First of all happy new Year to all readers of this blog. Let this Year be better than the previous one :).
I thought a lot of this post and of my next step in the stepper motor driver which will control my cnc drill. Actually there are some things going on. They are not going very fast, but many of them at the same time. So I would like to sum up my achievements and ideas and findings although the solutions they present will not be used in my future work. Still it can happen, that someone (including myself) will find them interesting and useful.
So lets get on with the topic.
In the previous article I presented the Circuit board with elements on it. One of the most important sentences in that article was about the pin headers which are used to steer the transistors.
|Image 1. The PCB.|
|Image 2. The modified exciting sequence.|
|Image 3. Exciting sequence from the perspective of the driver|
In the 1'st step the inputs that will be steered with 5V are A and E. That means, that the remaining inputs (B, C, D, F) will be steered with 0V. The A and E match the U+ and V- of the driver inputs. The transistors steered with 0V do nothing (conduct nothing, they are OFF). The ones, that are steered with 5V will conduct the current from the drain of the transistor (the middle leg) to the source of the transistor (the lower leg, if the transistor is oriented like the Q4 in the image 1).
So at a time, we are steering only 2 transistors, the current flows from + of the J1 to the - (Yes I know, this is not exactly true, but lets leave this alone).
The next table shows the explanation presented above for all driver inputs.
|Image 4. The basis for the Karnaugh minimisation.|
|Image 5. Minimisation.|
|Image 6. Transformation. Done using eqneditor.|
|Image 7. Circuit build from the minimisation.|
- 6 times 2 input AND gate => 2x quad 2 input AND 7408
- 3 times 2 input OR gate => 1x quad 2 input OR 7432
- 2 times 2 input NOR gate => 1x quad 2 input NOR 7402
So to avoid all problems connected with the idea above I decided to solve this problem in a different manner. I am not sure if I will state the truth now bit I will try. The easiest solution for my problem here is the usage of PCF8574.
But that is a topic for the next post which I will write as soon as I order the micro controller and test it for a while.
PS. For all who are interested in the details of the PCF8574 please visit this or this (caution the second link is in polish).