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PICList Thread
'[ROBOTS] robot lawnmowers'
1999\04\12@120115 by Lawrence Lile

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Well I started my chassis last weekend, I'm assembling motors and other
stuff.

I'm looking at National's LMD18200 motor driver IC - looks simple to use and
foolproof (an important feature! ;)  )

The PIC's tasks will be pretty straightforward.  I've got a program mapped
out in my head already.

I'm thinking of putting the mower blades both under PIC control and a manual
switch.  That way I can turn off the mower if I'm letting the thing bounce
around in a demonstration for onlookers.

I suppose the PIC could handle input from a tipover sensor.  How abaout
battery management though?

I guess I'm looking for a chip or chips that can handle:

1. Charging a NiCad from a solar cell   (There's another Post on this
today - I'll look for it)

2. Telling the PIC that the battery is low and needs charging. The PIC then
stops mowing and moving, and waits for more juice to arrive via the sun.

3. Preventing overvoltage from teh solar cell from damaging the NiCad

1999\04\12@132719 by Adam Bryant

picon face
Using the reasoning that a component in hand is better than one I have to
purchase, I have been thinking about using parts scavenged from old 5
1/4" disk drives for a robotic lawn mower.  I have several feasibility
type questions that I am sure some of you geniuses on the list should be
able to answer.  For simplicity my mowbot will be plugged in to a normal
battery charger at night and won't have a solar cell or additional
circuitry to manage a solar cell and charging.  I was thinking of using
the stepper motors for drive wheels and the spindle motor for the cutting
blade.  My questions are:

- I have a 6 volt motorcycle battery on hand.  I know the stepper and
spindle motors originally ran on 12 volts.  Will they run at all on the 6
volt battery? Or will I need to add another motorcycle battery or go to a
smallish car battery.  Or is there another option for using the 6v
battery?

- How should I drive the motors from the PIC?  I had thought of just
using MOSFET transistors from Radio Shack (again low cost and locally
available).  The cutting motor will be on/off (with probably an external
on/off switch as suggested below), and the stepper motors will be
controlled by the PIC directly (rather than using a dedicated stepper
control IC).

- Any opinions on whether the stepper motors can handle moving around a
5-10 pound platform?

- Will the spindle motor have enough torque to handle cutting grass?

- Are the components from a disk drive light duty (meaning will they not
last long being used in an environment like this?).

Thanks for the input.

Adam Bryant (age 0x23)
spam_OUTabryantTakeThisOuTspampeaktech.com (work)
.....adamdbKILLspamspam@spam@juno.com (home)
Parker, CO, USA
Robotics, RC Airplanes, anything using a PIC

On Mon, 12 Apr 1999 10:57:16 -0500 Lawrence Lile <lilelspamKILLspamtoastmaster.com>
writes:
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1999\04\12@162126 by w. v. ooijen / f. hanneman

picon face
> - How should I drive the motors from the PIC?  I had thought of just
> using MOSFET transistors from Radio Shack (again low cost and locally
> available).  The cutting motor will be on/off (with probably an external
> on/off switch as suggested below), and the stepper motors will be
> controlled by the PIC directly (rather than using a dedicated stepper
> control IC).

For the stepper you should consider an ULN2803: easier and possibly cheaper
than 8 transistor + diodes etc.
BUT

> - Any opinions on whether the stepper motors can handle moving around a
> 5-10 pound platform?

I don't think so, unless you include a gearbox (which you won't find in a
FDD).
My dual-FDD-stepper robots have just enough power to move themselves
around,
over a smooth surface!

suc6,

Wouter.

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