Hi people,

I'm a newbie here and quite a green one at that so please be gentle! I'm trying to build a project and the thought process behind it is quite simple. I'll try to itemise it as well as I can.

I need a system which will rotate a sign 360 degrees, stopping at each 120 degree increment. In order to make it go to the next 120 degree position a button must be pressed. Thats it!! I'm guessing I'm going to be into a stepper motor but I don't know anything about PICs or programming them so I really do need your help and advice.

Really looking forward to the replies.

Oh for reference this is what I need..ish..., but with only one button and one direction of travel.

Thank you everyone!

 

How much rotational inertia does the sign have (how big is it, how much does it weigh)? You might have to have a slow-start, slow-stop ramp-up, ramp-down, type of drive. It also effects the sizing of the motor.

Easiest way of doing this is by using an Arduino. Use a stepping-motor interface pcb with it...

 

Well it's only a small foamex sign probably weighs about 100g and is 10' high and 5' wide on a horizontal rotating bar with ball bearings at one end and whatever will be driving it at the other.

It needs to be stand alone as in motor, chip, button, power supply. It has to be mobile you see.

 

If you do not need any kind of rapid operation keep the rotations as low rpm as possible and you should have no problem.
Keep in mind also that most S.M. increment in 1.8° steps (200 steps/rev) unless you go to micro stepping but torque will decrease.
Max.

 

Since most steppers require 200 steps per 360 deg, you will have to build a state-machine (counters) that generate 67 pulses, wait, 67 pulses, wait, 66 pulses, wait, ...

By the time you do this with CMOS logic, you will wish you took my advice and learned how to use an Arduino mini, which looks like this:

 

If the angle and rotation speed aren't critical you could probably use a simple geared brushed DC motor with 3 cam-operated microswitches at 120° intervals.

 

If the angle and rotation speed aren't critical you could probably use a simple geared brushed DC motor with 3 cam-operated microswitches at 120° intervals.

Now that sounds simple, any ideas on how to approach that?

 

One advantage with a stepper over a DC brushed if this might be an issue, is the stepper has holding torque when stationary, even when not powered there is indent torque.
Max.

 

A highly-geared DC motor, e.g. using a worm-drive, may/will provide enough frictional torque when unpowered. Is this 10' x 5' "sail" exposed to wind or jokers? How fast does this thing have to rotate?

 

Can be easily done with a stepper motor. I can write a code for you but you have to mention the step angle of your stepper motor.

 

Hello and thank you! I've been looking at a 7.5 degree stepper motor as I can get it to turn to 120° exactly without altering steps here there and everywhere. The only trouble is I don't know what driver to buy, to be honest I'm a bit lost with this and really need help to get this to work.
Here is the link to the stepper i'm considering...
http://www.ebay.co.uk/itm/New-Phili...aspberry-Pi-/121362990635?hash=item1c41cc462b
Many thanks for your help!
Rich

 

ULN2003 can be used to drive your Unipolar stepper motor. Your motor power rating is 2W. P = VI. I = P / V = 2W / 12V = 167 mA.

https://electrosome.com/interfacing-stepper-motor-8051-keil-c-at89c51/

 

Please forgive me for sounding ignorant but what should I do next? I feel pretty out of my depth. if it was electronic components or solid state stuff I'd be fine, but programming chips is where i get totally lost!

Ive had a look on eBay and there seem to be several of these driver boards available but all with differing descriptions. Which should I be purchasing?

 

Buy an Arduino should be easy.
https://www.arduino.cc/en/Reference/Stepper

 

Buy an Arduino should be easy.
https://www.arduino.cc/en/Reference/Stepper

So maybe I wasn't clear at the start, I don't want to have a micro controller board as such. If you take a look at the video at the start, thats all I want.

I want a switch, a stepper motor and the end result in a 120° turn from the motor. It's going to be in a vehicle with no boot up time whatsoever. It needs to be a hardwired solution, no controller board. I don't know if this can be done without a raspberry or auduino which is why I'm asking here.

In the video at the top of the page I see no controller board. Just a switch, chip, stepper and momentary buttons for various positions. This is EXACTLY what I want!

 

In the video you linked above he is using an AVR microcontroller. It can be done using discrete components but it's not going to be easy and will probably end up costing more than MCU solution.

 

So you just need a 0-16 count steps then reset, there are a few ways, one is using J-K flip flops driven by a 555.
Max.

 

So if i was to use an AVR would anyone here be able to programme it to use the stepper I mentioned earlier. I notice the one in the video is a 5 wire and the one I'm looking at is 6. Would this have any impact on the setup?

I assume the controller is preprogrammed and once power is supplied it will simply do what its told until power is disconnected? Sorry for sounding thick, it's all very new to me.

If the method demonstrated in the video is essentially a stand alone, add power and go, system. That's what I'll go for! I'm quite happy to pay someone to programme it and set it up if it comes to it. Once the programming and setup is done, I'll build the mechanical system to rotate the sign.

If anyone has any better ideas on stepper motor I'm all ears, but please treat me as a novice, because thats exactly what i am!

 

If you have no idea how to control the stepper motor, check this --
Stepper Motor Forward And Reverse Testing circuit, and turn the conception to your uC.

 

There are multitudes of 0-16 counter circuits out there, 7.5° steps for 120° is 16 steps.
http://www.edutek.ltd.uk/CBricks_Pages/Counter_Binary.html
Max.