LabView Alternative for an Automated System to Drive Steppers and Take Measurements of the DUT.

On a sunny day (Mon, 12 Aug 2013 01:53:09 -0700 (PDT)) it happened Klaus Kragelund wrote in :

y This is precidsley the p[oint, and here we 100% agree.

But Pi was brouyght on the market asa LEARNING device (project?).

That is why I reffered to teh Arduino as pree-cooked food... You can find lots of things that already work for it.

For me every new processor, device, chip, board, is a learning project. But I get instant aversion against Arduino (and some of its users) possibly because of the C++ virus, but also because it is overkill for simple applications, and not practical for more complex ones. I see arduino as pre-cooked solution for some some category of people.

Almost anything arduino can do, I can do with a PIC for 2$.

But I cannot possibly port my PC C code to an arduino, or even develop on it. At this moment I am connected with ssh -Y to a Raspberry and editing and compiling some software to drive some hardware:

Resonances... :-)

Nice turn at 55 seconds :-)

But yes, you need some mechanical damping (or SW ramp programmed to slow the steps)

Cheers

Klaus

On a sunny day (Mon, 12 Aug 2013 05:34:03 -0700 (PDT)) it happened Klaus Kragelund wrote in :

The idea is that (with 180 degrees servos) if you go past due north or south, then rotate and flip the antenna the other way to pick up the signal. That should happen as fast as possible (Houston: we have loss of signal..)

Been testing, a lot of the wiggle seems to come from the nylon gears + shaft in the servos I am using. I got a nice 360 degrees one with double ball bearing and all metal gears from ebay, but not suitable for this (no feedback pot), so maybe I will get some 180 degrees servos with double ball bearing and metal gears.

uth,

the steps)

aft in the servos I am using.

So you are using a servo, but with a gear added to that or with a gear that is built-in?

If its built-in (reads the position on the slow axis), you have little cont rol of the way the servo reaches the position. If it reads the position dir ectly on the motor, then you can add lead-in and lead-out slope reduction, so the ressonances does not get triggered so much.

When you are tracking, you only need very slow movement, I guess?

Cheers

Klaus

That's the point. It was brought to the market as a tool for learning programming, not as a device to replace embedded processors in consumer or industrial equipment, for which it is still far too expensive, and for which it lacks the necessary functionality. The Arduino is also far too expensive to replace embedded processors, but it's purpose was to enable the user to learn how to control external devices.

"The Arduinos strength is I/O control while the Raspberry Pi is more a processing device that has the GPIO pins for I/O."

The upcoming Udoo board combines the processing power of the RPi and the I/O capabilities of the Arduino Due and has 12 bit A/D converters. Not yet available. They raised far more money in crowd funding than they had expected and are not taking any more orders until they can fulfill all the orders from backers (>3000 boards ordered).

On a sunny day (Mon, 12 Aug 2013 06:57:54 -0700) it happened sms wrote in :

As I stated in an other reply Andoid is a terrible mistake. And I have one, Android is crap, and these days many google things seem to turn out crap from google earth to their 8.8.8.8, 8.8.4.4 nameservers, their android tools, now all we need is teh search engine further f*cked up. I use bing maps these days to find something. Competition.

As to 'only GPIO', GPIO is all I need, maybe you should actually read the Broadcom technical doc to find out what IS on tha tGPIO and how to use it to it's full extend.

If you cannot figure out how to connect a simple ADC to GPIO then you cannot design embedded either.

No need to wait for any board, get a piece of veroboard and start soldering. If your boss wants a nice PCB, etch one. If you need a thousand China loves you.

:-)

On a sunny day (Mon, 12 Aug 2013 06:18:04 -0700 (PDT)) it happened Klaus Kragelund wrote in :

In the RC servos is a small DC motor, a gear with a large reduction, and on the shaft that sticks out a potmeter (slightly over 180 degrees rotation possible). There is also a chip that wants an impulse form 1.5 mS wide for servo mid-range, at least about every 20 mS or so (no pulse motor powers down). The pulse width sets the position, smaller pulse is more left, wider pulse is more right. As such, as the control loop is in IN the servo, I have no control over that,

wikipedia has some nice pictures of what is in it:

I was trying to get that control loop to oscillate (mass of the antenna plus counter weight as load), and actually had it oscillating for at least 2 seconds (about 1 second period time). The way you could stop it oscillating is power down (remove pulse) I guess, but no way to KNOW if it is oscillating, apart from monitoring the received signal. It is an interesting thing to get that within usable tolerance. Was very well behaved after I stopped pestering it, (I can do that with terminal program, send false values between the 'predict' generated correct ones, to see how it finds the old position back, fun to play with it :-)

Yes, tracking is reasonably slow, ISS however is across the horizon in a few minutes.

Sadly, the world does not revolve around what you need. There are needs that go beyond your own.

If you're not pleased with the plethora of responses, Google "DAQ" or "data acquisition" -- that search term should cough up a lot of vendors.

And you would think wrong.

First of all, there is no official Raspberry Pi power supply, so "counterfeit" is meaningless. Second, Probably 99.9% of power supplies with a Micro-USB connector come from China. Third, the problem with the Raspberry Pi power stems from a poorly written specification and bad suggestions as to what to use.

The issue is that a Micro-USB was not designed to provide so much power. By the time you add some expansion boards, and power some USB devices, you can need several amps of current.

The Raspberry Pi's power distribution is especially poorly designed. They improved it somewhat in removing polyfuses F1 & F2, though this really didn't fix much since F3 is still 1.1A. If they increased the value of F3 so the Raspberry Pi could power expansion boards, more power hungry USB devices, HDMI to VGA converters, etc., they'd need to change the power and ground planes.

The Adafruit supply is one good solution since it puts out 5.25V at 1.1A. But you're probably better off with _one_ higher current supply that can also power a USB hub, an HDMI to VGA converter if necessary, by adding some extra cables and connectors to the power cord to split up the available power.

Well, you can measure the current to the servo, you should be able to see the oscillations there.

But, I think you have chosen a too cheap and low performance servo. If you had used a better one (with less slack in the gear) or a stepper motor with gear, you could avoid the oscillations all together

Regards

Klaus

There is a 'G' code interpreter for the Arduino, and LinuxCNC is freeware.

Dumbass. The phrase was, "We have loss of TELEMETRY"

There were several people selling the Arduino Due on Ebay.

On a sunny day (Mon, 12 Aug 2013 13:18:56 -0700 (PDT)) it happened Klaus Kragelund wrote in :

Yes that is actually a really good idea, normally it is about 70 mA, when motors work it is hundreds of mA. If you drive it into the mechanical end stop the 7805 regulator will overheat and fold back I think. The 7805 will be close to the motors, feed cable has only ground, +9 V, and RS232 tx, normal electricity cable with ground (European), the PIC circuit in the pole.., the 7805 mounted against the alu.. Actually I still need to add a horizontal counter weight arm, still have some staff left.

And a dome, I need a NSA dome, maybe they can donate one :-) Before the public teares those down...

Yes, been looking, those servos with dual ball bearing and metal gear are only about 7$ on ebay. The ones I am using have been in gravity assisted crashes, that is why the tape around those, to keep the parts together, housing is in pieces. There are bad reviews of the 7$ ebay servos on youtube, but I could just take a chance.