Gen 3 electronics -can anyoone clarify?

Hello all

Is there anyone who can point me to a resource that explains how and why the circuits do what they do?

cheers

Perhaps this is what you seek?

http://reprap.org/wiki/Electronic_wiring
http://reprap.org/wiki/Circuit_board_construction

Hi Nudel

Thanks for that, but no - that tells us how to build the board, but not why it works.

I am a novice as far as electronic circuits are concerned and am trying to learn how to design a board to do what I want it to do.

Part of the process is trying to understand how the Gen 3 boards work...

see here where I try understand the workings of the simplest board - the opto endstop.

cheers

One resource you may wish to explore is a circuit simulator. You can place components and link them up and simulate their operation, e.g. you could place all the opto-endstop components, apply voltage, simulate triggering the stop etc. LEDs will light up, you can place voltmeters and graph voltage, current meters for current, etc.

Here is one that I used in college:
NI Multisim
they have a demo version available here:
Multisim Evaluation Download

I'm sure there are several others, I just can't think of any right now.

Here is another huge resource, almost as much as a text book.
[www.allaboutcircuits.com]

Edited 1 time(s). Last edit at 05/25/2010 10:28AM by jeffpark_.

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[www.binaryconstruct.com]

AgeingHippy:

Trying to answer your question at a "high level"

There are essentially a few key parts:
1 - the main Arduino(Sanguino) CPU on the motherboard ( which is responsible for converting GCODE instructions into stepper motor step/direction information for 3 steppers on X, Y, and Z, AND the stepper driver on the "extruder".

2 - the "extruder controller" which is connected to the above CPU via a RS485 electrical connection, and it's job is to maintain the temperature of the extruder "hot zone" at the right temperature, etc. With "Makerbot electronics" this "controller" actually has an almost identical "CPU" on it ( a small Arduino Chip). Some Reprap designs avoid the second CPU, and use the first CPU for both jobs.

3 - the "stepper driver" units. there is one of these for each stepper motor. Each of these is responsible for converting the low-power digital step/direction information from the CPU into high-power higher-voltage signals that go through the stepper motors themselves, and cause the actual motors to turn in little tiny increments at a time.

4 - the opto end-stops. These are sensors who's job is it to make sure that they tell the main "CPU" when the stepper/s are about to try to turn further than the hardware is built for ( ie to prevent the motors from tearing the machine apar if they go to far in one direction. ).

Hope this helps,

Buzz.

Jeff & Buzz

Thanks for the response.

I have read a couple of electronics books, and think I am getting a little wiser, but a long way to go yet.

Am I correct in thinking the Gen 3 electronics are essentially digital circuits? Maybe with some analogue aspects thrown in at the stepper driver points to provide more or less current/voltage to drive the motors... perhaps most importantly the extruder controller? More voltage or current if the resistance increases when pushing the filament.

I struggle to figure out when DC or AC is involved...

Yes, you are correct:

* circuits are all DC. ( apart from the PC power supply, who's job it is to take AC, and supply the rest of the circuits with DC).

* All the core parts of the electronics are TTL digital ( which means they run at 5V DC ). THe stepper drivers allow this 5VDC digital signal to driver the stepper motors with a much higher voltage DC digital signal ( 12 v or higher ).

* The temperature sensor itself isn't digital, but its converted ASAP into a digital representation of the temperature by using a ADC ( Analog-to-Digital-Converter), so the digital logic can act on it.

* the electric "motors" that we recommend using now are called "stepper motors" because they have 4 wires, and each time you apply power to two of the wires, the sharf will turn 2degrees and then stop. to turn it another two degrees the wires you apply power to mush be changed to a different two wires. This change is done hundreds of times by the digital electronics just to make the motor turn one revolution. I'd encourage you to learn more about how these work, there are many resources available elsewhere on the net.

Buzz.