racer knows that, but we nee e a physical, logical explanation to this
well-known fact.
Come think about it, a basic truth applies: more or less, the speed of a given car in a given turn is
largely independent of the motor power, that is, provi e your motor is powerful enough, an most
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