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16  Using Arduino / Motors, Mechanics, and Power / Re: Question, do i need encoder for my project? on: July 07, 2012, 05:18:50 pm
If the load is dynamic and you want to maintain constant velocity then an encoder is highly recommended...
17  Using Arduino / Motors, Mechanics, and Power / Re: help with encoder not working on high speed on: July 06, 2012, 03:10:28 pm
Did someone say assembly?
18  Using Arduino / Motors, Mechanics, and Power / Re: Servo + IR remote. on: June 20, 2012, 06:17:10 am
Yes, use a low side current sense resisitor, amplify with an op amp and read with the ADC...
19  Using Arduino / Motors, Mechanics, and Power / Re: Controlling 4 brushless dc motors? on: June 19, 2012, 09:51:45 pm
That's a big servo motor, 9.3 amps at 48 volts and 400 watts...

Not an easy task to run PID, an encoder read, as well as brushless commutation in real time on an Arduino...
As well, the PCB layout and motor driver will be critical at these power levels...

I've dabbled in brush motor servo drives which are tricky enough, I wouldn't even attempt brushless PID on an Arduino...
Starting from scratch without experience, I suspect your looking at least 6 months of learning and work...
I'd recommend an off the shelf driver for them, this one may work and is reasonably priced:
20  Using Arduino / Motors, Mechanics, and Power / Re: TB6560 on: June 19, 2012, 09:14:56 pm
No experience with this specific chip but the interface is CNC standard opto-isolated step and direction.
One pin for direction and one pin for step, send a pulse on step and it moves in the direction defined by the polarity of the direction pin.
It has microstepping as well, which will require that you multiply by this number of steps...

21  Using Arduino / Motors, Mechanics, and Power / Re: Controlling 4 brushless dc motors? on: June 19, 2012, 09:06:38 pm
You can operate the 48v motors on 36v if the current is available, they will just run slower and cooler...
The Adafruit motor shield is for brush motors not brushless...

I strongly advise you to consider brushed which are a lot simpler to drive.
Driving a brushless requires commutation which in turn requires knowledge of the motor position, either through back EMF or Hall sensors...

As well, what level of control are you aiming for?
Position, constant velocity, constant torque?
22  Using Arduino / General Electronics / Re: Ultrasonic Atomizers on: June 11, 2012, 08:49:19 pm
You can generate much faster frequencies with pwm but you end up losing resolution by decreasing the bits/top value...

Normally the atomizer transducers use a self resonant circuit to maximize power transfer.
A Google image search for "ultrasonic atomizing circuit" gives lots of examples like this one:

A few years back I experimented with a 200w ultrasonic traducer, I used phase angle to track the resonant frequency:
23  Using Arduino / Project Guidance / Re: Power saving in code for extended battery life. on: May 17, 2012, 11:00:03 pm
@ gr0p3r

Thanks! I made the project that aleph8nought mentioned.
My light also fades from color to color, I had to up the pwm base frequency after dropping the clock to 1MHz.
The code is linked in the blog post for specifics...
24  Using Arduino / General Electronics / Re: IR Receiver, No Decode on: May 13, 2012, 08:46:19 pm
Or the tsop58038 which is the replacement for the tsop4038...
I have used both for bootloading and lacking AGC they don't turn off with extended duty cycle..

IR bootloader:

25  Development / Other Software Development / Re: Bootloader using photocell? on: May 07, 2012, 05:59:44 pm
Nice job


It was quite a bit of work getting everything to play nice together, especially the half duplex timings and the phase delay...
Looks like it just made Hackaday:
26  Development / Other Software Development / Re: Bootloader using photocell? on: May 06, 2012, 11:07:34 pm
I've just finished up the post for the IR bootloader.
The maximum reliable speed obtained is around 4000 baud, not fast but not terrible...

The info, source and video is here:
27  Using Arduino / General Electronics / Re: Pinout of 328 chip on: May 03, 2012, 06:23:26 pm
Is the entire schematic available also?

Yes, I just added to the blog post:
28  Using Arduino / General Electronics / Re: Pinout of 328 chip on: May 01, 2012, 10:46:50 pm
I've posted my eagle library here, which has a physical layout corresponding to the chip.
It might be useful:
29  Using Arduino / General Electronics / Re: Sharing a thermister on: April 29, 2012, 09:14:22 am
So, do I get the TL072 input from the + of the thermistor (i.e. the field side of the thermistor), or from the MCU side which will be after the resistor (i.e. the midpoint)?

You want to measure at the midpoint as that is the output of the divider.
If you measure without the divider, you will be measuring the supply voltage on the other side of the thermistor, not what you want...

Take a look at the picture at the top of this post:
This is for measuring battery voltage, but in your case R1 or R2 will be a thermistor and the voltage will vary with temperature. 
The post explains the need for the capacitor and the math to calculate the output voltage as well... 
30  Using Arduino / General Electronics / Re: Sharing a thermister on: April 28, 2012, 11:47:34 pm
Does having a thermistor on all the time use a lot of current?

Depends on the resistance of the thermistor and the voltage passing thru it.
You will have the thermistor in a voltage divider:
So add the resistances in series and calculate power with P = V*V/R.

You should be able to share the thermistor but I'd use a cap to ground from the thermistor/divider output to reduce input impedance.
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