Worklog - Improving the mixer rising-lowering mechanism (June 23 2010)
In the third page i presented the mixer mechanism along with the rising-lowering system. That was incomplete though, as the limit switches (high and low) were missing. I also decided to make a linear encoder to have an approximate position monitoring of the mixer. So, first the linear encoder. A ready-made linear encoder costs a lot to get. After all, they usually come with a high precision of some tenths of a millimeter, something that i do not need. So i made one myself, with an unused spare part from a CNC (a Balluff metal detector) and some screws:
I drilled a hole for the sensor to fit in
First i put a pencil inside and moved the mechanism all the way side to side
This way i had a straight line drawn on the base wood, directly at the center of the sensor hole
I used the caliper to mark equal spaces around 10mm each
These are the marks.
In each mark, i drilled a screw.
The first half of the encoder is ready. Now i had to fix the sensor inside the hole. The sensor will send a pulse each time that it is close to a metal (like the screws).
This is the sensor that i am about to use for the linear encoder
I put it inside the hole. The sensor has a sensitivity range max 1.5mm. So the distance from the screws is critical. Not too big as it will not work, not too small as it will crash.
This is the final assemble. I did not use the connector of the sensor as i did not have one right now. So i soldered 3 wires (+ - and signal)
The hardware limit switches!
Each CNC axis has two means of overrun protection: the software limit switch and the hardware limit switch. The first one is -as named- controlled by software. In my example, i know that from top to bottom i have 17 screws, so i expect 17 pulses to arrive. During the rising operation for example, when the controller reads 17 pulses, it will stop the motor as the head is at the top. But what if this procedure fails for any reason? Then the hardware limits will save the day. The hardware limit switches is -as named- hardware switches placed at the two sides of a shaft. They are usually located a little bit further than the software limit switch, and they control the power of the motor directly, not through the controller. If any of this switch is actuated, the power of the motor is immediately cut-off because it means that the head is about to go out...
I will use 2 L metallic pieces
From which i shortened one side
I screwed one on each side of the mixer wagon, about 3mm distance from the base
This is how it looks with both L profiles screwed
I had once ripped some switches from a pinball game... Very useful items
I removed from both the metallic extension. With the wagon about 5mm from the top side, i fixed the first switch...
...and the other switch at the opposite side with the wagon about 5mm from the bottom.
When the wagon is about 5mm from a limit position, the switches will cut off the motor power supply (NC contact) and will inform the controller (NO contact)
@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.