"Ignoramus32423" wrote in
message ...
On 2015-04-06, Lloyd E. Sponenburgh lloydspinsidemindspring.com
wrote:
Ignoramus32423 fired this
volley in
:

Lloyd, I used those holes to mount TO-220 voltage regulator chips,
not
for anything structural. worked great!

They won't hold with temperature swings, Ig! Put a nut and
lockwasher on
the backside! Go with me on this... I've done many THOUSANDS of
semiconductors on heatsinks, and had both many successes, and every
sort of
failure you could count -- from taking shortcuts. Shortcuts just
never
work in a temperature-cycling environment.

Hm, this is a good point, I did not think about it.

The story is as follows.

My son and I made a robot for a kids homemade robot competition
called
"robocross". He won his local competitions and we will be going to
the
Illinois state competition.

Since the state competition is so important and there is a chance
for
him to become semi-famous if he wins it, we decided to make another
robot.

Here's a picture of it, more or less completed:

http://www.machinerymoverschicago.com/blog/Robocross/

I will hopefully add more pictures and documentation soon.

Anyway, if you look at the controller, you see that there is a
rechargeable battery attached on the bottom, and a black heatsink
attached to the top.

There is a hole in the plastic box where the heatsink attaches, and
in
that hole, there is three positive voltage regulators. One for 10v
to
drive the lifting arm, and two 5v regulators to drive tracks. The
reason for using different voltages is that 10v is too much for the
tracks, the robot becomes not controllable.

The robot itself is intentionally made to work like a skid steer
loader like Bobcat T300. (I have a S300 myself).

The competition itself allows only 3 minutes driving time.However,
he
will spend hours preparing for the competition, and so, the robot
needs to be heavy duty enough not to fall apart or burn out during
practice.

The regulators are KA7810 3-Terminal 1A 10V Positive Voltage
Regulator, and two 1.5A 5V L7805CV Postive Voltage Regulators.

The good news is that, as they run, even after a while, the heatsink
is only barely warm. I had an undersized heatsink (a small copper
bar
inside) before and it would get very hot. But with this aluminum
heatsink, everything is nice and cool.

i

If you used an LM317 adjustable regulator for the tracks you could
tune the voltage for best performance while retaining control, and
waste less of the battery's energy as heat. You could put a knob on
the voltage adjustment pot so you have a throttle instead of just
on/off control.

-jsw