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<a
href="http://datasheet.octopart.com/MTD6501G-HC1-Microchip-datasheet-11052439.pdf">http://datasheet.octopart.com/MTD6501G-HC1-Microchip-datasheet-11052439.pdf</a><br>
<br>
I found it reading<a
href="http://www.elektor-labs.com/project/high-end-propeller-clock-120732.12550.html">
this</a>. After reading wads and wads (but interesting wads) of
stuff about this POV design I got to this:<br>
<br>
"
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<span style="color: rgb(46, 46, 46); font-family: Verdana, Geneva,
sans-serif; font-size: 12px; font-style: normal; font-variant:
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float: none;">I've assembled the propeller on the motor's hub for
the first time, but it's a disappointing experience. With no load,
motor runs very smoothly without any noise, but with the
propeller, it does not manage to start. Sensorless brushless
motors have a particuliar startup procedure which fails with the
MTD6501. I guess the "locked rotor protection" activates because
of the high inertia moment of the rotating assembly. I tried to
fool the controller by adding a few ohms on motor's wires but it
doesn't solve the problem."</span><br>
<br>
But this guy's drive motor runs at five volts and may likely be from
a 2.5 inch drive. I can confirm that hitting a 3.5" drive motor with
12 volts will swing a one pound mass, so the technical hazard with
this chip with a 12v motor is the same as with the TI and Philips
chip: false triggering of the "something is blocking the fan blade"
detection because of the low acceleration going along with high
mass. <br>
<br>
This is the kind of thing you'd put between a simple RC controller's
PWM output and the disk drive spindle motor. Notice you don't need a
controller to run the motor at "full speed" with this chip, as this
can be done by tying the PWM input high.<br>
<br>
One might ask himself/herself whether the .8 ampere limit of this
chip is adequate. Looking at a 2001 Fujitsu blurb about their super
high performance 15k rpm SCSI 3.5" drive and it's total power
consumption of 11 watts, I think the answer for a drive made in the
past half dozen years is yes (and "heck yes" for a 2.5 inch, five
volt drive). The largest version of this chip is an eight pin SOIC
($1.09 at quantity 10 from Digikey) but it would be trivial to
solder dead bug style and set up with a little piece of aluminum bar
stock or something stuck to the thermal pad for prototyping. Hmm,
another idea would be to bend the pins down slightly, solder a long
but narrow strip of copper or brass foil to the thermal pad, then
solder the SOIC chip to a regular <a
href="http://www.adafruit.com/products/1212">breakout board</a>.
It might be that this chip stays relatively cool: my situation
involves worst case currents and duty cycles.<br>
<br>
Also, to clarify, the Arduino servo library would just be to arrange
an appropriate PWM signal to a circuit like the chip above. That's
overkill for this chip. The PWM you get out of the analogWrite
command for supported pins would work (but not for the TI without
using setPwmFrequency: it's minimum PWM frequency is 15khz. That's
hugely faster than what comes out of analogWrite by default). No
way, no how can the disk drive spindle motor be made to move back
and forth and hold a position like a typical servo motor you see in
a model airplane (well, actually it can, but not with the servo
library and a driver chip anything like the ones discussed, and for
only six positions). <br>
<br>
-Pete<br>
<br>
PS Are these reams of verbiage hitting your mailbox annoying you? If
you have a smartphone this might constitute Guantanamo-style
torture. If you follow the link below to the email listinfo you can
go into your subscription settings and turn on digest mode to get
all the mail for the list just once a day. If that isn't good enough
but you want to read this stuff at the time of your choosing just
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1st)<br>
<br>
<br>
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