Alt-BEAM Archive
Message #10419
To: beam@sgiblab.sgi.com
From: Dave Hrynkiw dave@solarbotics.com
Date: Fri, 18 Feb 2000 15:58:20 -0700
Subject: [alt-beam] Re: solarbotics pager mtr+fan
At 10:47 AM 2/18/00 , jester96beam@iname.com wrote:
>There was a web page someone mentioned a while ago with little
>"helicopters" which used what looked like 4 or 5 pager motors. I don't
>think they were pager motors, but they sure looked like them. These
>minatures bots didn't yet carry any payload, including a power source -
>just the motors and the frame which held the motors together.
The "Mesicopter". 'tis neat. Have talked to the researcher there about
trying the TPMs, but don't know if they have.
http://www-rpl.stanford.edu/RPL/htmls/mesoscopic/mesicopter/mesicopter.html
>What's the torque of the tiny pager motors compared to the regular ones,
>and what's the weight difference?
The TPMs are actually 1.5v @ about 40mA, spinning at 9,000 rpm with 0.8
gm*cm torque, versus compared to the RPM's 13,500 rpm & 1.0 gm*cm torque.
-Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
10420 Fri, 18 Feb 2000 18:00:32 -0500 [alt-beam] Re: More fun questions beam@sgiblab.sgi.com "Sathe Dilip" It is precisely correct for DC conditions as I mentioned. The impedance
part comes in to play only with AC voltages. For DC it is the coil's
resistance that limits the current flowing through it. (If you looked at
the waveforms, you may see the effects of impedance for the first few
milliseconds or so because the sudden application of voltage is a change
for the coil & till it gets saturated, the inductive impedance does play
a part. Once the core is saturated, it is the coil resistance only).
I can think of couple of reasons why your measurements do not agree with
the equations.
First & most likely is that you measured the open circuit voltage of
your supply. On loading it with the coil, if it drops to 3.28 volts,
the equation is satisfied.
If you measured the loaded voltage, your meter in current range should
have an equivalent series resistance of 1.525 ohms. In this case the
difference of voltage (4.5 - 3.28 = 1.22) is being dropped across your
meter itself.
So let us know which of the two scenarios is correct. To verify the
second hypothesis you will need another voltmeter to check the voltage
drops across the meter & the coil individually. By the way what type of
meter are you using for these measurements?
Dilip
----------------------------------------------
Bruce Robinson wrote:
>
> Sathe Dilip wrote:
> >
> > Using the ohms range of your multimeter, measure the resistance of the
> > solenoid coil. Divide the voltage you want to apply by this value in
> > ohms.
>
> Is that precisely correct? I vaguely recall from my student days that
> there was this messy thing called impedence. It was kind of like a
> current through a coil resists itself. Can't remember exactly. That was
> the point I decided I wasn't going to be an electrical engineer :)
>
> Anyway, by way of experiment, I tested a small coil with my meter:
>
> Voltage: 4.5
> Current: 0.8 amps
> Resistance 4.1 Ohms
>
> So 4.5/4.1 = 1.1 amps calculated, versus 0.8 actual. Enough to affect
> which type of driver circuit I might use.
>
> Comments?
>
> Bruce
--
----------------------------------------------------------------------
The early bird may get the worm, but the second mouse gets the cheese.
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10421 Fri, 18 Feb 2000 18:45:41 EST [alt-beam] Re: FYI: ANN: fire-fighting robot contest at Penn State (3-25) beam@sgiblab.sgi.com CIRCITZ@aol.com Could you throw a little more info our way...thanks!!!
Dan
<< Just tought any BEAMers on the east coast near Philly, PA may be
interested in
the challenge on finding and dealing with something other than light. In this
contest the 'bots can touch the walls.
Hope someone tries and let us know the results.
Good luck >>
10422 Fri, 18 Feb 2000 19:02:28 EST [alt-beam] Motor drivers beam@sgiblab.sgi.com BUDSCOTT@aol.com I'm in the process of making my first walker, i plan on using the almost
complete walker design, with the ALS245 driver. how do i hook power to each
of these, i know i need three volts, i'm gonna to (gulp) use two AA
batteries. how do i connect this between the two circuits, do both hook up to
that power source? thx for any response
10423 Fri, 18 Feb 2000 19:17:34 EST [alt-beam] Walker Idea beam@sgiblab.sgi.com BowfinGar1@aol.com I was woundering Is it possible to hook up
a proximity sensor to the complete walker
or is that to much for the little guy?
Thanks
Mark
10424 Fri, 18 Feb 2000 17:00:47 -0800 [alt-beam] Re: More fun questions beam@sgiblab.sgi.com Bruce Robinson Sathe Dilip wrote:
>
> First & most likely is that you measured the open circuit voltage of
> your supply. On loading it with the coil, if it drops to 3.28 volts,
> the equation is satisfied.
Should have thought of that, considering the current draw.
>
> If you measured the loaded voltage, your meter in current range should
> have an equivalent series resistance of 1.525 ohms. In this case the
> difference of voltage (4.5 - 3.28 = 1.22) is being dropped across your
> meter itself.
>
> So let us know which of the two scenarios is correct.
Now I remember why I became a mechanical engineer.
Both scenarios apply, from the looks of it: supply = 3.5 volts under
load, which leaves only .22 volts not accounted for. This could easily
be due to drop across the meter.
Looks like it's time to replace that battery pack. Just too many chips
and transistors turned into heating elements with that last pack :)
> ... By the way what type of meter are you using for these
> measurements?
Inexpensive analog VOM.
Thanks for the info.
Regards,
Bruce
10425 Fri, 18 Feb 2000 17:01:57 PST [alt-beam] electric hellos are getting close... beam@sgiblab.sgi.com "Timothy Flytch" Take a look at this sight... I have recently read were an electric R/C
helicopter has flown non stop for over one hour!!! and they just keep
getting smaller...
http://www.micro-flight.com/
Timothy...
______________________________________________________
10426 Fri, 18 Feb 2000 20:11:46 -0500 (EST) [alt-beam] Re: solarbotics pager mtr+fan beam@sgiblab.sgi.com jester96beam@iname.com Hey Dave how much torque do each or the pager motors (normal and tiny) produce (with the fans if you know) and how much does each one weigh?
I don't think you would need two fans spinning in opposite directions. What would happen if you had two spinning in the same direction? Would it still spin, or would it move in a line? Or would it spin slower?
Chris
---------------------------------------------------
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10427 Fri, 18 Feb 2000 18:02:13 PST [alt-beam] Re: solarbotics pager mtr+fan beam@sgiblab.sgi.com "Timothy Flytch" I saw this one over a year ago... has not progressed since...
Looks like a pipe dream...
Timothy...
>The "Mesicopter". 'tis neat. Have talked to the researcher there about
>trying the TPMs, but don't know if they have.
>
>http://www-rpl.stanford.edu/RPL/htmls/mesoscopic/mesicopter/mesicopter.html
>
>
>>What's the torque of the tiny pager motors compared to the regular ones,
>>and what's the weight difference?
>
>The TPMs are actually 1.5v @ about 40mA, spinning at 9,000 rpm with 0.8
>gm*cm torque, versus compared to the RPM's 13,500 rpm & 1.0 gm*cm torque.
>
>-Dave
______________________________________________________
10428 Fri, 18 Feb 2000 18:18:11 PST [alt-beam] Re: solarbotics pager mtr+fan beam@sgiblab.sgi.com "Timothy Flytch" The main reason for opposite spin on a two rotor helicopter is blade
interference... if they are spinning the same direction than you can't
overlap them... for fear of blade strike... but other wise it does not
matter...
Timothy...
>
>I don't think you would need two fans spinning in opposite directions.
>What would happen if you had two spinning in the same direction? Would it
>still spin, or would it move in a line? Or would it spin slower?
>
>Chris
______________________________________________________
10429 Fri, 18 Feb 2000 20:42:54 -0700 [alt-beam] Re: solarbotics pager mtr+fan beam@sgiblab.sgi.com Dave Hrynkiw At 06:11 PM 2/18/00 , jester96beam@iname.com wrote:
>I don't think you would need two fans spinning in opposite
>directions. What would happen if you had two spinning in the same
>direction? Would it still spin, or would it move in a line? Or would it
>spin slower?
It would still spin, just not as much because the center of rotation is
shared (guessing here). Opposite fans would be idea.
-Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
10430 Fri, 18 Feb 2000 20:43:50 -0700 [alt-beam] Re: solarbotics pager mtr+fan beam@sgiblab.sgi.com Dave Hrynkiw At 07:18 PM 2/18/00 , Timothy Flytch wrote:
>The main reason for opposite spin on a two rotor helicopter is blade
>interference... if they are spinning the same direction than you can't
>overlap them... for fear of blade strike... but other wise it does not
>matter...
>Timothy...
The 2nd benefit is that the torque (twisting force) cancels out, hence no
need for a tail rotor.
-Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
10431 Fri, 18 Feb 2000 22:51:58 -0500 [alt-beam] Re: Geared motors...again beam@sgiblab.sgi.com David Simmons Paul,
So far my son has used the #650-0671, which I am pretty sure is the Hankscraft Motor,
to make his first light seeking Head. Using a FLEDse and the head circuit at BEAM
ONLINE, with a 0.047F 5.5v Cap. It works great, no drag, and very little slip. He is
working on walker with a pair of them right now, but the testing is not going well. Not
sure if the motor is to weak or if Kyle's design is lacking. In a week or so he might
have it all worked out.
Paul Atkinson wrote:
> Take a look at the following from MECI (www.meci.com):
> #650-0671 $1.99 Gearhead motor 2 D cells (3V) and
> #650-0676 $2.99 Two 30RPM gearhead motor 4 D cells (6V or possibly 3V each?)
>
> They look like Hankscraft motors (used in moving store displays).
> If I'm right, the data sheet is at:
> http://www.hankscraft-motors.com/dc3440.html
>
> Has else anyone used these yet?
>
> Paul
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