Dave,
Can you post a circuit diagram for the power transistor method?
200msec pulse worked for me, too.
As I've ended up making these pretty much ad hoc, I don't have a clear
schematic written down. However, there are projects on the web about
how to control a TIP120 from an Arduino. An example is here:
What you need is to set up two circuits like this, one to push the
current in either direction.
I realize this is too much handwaving, however I'm having trouble
posting a file with a rough schematic, so I'm going to try to describe
it verbally.
Essentially the circuit is a variation of how to control a single coil
machine like a Kato, with a circuit for a twin coil machine. Basically
you have three wires in and two out. Power normal, power route and
common in, two wires to the coil out. The normal and route input go to
the coil inputs. There are resistors between the inputs and ground, so
that when you apply a voltage to one of the inputs, some of the current
goes through the coil, back through the opposite resistor, to power the
coil and some goes (wasted) through the adjacent resistor to ground.
Got that?
So for controlling a Kato coil with an Arduino and power transistors
you need your input voltage, ground, the wires to the Kato coil, and
wires from two Arduino output pins.
Voltage connects through the resistor to the TIP's collector, and to on
lead to the Kato coil. This is repeated for the other coil wire.
The TIP emitters are connected to ground.
The pins from the Arduino to the base pins on the TIPs.
For the resistors, I've been using 22 ohm 5 watt units, but this is not
critical, anything from about 20 to 35 ohms, and at least 1 watt should
work.
I hope this is clear.
Bob
