Stepper motor focus control version 2

[ncjunk]

just ordered some driver chips for the stepper motor

I was building a stepper motor circuit to be driven from the parrallel port but got confused between my motors and had the motor that requires an H bridge type of control with a circuit that doesn´t.

So I had a look on the internet and found a driver chip that will work fine. So using my existing circuit I can add on the driver chips to control 2 stepper motors!

For anyone that is interested I am using the digital outputs from the port and putting them through an opto isolator as they don´t have enough power to do what I want. This signal then drives a higher power signal...which come to think of it I don´t need now...I feel a re-design coming on. Anyhow this output goes into the driver chip performs some magic and then sorts out 1 step for me.

Thing is....I found a usb IO kit with 5 inputs and 8 outputs and a couple of analogues...weeelll it would be rude not to buy it.

So this stepper motor will now be controlled via usb...probably an overdesigned opto isolator transistor circuit and finally a stepper driver chip.

When I have it working I will post all the details and the software to control it. (probably in 2 months time)

Neil C

[ribuck]

Hi,

I'd be quite interested in seeing how you get on with this as i'm looking to do a similar thing with my diy dome.

I've literally just started looking at stepper motor contollers today, and i cam across the following device.

Stepper Motor Controller & Driver: Virtual Village - UK

I presume you're planning some kind of similar dome automation.

What motors are you using or planning to use ? is there any specific type or rating you have found ?

Rich.

[ncjunk]

i have a roll of roof and the 3 bits of automation i am missing are weather, roof opening and focusing.

the stepper is the 42BYG006 see attached pdf 17 euros.

I didn´t see the circuit you mentioned but i am building one which will function the same. code, circuits, & construction :: Stepper Motor Control

i will code in visual studio to set outputs on the usb io card to send the pulses to the above driver circuit. speed will be controlled in the software.

with the stuff i have just bought the total is about 100 pound but i am playing, it could be cheaper, a bit. it will control 2 steppers.

Neil c

42byg%5B1%5D.pdf

[ncjunk]

the usb io module i am using is the following:- USB Experiment Interface Board : Experiment/Programmer Kits : Maplin

for controlling motors with this you would need a circuit to act as a switch to switch in the higher voltage required for the motor. The usb port supplies practically....not much (i almost put something else),,,,current.

you could just not buy this and use the printer port.

NC

[Reggie]

Hi NC, I'm surprised that you're not using an arduino board, as you're using a circuit from Tom Igoe's site Cheaper than the velleman, pre-built and loads of code already written for Steppers, Servos etc. with libraries pre-written for both.

[ribuck]

Hi Reggie, can you give some more details on this "arduino board", do you have any links or more information ?

Rich

[Reggie]

Hi Rich, the main page for arduino is www.arduino.cc

I am currently using the diecimila version (USB) it provides 14 digital I/O pins (6pwm), 6 analog inputs and serial I/O. It comes with its own programming IDE and also has a complimentary IDE for programming windows control of the board (although these boards work just fine without needing a PC) or you can program the windows side of things using serial and visual studio 2008.

I should add that any of the arduino's will be a lot smaller than the velleman too. The arduino's have a lot of hardware support, loads of little 'shields' that provide extra functionality, bluetooth, ethernet, RF wireless, gps, LCD screens, touchscreens, joysticks etc.

[ribuck]

I've looked at reggie's suggestion and the Arduino board looks fantastic and for £20 quid ready assembled it's perfect.

I'm impressed that it has tons of support on the internet, including pre-done software including working dll functions for incorporating into your own application.

Here's what i'm looking possibly looking at, but i will need to double check motor phase, amp draw etc to make sure everything will work ok.

Stepper Motors

Motion Control Products Ltd, For Stepper Motors, Servo Drives and all motion products

Usb Computer Interface

Arduino Duemilanove (Updated 328 Version) from Cool Components

Motor Driver

ArduMoto - Motor Driver Shield from Cool Components

Stepper Motor Controller & Driver: Virtual Village - UK

Rich

[Reggie]

It depends entirely what you want from the board as to which one to go for, the diecimila and duemilanove both have usb so are dead easy to update with new firmware (you write your own firmware, pretty easy though), the one you have chosen Rich, has double the flash (for firmware) and eeprom (for user settings storage, etc).

I've just ordered a Roboduino Mega from this guy on ebay, you may find a 328 version cheaper on ebay, cool components seems a little pricey. I've also ordered myself one of the LCDs on that page too, that way I can give myself freedom from a PC if it's needed

The Ardumoto shield doesn't do stepper motors I don't think. It's worth looking around, maybe adafruit has some?

Yup Here's one that definitely supports Stepper motors

and Here's a kit that has a selection of motors in it too. Hmmmn, looks like both require you to solder the components to the board.

[ribuck]

HI reggie, looked at that driver board which looks great but it only supports 0.6amps, i need to use slightly beefier mootors so i need something that will be able to drive 2 amps per channel / motor.

[ncjunk]

In one word...bollards....I wish I had known about that arduino board before.

I have a feeling I may get that board as well and I will find uses for both IO boards in something!

Reggi and Ribuck keep me updated on the progress as I love this kind of thing I find it interesting. This is the first time I have built a circuit since University and I had forgotten how much I enjoy doing it. There are always multiple solutions and there is always something you miss.

Good links Reggie.

Neil C

[ncjunk]

Ok, I have just bought the Roboduino Mega from the same ebay guy and the LCD display.

You are correct that the Stepper Circuit mentioned above is limited to 0.6 A. It uses the same chip that I have bought from Maplin the L293. As one person put it to his students, connect your motor to the circuit and run it whilst touching the chip if the chip gets too hot to touch you have the wrong motor! (I think he just enjoys inflicting pain).

Neil C

[Reggie]

Hi Ribuck and NC Ribuck, for the stepper motors, I would jump on both of the adafruit and arduino.cc forums and ask for some advice, you may find that there's a less expensive and more elegant way to get more power for your steppers, my citcuits are fairly minimal at the moment and I haven't managed to get hold of a cheap (free) stepper motor to play with yet, my diy focuser uses a continuous rotation servo which the arduino can drive directly (5v,gnd, Signal).

Funnily enough NC, my Dad had bought one of the velleman kits (he's way better at soldering at 60 than I am at 40 ), I borrowed it for a couple of weeks and decided that it wasn't quite up to snuff.

I believe the velleman kit is just really an expensive 'badged' PIC development board which is pretty similar to the Atmega chip development boards (arduino), although the atmega's seem to offer more of everything in a much smaller package.

The arduino is a great way to learn about interfacing with input sensors (buttons, knobs, sliders, temperature, humidity etc.) and outputs (LEDs, motors, sound, LCDs etc.) and simple serial comms.

At the moment I seem to keep building circuits on breadboards, then breaking it down and building something else, having a lot of fun learning

So far I've built:

An automatic dew heater (senses scope temp and ambient temp and adjusts the scope temp accordingly) works standalone or with a windows gui.

My latest 'project' was to build a 'tactile midi controller' for controlling music production hardware/software, a bunch of knobs, sliders and buttons, with a couple of rgb leds to indicate what was happening.

Next I will look at controlling my servo focuser, the code for servos is so easy to use I'd skipped this project for now for something a little more challenging.

my other plan is to add the LCD screen to give standalone visual feedback for anything I am doing, it'll be great for debugging.

[ncjunk]

I decided to go for the easy focus controller first as my entire set up for astrophotography is automated (apart from the observatory I still have to manually go and open the roll off roof).

If you could PM any automatic dew heater information you have that would be great as that is next on the list after focusing. I think I could have Focus control and dew heater control off of the same Mega board (Must be possible). I understand the heater element for the dew heater is just a load of linked resisters (after all you are only looking for a small injection of heat to the scope to stop it dewing up).

I got the LCD as well as like you say it will be good for debugging and comes with 6 buttons on it. They will be good for something, perhaps manual override of the focusing.

I am looking forward to getting all of this now!

Neil C

[Reggie]

You guys maybe thinking to 'big' for the stepper controller:

Arduino - StepperUnipolar

or

Arduino - StepperBipolarCircuit

or the tom igoe site that you've been looking at NC:

code, circuits, & construction :: Stepper Motor Control

all give much simpler solutions than the motor shields, the unipolar arduino tutorial requires minimal parts. The steppers on this page (with exception of the 6V version) are all under 0.6a so should be fine with the L293 IC, looks like an L298N will do up to 3A so you should be good to go whatever way you choose to do it.

I've just thought of a nice little project, cheap head tracking for video goggles in stellarium/starry night, would be nice to look outside in LP skies and see what you are meant to see etc.

I want to add some kind of wireless comms. to the arduino not sure whether to go bluetooth or simple RF though.

[Reggie]

I'll dig out my information for the automatic dew heater, I've already made a simple pwm heater circuit that powers both my dew tapes, using an incredibly simple 555 timer, runs completely standalone, from that I really need only the TIP120 transistor + a little circuit, the arduino and some code to control the PWM, I've written everything else. I would like to switch out the temperature sensors for something that does below 0 with a positive voltage too.

The arduino mega should be fine doing a few things, it can be interrupt driven too.

[Reggie]

Here's the ridiculously simple sensor circuit drawn in a childlike manner

[Reggie]

I knew I'd seen a board somewhere that suited your stepper motor needs without fiddling too much:

Take a look Here.

It'll give your motors up to 2A each, and provides some buttons on the board for speed/direction etc.

[ncjunk]

Cheers Reggie,

I have a shed load of bits now so I will be putting it all together over the next month. Off to the UK on Friday for a weeks holiday and to pick up all the stuff I have sent to my parents in the last week!

Neil C

[Reggie]

Hi Neil, Let me know how it all goes, if you need any help coding anything give me a shout, btw. if the 'processing' windows gui app. feels clunky, I've got a version that I wrote in visual C sharp too, I'm happy to share absolutely any of my code or talk about code ideas

[Chris Rowland]

I've made a stepper motor driven focuser using a smal geared stepper and an Arduino with an interface board using a ULN2003. This will handle 500mA. If you need more power then bigger driver darlingtons or MOSETS are easily available.

I like the Arduino. I use the Freeduino, they are even cheaper. The Arduino development system is pretty easy but capable. It's easy to do simple interface circuits and it looks like a serial port to the PC so it's easy to interface to it.

Chris

[Reggie]

They are interesting little boards, there's a lot of code/project examples so its very simple to adapt to suit your circumstances.

[ncjunk]

Cheers for the PM with the connection details. Makes it much easier when you know that each board follows the same Connector layout.

"Hello World" printed and working fine

Neil C

[Robfal]

Funny old world isn't it. I too have just bought an arduino board to make a stepper driven focuser. Not yet had a chance to play with the programming yet, I could find that aspect a little daunting although I have dabbled with PICs for several years.

It might be good to pool our energies and produce a SGL focuser; am sure all of us have different skills we could offer.

It would be especially good if we could interface it with an ASCOM driver then we could use focusmax etc. This is possible I think 'biopic' managed to get his homemade focuser to use the Robofocus ASCOM driver; he has sent me the info and code however my C+ coding knowledge is pretty limited.

I'd certainly be interested is help out or 'pinching' other peoples ideas. By the way I'm a Head of Technology at a large secondary school (and an engineer) and so could offer a range of things. Rapid PCB manufacture/ electronics. I also have a Laser cutter, mills, lathes, simple CNC and print sublimation equipment. And probably some other stuff too

Rob

[ncjunk]

Rob,

I was thinking something similar it is nice to know you want to do the same thing.

Reggie and I (correct me if I am wrong Reggie) are looking at the following:-

1 Dew Control

2 Focus Control

3 Cloud Detector

The board is relatively easy to program and the examples provided are excellent. The board layouts were difficult to find information on but once reggie pointed out the layouts were the same between boards it all made sense.

Reggie has done some Dew control software and is also writing an interface for the PC. The focus software will be simple to begin with, we will get it going forward and backwards, and then we will aim to interfeace with ASCOM. I understand there are required signals for ASCOM compliance but don´t know how to do it.

The information that you have could be usefull for that.

The Cloud sensor will use an IR sensor to detect if it is clear or not but I haven´t looked at the circuit requirements (Op amp? no Op amp? etc). I have attached the datasheet for 1 IR sensor but there is another available from Farnell and RS which might do the job.

Looking at the datasheet there is an op amp circuit design there which may or may not be usefull.

I think the focus side will be easy once we can determine what is required to interface with ASCOM.

The IR sensor needs an interface circuit designed and then we will use thresholds to determine if it is cloudy or not.

That leaves the point of how to control all the information. Shall we start a new thread which is more allong the lines of Arduino Dew, Focus and Cloud sensor? Also I think it may be usefull to start a doc with all the information we have to date for each section.

Let me know what you think I am not bothered how we do this or who wants to play with what. This is just a bit of fun for me

Neil C

TP336x.pdf