Worklog - The electronic part: The Sugar-Coffee dispenser controller (September 27 2010)
Following, i designed and made the PCB for the sugar and coffee dispensers. For this controller, i will use a doubled Unipolar Stepper Motor Full Step Controller that i had designed a couple of days ago. Because i have to control 2 motors, i will design one controoler and i will also include 2 relays to select each time which motor to drive. Of course, both motors will be able to run simultaneously.
So, here is the schematic diagram of the circuit:
The X1 connector is for the power supply. The SV1 is the interface to the main board, which will ultimately control all the modules. I use 2 relays, K1 and K2, to connect or disconnect the common wire of the motors. The relays will be controlled from the main board directly. Into production now:
The procedure is more or less known. First, the printout of the PCB
Then i cut the transparencies into size.
And i also cut a photosensitive PCB board to size...
...Which i smoothed its edges with a file
Transferring the artwork to the PCB with photographic method
Developing the PCB in the solution
Drilling a hole for hanging the PCB into the etching bath
This phenomenon worths to be mentioned. When i put the controller into test, it worked perfectly, except one slight problem: No matter which motor was enabled (by the relay), both motors would run! I could not run a single motor by no means! Then, i re-checked the circuit and found out what happened!:
Suppose that K1 is closed and K2 is open. The top motor should operate, while the bottom should be stopped. Now, suppose that a pulse arrives at the gate of Q2. The red line, indicates the normal current flow, through the top motor and through the Q2. The blue line, indicates the parasitic current flow. From the other side of the first coil of the top motor, an amount of current runs through, and goes through the other motor's coil! That is exactly why both motors run, even if the second motor's common wire is completely disconnected!
To resolve the problem, i soldered diodes on each of the 4 wires of the coils:
This way, the current will not follow the blue line, as it cannot go backwards to the second motor's coil. I soldered the diodes directly on the wires of the motors, because i did not want to re-make the PCB:
8 diodes and 8 pieces of heatshrink tube is what i will need
I cut the leads of the diodes small
And one by one, i cut the wires of the coils of the motors. NOT the common wire
Then i soldered the diodes with the correct polarity
And with the thermal gun, i shrink the heatshrinks
Done this for both modules
And then i tested the modules. they work perfectly! Now i can control both motors with a single controller, being also able to run them simultaneously.
@Alex In Greece during the Ancient times there was this saying: "Oyden monimoteron ek toy prosorinoy" which means that "nothing is more permanent than the temporary".
But now that you said that again, i think i should restart this project, shouldn't I? Hopefully within this year.
Hi you have a nice coffee Instant Cold Coffee Machine but you wanted to use a fridge for cold water but no water cooler that you use waron also in coffee automaaten is where you can get I know old water out of if not the name but it can look for you we have that built-in devices greetings alex
Hello George. Regarding the elements, these are hardware wiring to indicate wire connections between the modules. The orange boxes indicate wires coming from the output module (Digital Output Module - DOM), and the green indicate wires going to the Digital Input Modules. Notice that for example, from module "Rotary table", 4 wires comes out, then 2 of them arrive from the DOM and 2 goes to the CPU.
As far as the diode is concerned, this is only for polarity protection. It is the same as the D2. But you are right, It is not necessary and i may not put it after all.
I think your architecture diagram (first figure) is slightly confusing, because it seems to include elements of code (the elements above the CPU) with hardware elements. Ideally, you would have a system-level block diagram detailing your hardware and a separate functional block diagram to describe your code. If I'm misreading your architecture diagram, feel free to ignore this.
Secondly, looking at your reset circuitry, I see you have a 1N4148 diode between your microcontroller pin and your ICSP header (pin 1). I'm fairly certain this diode is not necessary, so you may want to double check that.
Frappé has become very popular here in the States. The difference is we use fresh coffee grounds to make coffee then we chill the hot coffee. But we tend to make more fresh coffee here while Europeans tend to make more instant coffee.
To serve we pour some in a glass and add chipped ice.
We also tend to add flavors to our frappé in the States. We can't leave a good thing alone - we have to tinker with it to make it more sellable.