The Parallax QuickStart board normally uses the USB cable for power.
While this is handy for developing your programs, it's a bit awkward to haul a
full-blown computer around just to provide Propeller power!
My first thought was that portable power could probably be provided by a USB
But two problems -
. 1) what do you do when there is no wall handy?
. 2) the Propeller chip's reset circuitry expects to see a computer on the other
. end of that USB cable.
( I later found out that a jumper from pin 37 (RES or RESET) to pin 39 (Ground)
would allow the board to run from a dumb USB charger. )
But there is an easy way to run the QS board from a battery pack.
The 40 pin expansion header has two pins just for that - pins 39 and 40 -
the two on the far right end. The top row (closest to the edge) is pin 40, which
is wired up as V-IN, the voltage supplied to the on-board voltage regulator.
We'll wire that pin to the PLUS side of the battery pack.
Pin 39 is ground. That one will be connected to the NEGATIVE side of the battery pack.
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Connecting the battery pack backwards would be a bad thing - a VERY bad thing.
So to help prevent that from happening I recommend a 90 degree pin header to make this connection.
This is a soldering job, and a delicate one. Bumps the soldering skill level up a lot.
Start by snipping off a piece 2 pins long.
Next slide the plastic part of the header strip down as far as it will go.
Grip the pins gently with pliars and press down on the table surface until
the plastic strip moves down.
Soldering requires that the parts be held together steadily without any movement
while the solder is wet. Any wiggling at that time will cause what is know as a
"cold solder joint". That would cause higher resistance and be mechanically
So we use an alligator clip to hold the pin header while soldering.
And an alligator clip mounted on a pin vise provides a third hand that is so often
needed when doing this kind of work!
Carefully tin both the pins and wires.
Slip a short piece of heat-shrink tube over the wires and slide it down
away from the the ends so it won't shrink while soldering.
Now - take a deep breath and DOUBLE CHECK the wires.
Make sure you have Positive and Negative going to the correct pins!
When soldering little things like this the parts must be motionless.
You can't make a good solder joint when the wire is moving.
You'll get a cold joint every times.
Now solder the wires to the pins
Getting the pins too hot will cause the plastic strip to melt, but it is
being held securely in the alligator jaws, we won't worry too much about it and just get 'er done.
With the pins clamped in place, and the wires blocked solidly in place it's quick and easy to stick
wires to pins.
There are two wires in this picture, a red and a black. The connection on the red wire looks nice,
shiny, clean. All the visual indications of a good solder joint.
The one on the left, the black wire, looks like a cold solder joint.
When cool it was touched up again.
The next step takes time to complete, but it really helps make a sturdy reliable connector.
That's a glob of Goop - Shoe Goop is really thick, Plumber's Goop is really thin, the rest are somewhere in between.
Almost any kind of liquid cement will do.
This is Plumber's Goop, just a little dab will do ya.
Just wrap a small glob around the pins/wires and let it dry for a while before sliding the heat-shrink up in place
and shrinking it snug.
Use this technique to make cables for your bread board projects.
Useful way to make patch cables.
The angled connector reduces the possibility of connecting the battery pack backwards
because the wires will always come in from the same side...