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There is so much more to a
controller than how many bands or whatever whizbang features it has. If the
focus by manufacturers and consumers is only on number of bands or what new
widget it has, progress in other important areas will be neglected. I have
seen this in other areas of endeavors where the numbers-race-madness blinds
people from what is a genuine technological advancement.
When shopping for a controller, consider all the major brands, Ask
questions, Call the manufactures and listen to the reasons for the things
they do. Don't just buy what some hot shoe recommends.
Here are some questions that need to be asked so you can cut through the
clutter:
1. Is the controller overly complex and does its complexity have a real
advantage or just a marketing one?
2. What effects does the complexity have on reliability?
3. Is the potential improvement that complexity adds so slight that it is
not worth doing?
It is important to
understand that controllers operate under a very harsh environment and must
be very rugged electrically to survive.
4. Does the controller have any multi-pin (more than three) I.C. chips?
Most of these devices have
low voltage ratings which can cause problems with the harsh environment in
the track, car and controller circuit. I have had first hand experience with
this when I used a 30 volt rated schottky barrier diode and I started having
failures of this part. I went to a 100 volt rated rectifier diode and the
problem went away. So what's happening? The motor's inductance in the
circuit is generating high voltage spikes and oscillations. I question the
wisdom of using these devices (chips) when a very good controller can be
built without them.
5. Is the mechanical trigger mount to wiper contact design flimsy,
inaccurate and difficult to repeat?
6. Does the controller have one or two power transistors to ensure enough
amperage headroom and reduce voltage drop at full transistor power?
7. Does the controller have individual bands and resistors that allow it to
be re-curved?
8. Does the controller have a fuse on its transistor output thereby saving
an unnecessary repair?
9. Does the controller have the ability to load regulate? (the sensitivity
feels about the same when you change to a different wattage motor).
Controllers without this can sometimes be a pain to get it to feel right and
require more adjusting to get things right.
10. Does the controller have no dead band?
Without a dead band if the
trigger stop contacts are fouled with dirt not only will you lose brakes but
it will also fail to turn off the transistors - making for an even harder
wall blast.
Back to the band number controversy. Yes, I could of put more bands on my
new 18 band board but I was concerned that if the bands became too narrow
that the glue that bonds the copper to the board might fail over the long
term. Also, the gaps between the bands need to be big enough to reduce
problems with conductive dirt bridging the gaps.
It's important to understand that as you increase the number of bands the
voltage increase from band to band gets very small thereby reducing the
chance of upsetting the car. Also, your trigger finger only has so much
precision to it in the first place.
This is where a smooth trigger is very important which makes it easier to
control with your finger. I've had racers ask me if ball bearings really
help and my answer is a definite yes. After building thousands of
controllers with and without ball bearings, the controllers with ball
bearings simply feel better. The trigger returns easier, it has less play in
it, and it's definitely easier for your finger to control the trigger. |
Transistor Controllers
