RS232 stepper motor control via unipolar drive board

[Sarah_UCL]

Hi KC, thanks very much for the schematic.

I think I should be able to construct a circuit based around that once I get hold of the component you suggest. Would this product do the same thing as the one you suggest from Farnell (http://www.maplin.co.uk/module.aspx?ModuleNo=2383&doy=31m10 - I have a Maplin store just around the corner). If not I'll just order the one from Farnell. I assume it is possible for me to take an RS232 cable and take it apart to solder cables carrying the signals I need to the 1489?

Now, assuming I can get this working, how do I specify to Labview which pin of the RS232 port to send the signals to?

Many thanks again,

Sarah

[K C]

Hi,

Stupid me    used the wrong connector layout.

When I build something at home I always adapt things to the parts I have so, the MAX232CPE is also OK, but you need 5 capacitors. You can find the datasheet here

You can use these C's from maplin (1µF/35V)

The pins at the RS-232 port in the schematic are the pin numbers from the connector on your PC.

To be sure that they are available (normally no problem) you can measure the voltage on the outputs pins.

Between 4 and 5 (and between 8 and 5) you should measure something between 5-12V.

You can drive the RS-232 signals with a property node. With the example you can toggle both lines.

I don’t understand why there two VI’s. I am sure you can do it all in just one nice VI. I also see a lot of things in these VI that should be wired different. Example the reference to the digital port is used many times where you should only have one reference. Did you wire these VI’s ?

If you have more question just ask.

 

Message Edited by K C on 10-31-2007 02:01 PM

[Sarah_UCL]

Hi KC,

Thanks very much for the updated schematic. I uploaded two VIs originally thinking that they were different. I only used one previously for control. These VIs were not my own originally, I've just included them as subVIs in my data acquisition system. Thank you for the suggestion of how to write the VIs for the RS232.

I'll get the components together and have a go. If I have any more questions I'll be sure to let you know.

Thanks very much again,

Sarah

[Sarah_UCL]

Hi KC, one more quick question. I'm going to try and get your design running the next day or so. If Iwant to run two different motors by the same design through the same port, can I use two of the other spare ports on rs232 to provide clock/direction to a duplicate system of MAX232CPE and capacitors?

Thanks,

Sarah

[K C]

Hi Sarah,

That is on of the drawbacks of the COM port. There are only two handshake output signals present at a COM port.

The two remaining ports in the MAX232 are transmitters (TTL to RS-232)

Since you don't have a printer port available, an other solution could be a USB interface chip. Never used it so I only can tell you what I will read in a datasheet. I think that's a bit to risky.

Is a second COM port an option ?

[Sarah_UCL]

There isn't a second com port. But the two motors do not need to operate at the same time - one is for a rotation, the other for a translation and the operation is 'rotate-step-step-...-step-rotate-step-step...-step'. The same type of motor is used to do each operation.

Could I include some kind of switch mechanism at the exit of the MAX232 to send signals to one motor or the other? Preferably this could also be controlled by the computer but it could be possible to do it manually (i.e. literally turn a switch). Otherwise, I could use another computer. Or would a USB-serial converter cable work?

Thanks,

Sarah

[K C]

Hi Sarah,

It's always a problem when providing a solution without knowing the application. Surprises when you think you'r ready 

If it was for myself (at home) I could think of something tricky with the data from the COM port but I don't have the time to build and test it.

With a USB-serial converter you have the same COM as you have now so with the same problem

But with a USB-serial converter you have a second COM port. Build the interface twice and you're there or not ?

[Sarah_UCL]

Hi KC,

The solution you have provided is great - I was initially only planning to control one motor via the laptop i.e. the one for which synchronisation is important. However, it did set me thinking that maybe I could use both. I'll try to get the first one set up and working then worry about doing a second.

Thanks again,

Sarah

[K C]

Hi Sarah,

If you can find the time, can you tell me a bit more about the application. Just curious.

[Sarah_UCL]

Hi KC,

I have the components all together now, I'll test the circuit on Monday when the computer is free.

The system including the motors is a first generation x-ray computed tomography (CT) system (see http://en.wikipedia.org/wiki/Computed_tomography).

Sarah