Automatic Warehouse Model

Support Motor controllers/drivers and motors
1

Hi!

I’m trying to make an Automatic Warehouse Model.

I bought:

The principle used is as that of the CNC routers => ball-screws.

To control the system, I’ll use microcontrollers (PIC16F887 or PIC16F877 … I have 2 of both).

I’m thinking of using 2 optical sensors from some scrapped mouses: the coder/wheel (scroll) attached to a wheel of the transelevator acting as a counter for column aligning and another sensor used with the coder from a scrapped printer (that bar that looks transparent) acting as a counter for line aligning checking.

The problem (misunderstanding) that I have is that I don’t fully understand the specs of the power supply needed. I’ve read that those motors support those drivers and I thought of a 12Vdc voltage for each of them (3). But, I don’t know the current needed for the driver (each), nor if 12Vdc is enough. I know that the driver has a maximum current output of 2A (more than those of the motors).

I’ll use all those motors in bipolar configuration. I’ve read that I need to limit the current supplied by the driver to 70% of the maximum rated current of the motor.

I’ll use independent and regulated outputs (power supply). I’ll design the power supply myself (220AC to … whatever specs you recommend Vdc). Considering your recommendations, I’ll chose from a Forward, Flyback or Push-Pull configuration with each independent output as those explained by you (voltage and current). I know that I need 5Vdc for the reference … am I limited by the current? If yes, what is that value?

I’m a newbie when it comes to stepper motors and drivers for them. Since I’m not experienced enough to comprehend the specifications needed by (output) the power supply (to be designed by me), please help me understand the process in order to be able to start designing it … and finish the project.

I’m thinking of using JAL (v1 or v2) to program the microcontrollers (I’ve tested the procedures needed with virtual instruments) … I’m not accustomed with C for mctrl. I know C++ … but I’ve used it for OOP = Object-oriented programming (no external hardware involved; only the PC).

Thanks!

P.S. Sorry if the thread is in a wrong topic (I think not). If so, please move it where it belongs. Thanks again!

2

Hello.

It sounds like you don’t know much electronics, so designing your own wall-powered power supply seems dangerous and unnecessary. The currents given are per coil, so doubling that should be a good value to use per motor. However, if you’re using a supply that’s a lot higher than the motor rated voltage, the current from the supply will be lower. So, for the second motor, for instance, a 5V, 2.5A supply or a 12V, 1A might be rough minimums you should use for your power supplies. For the 5V supply, just a few tens of mA should be plenty (it’s not just for reference: that’s what the chip is running on).

I think you’re mixing something up on the 70% figure; that has to do with figuring out what the current is set to; the peak will be 100%.

- Jan

3

Hi, and thanks for the reply!

I’ve seen the driver’s datasheet and knowing that the driver uses 2 H full bridges with enhanced MOSFET (n-channel) I was confused. I know that a MOSFET drain current has a formula like this: Id=Idss*(1-Vgs/Vt)^2, where Vt is the threshold voltage. Knowing these, and reading that post, it got me confused.

To avoid more misunderstanding, let’s talk specifically:
[ul]

[li]Stepper Motor: Bipolar, 200 Steps/Rev, 28x32mm, 3.8V, 670mA

This one should need at least 7.6V, right? I will limit the current using the potentiometer from the driver to 500mA per coil. I know that I should use a lower current than the one specified in order to avoid damaging the motor. I chose to use a 12V output from the power supply (there are more and they are independent). A higher voltage should not be a problem, since is lower than the maximum rating of the driver … and, as said in the FAQ post for the steppers, it should mean a faster ramp up for the current. No problems until now.

As explained by you, If I use a 12V at 1A delivered from the PSU to the VMOT terminal of the driver, each output of the driver should have a 0.5A current, right?

If this is so, then I think that I understand the specs needed in order to design the PSU. If else, I’m back to nothing.
[/li]
[li]Stepper Motor: Unipolar/Bipolar, 200 Steps/Rev, 42x48mm, 4V, 1200mA

If the reasoning is correct, then I will need a 12V at 2A (the current for each phase is limited to 1A).[/li][/ul]

For the 5V output from the PSU I will need a few mA (200), right?

~

So, with these being said, my PSU should have these outputs:

  • 1x12V at 1A;
  • 2x12V at 2A;
  • 1x5V at 200mA.

Did I get it right? If not, please explain with details using as example one of the steppers that I am using.

Thank you!

4

You have a lot of mistakes in your post. It seems like you think you always need double the motor voltage, which is not the case. Separately, the motor driver needs at least 8V, so your 7.6V is not valid for that reason, too. For the unipolar/bipolar motor, I don’t know what the 4V rating is; it’s possible you need 8V to get 1200mA into it in a bipolar configuration. (That is the case with our item # 1200; if you are talking about motors we have, please use the item numbers.)

Your final requirements list is about right, though you don’t have to use separate supplies for the different motors. So you could get by with a single 12V, 5A supply and a smaller 5V supply.

- Jan