ScoCopTer (Feeder) V3

I realised while making the 3rd version of the ScoCopTer that I hadn't given a moments thought to the program and how difficult it will be to store the image in the NXT's memory as for one thing I am a complete amateur when it comes to programming having only dabbled in visual basic, and a little bit of C#. So I decided rather than dive head first into the photocopier I would just slow down a bit and make a Scanner first, program it and practice making the scanner as efficient as possible. Then I will make a plotter and experiment with making more complicated images, maybe print images from a computer in black and white onto the paper. The good thing about the Scanner and the Plotter is that they can both use the same base to move the paper and have the platform for the scanning/pen module to move across. This base module is what this update is about.

As you can see I've had two previous attempts at the ScoCopTer so I have learned some of the fundamental things about the design, and which methods are better than others for feeding the paper etc. I also decided to abide by KISS (Keep it simple, stupid) and as I still very new to the NXT system I am going to use all my Lego pieces with no limitations to give me a sturdy, well designed paper feeding module and I won't have to worry about not having enough pieces because I was only using NXT 2.0 parts.

The whole robot building is a learning process, and I've always dived in without looking closely at what I'm diving into, and it's only when I hit the bottom that I know next time to be a bit more careful and take things a bit more slowly. So from my original plan of a Photocopier/Scanner/Plotter all in one robot built from parts only from the NXT 2.0 set I have stepped back to a Scanner or Plotter using as many pieces as I need. Then when I have completely mastered the Scanner and Plotter I can move onto trying to combine the two to produce a working photocopier. One day I will learn that it's easier to start at the basics and build your way up rather that jump off a plane and hope to land at the top.

So clichés over, onto the Feeding Module (Feeder from now on), on the previous version the beams connecting the two ends of the feeder together was a lot stronger, but I found it awkward with both the motor and NXT at one end which made it look slightly out of proportion and the far end was a lot weaker than the side with the NXT. So I decided on this version I would have the motor at the opposite end to the NXT. Also with the previous version I tried to have the NXT mounted on top of the feeder which I was doing to try and allow the user to see the scanned image more easily, but in practice this was impractical because the NXT got in the way of the paper as it was being fed through, so this time I mounted the NXT on the end.

Here you can see a photo of the whole Feeder V3 before I look more closely at some areas of it;

Here you can see the overall model looks quite good and both ends are quite well balanced in terms of size and it's also very strong, I can pick it up from either end without it bending at all. Now I have allowed myself access to all my pieces I can use the small 'pulley' wheels on top of the main wheels to provide permanent friction on the paper as it's fed through but as the wheels can rotate that paper doesn't crumple or get stuck against it. The angled beam that the paper comes off is also a lot better than the last version as it isn't restricted be beams above it, or the NXT.

The drive for the feeder comes from the motor on the right which is geared from the motor 3:1 which obviously means there is more torque and less speed which is ideal for feeding paper. The motor is attached in a gear train form the motor going 8t:24t:8t:24t (t=teeth) and you can just about see this in the photo to the right.

In the way of the gear train you can see all the bracing that is used to lock the motor end together.

As well as the motor driving the wheels I also needed to attach some sensors so the robot knows when paper has been inserted, and also when the module riding across the top has hit one end so the rotation count could be reset so no error was carried forward. As in the previous version I used the ultrasonic sensor to detect when paper had been inserted and this was fairly simply connected to the middle of the structure, it also provided more support for when the machine was on a flat table and helped stop the middle from sagging. At the end with the NXT I have got a touch sensor which works with a quite simple mechanism to trigger it when either the pen or scanning module touches it. The touch sensor then bounces back into place with the use of an elastic band, and this took a surprisingly large amount of readjusting to get it to bounce back just right.
In this photo you can also clearly see where how I have used two wheels to to hold the paper in place, the top wheel is on a pivot that is held down by an elastic band - you can just about see the peg with the elastic band on the end of the 5 hole beam.

I have written a couple of short programs to test the feeder module and the only problem I have found so far is that the ultrasonic sensor doesn't really notice when the paper is less than 10cm away, it just has some problems keeping the motors going, so I may have to tweak this slightly or come up with a new plan altogether. But for now I'm going to work on the scanner module and hopefully I will have that built and programmed in the next week or so.

S

My NXT Scanner/Photocopier/Plotter V2

Sorry it's been a while since I posted on here, I have had so much school work i've struggled to find time to play with lego, let alone update the blog.

About this time last week I completed V2 of the All-in-One Scanner thing, which now thinking about it really needs a better name, so i'll call it the Sco-Cop-Ter from now on just to make it easier. The construction of V2 actually went very well and the final model was considerably stronger than the previous model, and also looked a lot better in my opinion.

However because it was stronger and better looking didn't mean it was functional, and that's where the problems began to start. The problems I had with the V2 are first I simply could not attach sensors where I needed them so I would not be able to tell where the robot or be able to reset it.

Here on the right you can see the design of this model. As you can see I had the motors placed vertically to try and minimise the lengths of the module and it worked fairly well, but unfortunately when programming I had no way of knowing whether the pen was up or down and no way to reset it because it was so difficult to attach any sensors. An ideal solution would be to have pneumatics/a linear actuator that could lower and raise the pen directly which also means I would not need to was space on the module with the awkwardly shaped motors.

Another problem I had with this model is that it really struggled to keep paper straight when it was fed through and it always crinkled. Below you can see the rear end of the paper feeder, and as you can see I have used the ultrasonic sensor to sense when paper is placed there and it will start turning the wheels to feed the paper.
Above each wheel is one of the angled beams which are pivoted and are held firmly against the wheels by rubber bands to keep the friction enough to keep the paper moving.

You can also see in this photo how I kept the pen module running perfectly straight across the width of the ScoCopTer. I used two 11 beams locked parallel to each other which successfully allowed the module to move back and forth nicely. But what I did not foresee is the beams catching on the 90 degree angle beams.

So this V2 version, although considerably better than V1 is still not really suitable for programming quite yet as there are still quite a few construction details that need to be ironed out first.

As this post has actually taken me so long to post I have in fact already built the base of the V3 module and all the sensors are already implemented and it is able to feed paper properly. But more details about that should, hopefully, be up over the weekend depending on the homework situation.

My NXT Scanner/Photocopier/Plotter V1

I've now had the Lego NXT set for just over a week and having done all the basic models I decided it was time to attempt something of my own. I attempted a Scanner earlier in the week and realised the programming for one is actually fairly simple and works quite nicely. As it was such a simple program I've decided to up the game a bit by trying to build a scanner that will store the coordinates in it's memory and then use it later on in the program to produce a photo copy of the original image. There are a few robots out there that produce a photocopy by having a pen run in parallel with the light sensor so when the light sensor senses black then the pen goes down, and when it sees white it goes back up again. This isn't really a photocopier but nonetheless it still works well and produces an accurate image.

I have spent about 3 days building this preliminary version of the scanner/photocopier and I decided that one of the big things i want to stick by is that I will only use pieces in the NXT 2.0 set so anyone can make it. There is a printer in 'The Unofficial LEGO MINDSTORMS NXT 2.0 Inventors Guide' by David J Perdue and Laurens Valk which uses just parts found in the set however it does not have the colour sensor attachment, you can see a video pf this printer in action here:
 http://www.youtube.com/watch?v=tNp62EfaJ60.

My first attempt at this model was not that great really, it was just to see if I could produce a scanner with the NXT 2.0 parts. The problem I had with my model is that the paper doesn't feed straight every time and the bar across the top sags slightly under the weight of the motors. Also the general build quality of the frame is very poor and not very strong at all. Below you can see an image of my first attempt.

Sorry about the camera quality the future photos should be better.

I'm going to completely scrap this model I think and the next model will have the motors vertically in the pen module to keep the length of the module as short as possible. I will also completely reconstruct the frame to make it a lot stronger. 

So hopefully in a few days I will have a stronger scanner that I can then start to program.

S