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A couple of weeks ago I came across an Oscilloscope at work underneath a load of other junk. Once I had scratched my way through years and years of dust layers I plugged the over sized beast in and off it went doing what ever it was supposed to do. As I have said before on this blog my knowledge of electronics is limited compared to my experience with code. So although I knew my new toy would be very useful I wasn’t entirely sure why. After dredging up articles on google for about 10 minutes I had more than enough information to understand what this elaborate CRT screen was capable of. Although there was lots of information online about Oscilloscopes I found nothing that was quite so straight to the point and instantly gratifying as the video above that was recently posted on the Make blog.

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I didn’t want it to come to this! After many attempts to get the printer to go forward on its own accord (many resulting in ruining the control board and having to buy a new printer) i have brought out the secret weapon – ARDUINO.  I also bought a heavily geared down DC motor from Tamiya. These factors combined result in some serious direct to everything progress!

The video shows the printer stepping forwards at a pace set by the Resistance registered by a potentiometer. Later on the potentiometer will be very important in tweaking the printer so it outputs correctly. The DC motor has more than enough power to move the printer.

Circuit:

p1020053

The black and red wires go directly to the dc motor. The power is switched using a simple transistor.

Its been a really long tome since i wrote anything on here. This is partly because i am slacking and the mainly because i have 7 weeks left of my degree and have endless amounts of work to do. Just thought I’d take some time to document version two of the rhythm bug idea I posted a while ago.  Its a bit slow at the mo but works well. Gonna try different wheels maybe a different motor to see if i can improve its performance. I have also changed the switch to be more linear instead of rotating. This seemed to fit better into such a small space. One other detail that is worth mentioning is the humble Drawing pin. The contacts that slide across the circuit board are made from upside down drawing pins. They slide really well, conduct electricity really well and allow the contact to rotate with the movement putting less strain on the solder join – Useful little things!

Being quite new to hacking components i am completely curious about how the small things work. I have been on the hunt for a servo stepper motor for a while now just to experiment with and control using the Arduino. I was told that printers quite often have stepper motors in them so i blagged a printer and started yanking it apart in a rather brutal fashion. With components and plastic discarded everywhere i recoiled in disappointment. After reducing the poor defenseless printer into smithereens all i had to show for it was dc motors 😦 How then did the printer control the movement of the laser-jet so accurately?

Make magazine came to the rescue as always. Recently on there blog they posted a link to this blog :

A BIG MAGNET PICTURES FROM AN ACCUMULATOR.

A big magnet has a post explaining “Using a DC motor as a servo with PID control” which is what i have encountered when hacking my printer. This technology is not just in printers its everywhere. Its in your printer, Computer mouse, scanners and so much more. A DC motors and an optical encoder are used to replace expensive stepper motors. PID stands for proportional–integral–derivative.

Wikipedia says:

PID is is a generic control loop feedback mechanism (controller) widely used in industrial control systems. A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly.

If you are wanting to control movement from a motor and don’t want to spend on expensive stepper motors you should really consider reading this blog.

A big magnet

thank you Big magnet

thank you Make magazine

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