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Old Dec 04, 2003, 06:24 PM
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Here is the scale PCB.
If you have trouble printing to scale I have a pdf with the above schematics as well in it and it prints out to scale from acrobat.
This image will print out to scale as well with Photoshop or MS paint but not the default windows picture viewer.
PCB should be 18mm x 18mm

Graham, Gail, Ron anyone else do you guys know how to
get the numbers to plug into the capacitor calculation equations?

I will get to work on a controller that uses a PIC and mosfets later. This is for playing around with the motors while they are being developed.


Billy
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Old Dec 04, 2003, 06:25 PM
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oops

Billy
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Old Dec 04, 2003, 07:38 PM
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Hey
I just wanted you guys to know I have not built and tested a circuit from the schematics yet but will soon. I am guessing that it should work
do drive a small motor if we can figure out the capacitor values.
I would guess that the values given in the example might even run a motor just not too efficiently.

Jeff

Would there be much energy loss if the outputs only drove mosfets?



Here are some weight breakdowns
Only parts I weighed are 5145,PCB,and cap
others are estimates.

TDA5145T - 715mg
TDA5144AT - 510mg
18mmx18mmx.4mm PCB - 280mg
18mmx22mmx.4mmPCB - 342mg
10uF electrolytic cap - 110mg

sum for TDA5144AT - 900mg
sum for TDA5145 - 1.17g

so it should be possible to make
a controller using these parts under 1.5g
this would be good if the 6mm brushless performed somewhere between a 6mm pager and an M-20

And for the M-20 based brushless performed close to an N-20.

I guess the Phoenix controller would do for the N-20 based brushless.

Well I'm going to go carve some more propellors.

Billy
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Old Dec 04, 2003, 08:22 PM
"Simplify, then add lightness"
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Billy,
I didn't notice that it didn't have separate emf sense inputs. It doesn't look like you could add Mosfets easily to it. The capacitor values for startup would have to be tuned to the motor you are using. That would be another problem with using this chip. They say to use a value of 220nF if the damping is high, but I doubt there is much if any damping for these little motors, so you would need to know the torque constant, pole-pairs, and inertia for the motor you were running and if you changed motors you would have to change the capacitor. Probably not very practical for a general purpose controller.

Another thing you need to watch for is the maximum power disipation of 1.38watts. If you run VMOT and VP from the same voltage, then you could only pull a current of around 0.7 amps before you exceeded the power rating. Another reason for running a voltage booster for the VP pin.

Jeff
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Old Dec 04, 2003, 08:27 PM
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I think they are running the motors at a half amp.
Will post more later sorry to be so breif gotta run

Billy
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Old Dec 06, 2003, 11:16 PM
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Billy,
have you had a look at micro chips an857pdf doc , has some good info there
Stewart
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Old Dec 07, 2003, 12:52 AM
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Stewart I had looked at the microchip brushless controller example. I will probably try and build one one of these days.
The easiest one to build to get something going quick looks like the TDA5144 chip. I found one in a maxtor hard drive model no
71336a. Probably these things can be had for really cheap by the dozen. I would say folks throw them away.


Jeff maybe stdying the 5142 might help in figuring out how to connect up some fets. I have not realy thought much about how the fet would effect back emf maybe their is a kind of fet that allows current to flow back through it or something. I have not studied how the sensorless controller works enough to know how to deal with it. There is some kind of transconductance amplifier on board the 5144 maybe that is what its for.

Billy
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Old Dec 07, 2003, 01:05 AM
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Billy,
Maybe a fet h-bridge switched by the smd hall sensors would be a simple and lightweight solution ie modify koichi's speed controler by adding the hall switching and fets ,
What do think ?
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Old Dec 07, 2003, 01:33 AM
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billy,
heres 1 of 3 needed ie 1 of these for each winding set then just drive it with a normal speed controler .
Stewart
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Old Dec 07, 2003, 04:37 AM
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Could it be that simple?
Seems like it would work to me.
Wonder about starting it up smoothly?
What's the deal with that?
How could you add the hall sensors to a motor like Mike Cross has built with the flux rings so close?

Couldnt something like this be done for a sensorless motor as well?

Billy
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Old Dec 07, 2003, 04:53 AM
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Billy,
the circuit works , there just is no auto advance to the timeing as can be programed into a microprossor controller . i saw a homemade brushless motor in rc micro flight that had only 2 sets of coils it used this circuit an worked fine .
with the hall switches set to give best performance you may sometimes need to flick start it , small price for easy ?
probly be a bit hard to mount hall sensors to mikes motor but for cd motors it be easy most of them have hall sensors that could probly be reused ?
Stewart
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Old Dec 07, 2003, 04:56 AM
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Billy,
A sensorless controller needs a micro processor to read the emf in the off coil to calculate when to fire the next coil
Stewart
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Old Dec 07, 2003, 07:30 AM
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Billy here is a setup for a 2 phase brushless driven from a brushed controler
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Old Dec 07, 2003, 07:53 AM
It's a spiderweb of knit lines
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Guys
Hall sensors could be added to my 6mm motor by just putting them at the end of the flux ring. There should be enough flux "leaking" out the end of the magnet to trigger the Hall. I'll try it today. You will need to have them adjustable so you can time it, but then it could be glued in place.
Mike
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Old Dec 07, 2003, 08:15 AM
It's a spiderweb of knit lines
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Billy
How do you get chips like that off of a board. I've never been able to remove them without ruining them.
Mike
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