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'[OT]: Helicopter stuff'
2000\09\14@182038 by Sean Breheny

face picon face
I've never had so many threads going on the list at once, so picking a
subject is a bit confusing :-)

Thanks to all those who replied about encoders. We were planning on
upgrading our motors soon, so at this point we are debating whether to go
with the current motors/better encoders, OR switch to brushless motors
(to get beter power/weight ratio and eliminate the need for encoders,
since we only need to control speed, not position). We weren't able to
find (in my short web search) encoders which were light enough yet could
tolerate as much shaft play as we have. I don't think that flexible shaft
couplings are the answer because we have considerable up/down shaft play
(axial play?)

SO, my question is, where can I get a tutorial on driving high power
(100W and greater) brushless motors? Are there existing brushless motor
controllers which are small,light weight, and accept an input signal
which can be correlated to output speed to better than 5% (preferably
direct digital serial or parallel input)?

Thanks,

Sean

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2000\09\15@023516 by staff

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face
Sean Breheny wrote:
{Quote hidden}

Sean, if you just want 5% or better speed accuracy from the
encoders you don't need commercial position encoders. Just make
black disk, attach to the motor shaft and have a hole on the
disk. You can get infra-red transmit/receive opto interrupter pairs
for a few bucks from just about anywhere.

Then use PIC (or whatever you like) to measure the
period between pulses from your home made encoder. You can get
a professional result from this if speed measurement is your
main goal, easily 1% or better speed measurement. Shaft
play will not matter much if you average the speed over a number
of pulses. This will work well and may save you the cost of
expensive new motors when all you need is to regulate the speed
of the motors you have.

Roman

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2000\09\15@042909 by Alan B. Pearce

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>Just make black disk, attach to the motor shaft and
>have a hole on the disk. You can get infra-red
>transmit/receive opto interrupter pairs
>for a few bucks from just about anywhere.

Or use an AOL subscribe CD ???? ;-)))

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2000\09\15@075040 by mike

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face
On Fri, 15 Sep 2000 16:29:17 +1000, you wrote:

>Sean Breheny wrote:
>>
>> I've never had so many threads going on the list at once, so picking a
>> subject is a bit confusing :-)
>>
>> Thanks to all those who replied about encoders. We were planning on
>> upgrading our motors soon, so at this point we are debating whether to go
>> with the current motors/better encoders, OR switch to brushless motors
>> (to get beter power/weight ratio and eliminate the need for encoders,
>> since we only need to control speed, not position). We weren't able to
>> find (in my short web search) encoders which were light enough yet could
>> tolerate as much shaft play as we have. I don't think that flexible shaft
>> couplings are the answer because we have considerable up/down shaft play
>> (axial play?)
>>
>> SO, my question is, where can I get a tutorial on driving high power
>> (100W and greater) brushless motors? Are there existing brushless motor
>> controllers which are small,light weight, and accept an input signal
>> which can be correlated to output speed to better than 5% (preferably
>> direct digital serial or parallel input)?
SGS-Thomson do a number of BLDC motor control products, and also have
an ST7 micro with a motor-control peripheral on-board
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2000\09\15@084825 by Andrew Kunz

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www.ti.com

They have app notes for making brushless controllers with their processors.
Includes a lot of theory too.

I have downloaded them and put them on a CD for my own use.

Andy










Sean Breheny <spam_OUTshb7TakeThisOuTspamCORNELL.EDU> on 09/14/2000 06:19:21 PM

Please respond to pic microcontroller discussion list <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>








To:      PICLISTspamKILLspamMITVMA.MIT.EDU

cc:      (bcc: Andrew Kunz/TDI_NOTES)



Subject: [OT]: Helicopter stuff








I've never had so many threads going on the list at once, so picking a
subject is a bit confusing :-)

Thanks to all those who replied about encoders. We were planning on
upgrading our motors soon, so at this point we are debating whether to go
with the current motors/better encoders, OR switch to brushless motors
(to get beter power/weight ratio and eliminate the need for encoders,
since we only need to control speed, not position). We weren't able to
find (in my short web search) encoders which were light enough yet could
tolerate as much shaft play as we have. I don't think that flexible shaft
couplings are the answer because we have considerable up/down shaft play
(axial play?)

SO, my question is, where can I get a tutorial on driving high power
(100W and greater) brushless motors? Are there existing brushless motor
controllers which are small,light weight, and accept an input signal
which can be correlated to output speed to better than 5% (preferably
direct digital serial or parallel input)?

Thanks,

Sean

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