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16  Using Arduino / Motors, Mechanics, and Power / Re: Driving 70v 6.3A Bipolar Stepper on: April 13, 2014, 04:23:45 pm
I don't see how to use it with my motor driver.   I need only a direction and step pin.

Specify it like:

AccelStepper myStepper(AccelStepper::DRIVER, stepPin, dirPin);
17  Using Arduino / Motors, Mechanics, and Power / Re: Deciding which servo fits better on: April 13, 2014, 04:08:55 pm
Here's a 360 degree servo. Metal output gear too.
18  Using Arduino / Motors, Mechanics, and Power / Re: DIspense very accurate micro volumes on: April 13, 2014, 04:06:28 pm
Ho, it looks very nice.

So there is the stepper AND the pump in this stuff right ?

It looks like the tubing was designed to sit on the top of the "pump" with a cover (missing) to hold it down tight; the white pieces apparently move up/down in a wave fashion to squeeze the liquid through the tubing. Never seen one like that before.

So if you can make a cover for it it'd probably work. Hard to go wrong at that price.
19  Using Arduino / Project Guidance / Re: Need Help controlling 4 DC Motors, 5000 RPM, 115 V. 1/15hp on: April 12, 2014, 08:47:04 am
That's a universal motor, the same type of motor that you'd find in an angle grinder, blender, woodworking router, AC corded drill, etc. It can be wired to 115V mains wiring directly for full speed or you can use a "router speed control" for variable speed.
20  Using Arduino / General Electronics / Re: LM317 + PWM needs less voltage at the top end and 0V at the low end on: April 12, 2014, 04:47:48 am
Rather than just asking for 'an answer,' the best I'd like to see is a web page that describes clearly and most importantly simply how to adjust the gain on the 358. The only pages I've found assume the reader has a lot more background than I have.

In the EDN link it's using the Op Amp in an active low pass filter. Putting that another way, the R/C filter alone does not smooth the PWM output well enough to control the LM317 stably. TI's "Op Amps for Everyone" describes active filters in section 16.

Back to the LM317, in a classic arrangement with a resistor (R1) between OUT and ADJ and second (R2) between ADJ and GND, the LM317 works by increasing voltage at the output until the voltage on it's ADJ pin reaches 1.25V. The two resistors act as a voltage divider. So the OUT voltage is increased until it equals R2 / (R1 + R2) * 1.25. When you apply current to the ADJ pin externally, with the active filter mentioned above, it causes the LM317 to adjust its output.
21  Using Arduino / General Electronics / Re: Why won't Eagle route this airwire? on: April 12, 2014, 03:49:27 am
I put two on every board, with vias connecting them.  Vcc traces over the plane adds some capacitance for the power signal. Hard to get any capacitance when Gnd is connected to Gnd tho.

Isn't the capacitance a good thing though? I thought it was better to have one plane VCC and the other GND for the benefit of that extra capacitance.
22  Using Arduino / LEDs and Multiplexing / Re: How to choose an appropriate LED Driver for PWM dimming on: April 12, 2014, 03:30:22 am
Thx Grumpy_Mike. I have confirmed that the transformer is actually just a power supply (converts AC->DC) and does not contain any driver, so If I select an LED Driver that outputs constant current less than or equal to 650mA (the max current my LEDs take) I should be fine right?

That is a LED driver; it states it quite explicitly on the label. It is not a "transformer" and I'll guarantee that if you try to use it as a DC power supply that it won't work.

With regards to controlling it with PWM, either by switching the AC input or the DC output, that won't work with this type of driver either. Try a simple test: turn it on and see how long it takes for the LEDs to light up. It's just a fraction of a second but what you're seeing is the driver attempting to reach a stability in its current output causing the delay.

The driver states a "30 - 46VDC" output voltage but what that means is it's only stable when the Vf of your LED string is between 30 and 46Vf. If you have any 650ma LEDs you can try a simple test by just connecting a few of them (Vf outside of 30 - 46Vf) and what you'll see is the LEDs flickering. Again, the driver is not stable outside of 30 - 46Vf so you can imagine what would happen if you tried to PWM that output. It does not work like a typical DC transformer.
23  Using Arduino / LEDs and Multiplexing / Re: Can I measure current on LED driver? on: April 12, 2014, 02:17:23 am
Just a minor correction: the "50W" version states 1.5A; the "30W" version states .9A.

I think the more appropriate way to describe LED drivers like these is that they just plain output the given amperage (.9A), but they can only regulate that amperage stably when the total forward voltage of the LEDs is between 28 and 40Vf. It is safe to connect LEDs where the total forward voltage is outside of 28 to 40Vf but what you'll see is a lot of flickering of those LEDs.

In other words, describing it as a "30W" driver is inappropriate. It's really a .9A current regulator that is only stable with a LED string between 28 and 40Vf. And as a corollary to that the critical spec is the .9A current -- make sure the LEDs you're using are designed for .9A.
24  Using Arduino / General Electronics / Re: LM317 + PWM needs less voltage at the top end and 0V at the low end on: April 12, 2014, 01:53:28 am
Just to be clear, your end goal is to vary the output voltage of an LM317 digitally? If you're just trying to achieve a single voltage then all you need is a resistor.

I understand that with a 12V input the LM317 has an 'unavailable' voltage drop, but I don't know what the name of the spec is in the data sheet. Regardless, if it's in the 1.5-2V that brings me closer to the target of 9V.

I believe you're referring to the "dropout voltage". The input voltage - dropout voltage specifies the highest voltage that the regulator can regulate. It varies with current passing through it: -- see Figure 4. So for 1A of current the dropout voltage is stated as 2.2V. With an input voltage of 12V the highest output voltage you can configure the regulator for is 12V - 2.2V = 9.8V.
25  Using Arduino / Motors, Mechanics, and Power / Re: need a high pressure solution for blowing up a balloon after opening a container on: April 11, 2014, 11:36:17 am
Depending on the air source you would need a regulator to keep the pressure down to <10 PSI, and then from there any pneumatic solenoid would work.

If you can provide more details on what you're using for an air source, how small/portable your apparatus needs to be, and what side of the planet you're on then you'll get more direct help. Don't be afraid to explain what you're trying to accomplish.
26  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Micro - driving relays for seat warmer on: April 11, 2014, 11:31:03 am
Would you be willing to remove/change the current limiting resistor to the optocoupler so it will work with 5V? The resistor shown in your eBay link (other thread) shows "103" (10K) so just by sticking another 10K resistor on top of it / in parallel you should get enough current to activate the optocoupler at 5V. You could test this non-destructively just by holding the resistor across the SMD resistor's contacts.

Regarding 12V into "RAW", the regulator is still regulating that to 5V so it's not going to solve your problem. What you would need is an external 5V regulator -- one that can handle the current to drive the relays -- and then connect that to the 5V on the micro. With respect to the "you can't do that" part it would work with boards like an Uno but I'm not sure the micro has the same protection.
27  Using Arduino / Sensors / Re: High sensitivity gyro? on: April 11, 2014, 10:52:09 am
A gyro is not the way to go for this. Specific to the L3DG20 is reports a "Digital zero rate level" of 10 degrees/second; that's the inaccuracy of the device when it's just sitting at rest, reporting up to 10 degrees/second of movement. This inaccuracy is typical for any mems gyro.

What you would need to use is a rotary encoder, but you're asking for one with 360,000 counts per revolution. For something with that accuracy I think you'd have to steal one from an observatory with a high power telescope.
28  Using Arduino / Project Guidance / Re: Need Help controlling 4 DC Motors, 5000 RPM, 115 V. 1/15hp on: April 11, 2014, 10:23:00 am
1/15HP is only about 50W. That's a pretty weak motor compared to the typical brushless motors used in RC.

I wouldn't say that brushed, 115V DC motors are uncommon but the motor controls available typically need 120V AC input. Finding a control for a battery application is going to be a problem -- I've never seen one. Also, brushed DC motors of this type are typically biased to spin faster in one direction than the other so if you do need to get that kind of speed balance you're probably looking at the wrong type of motor.
29  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Micro - driving relays for seat warmer on: April 11, 2014, 09:26:31 am
See for help on wiring it using the optical isolation. With that scheme you're powering the relays with the car's 12V and it only needs ~2ma from the Arduino, per relay.
30  Development / Other Hardware Development / Re: List of tools for surface mount work on: April 10, 2014, 08:50:41 am
I don't like those vacuum pickup pens either. Much easier to use a tweezers.

The really small tips for soldering irons aren't that easy to use. Unless you're working with very small pins like on a TSSOP (smaller than SOIC) you should stick with the "normal" sizes.

Someday I hope to build a custom "hot plate", about 15cm square, for doing reflow. A toaster oven sounds like a good idea if you're using solder paste/stencils but I'd like to have something that I can reflow on and still be able to manipulate the parts by hand.
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