Usborne Electronic Workshop

[Alun]

Just found my old Usborne Electronic Workshop book "How To Make Computer Model Controllers for C64, VIC 20, Spectrum & BBC". There was also a robot one in the series but I do not have that.

Re-reading the book now I still remember doing some of the projects over 25 years ago.

The book is a good mix of practical hardware, coding and "fun" things to do.

For instance sensors are made using nails and drawing pins as contacts (the child can therefore see the switch working instead of just buying a microswitch).

There are good chapters on the theory of relays, resistors etc.

Everything is soldered to Veroboard so, again, the circuits are easily traceable. Instructions are included for making the cables to connect to the user ports of the computers - along with dire warnings about wrong connections ;o)

The programs include allowing trains to be found on a track, races to be run, "fuel" to be added to scalextric cars (the power is cut if you run out of fuel) etc.

I think these type of exciting "real" projects are ideal for the Pi (& Gertboard) as they allow children to experiment and play with real hardware and immediately see the results.

Perhaps a community-contributed library of starter projects will inspire the current generation of children. My 6 year old loves machines and robots - we will both be playing with my Pi when it arrives & doing very similar things to those in the book.

As for the programming language - I don't think it matters. Use the one most suitable for the project - the logical thinking is the important and difficult part, the nuances and syntax of a particular language are easy to learn. Personally (although I am an Engineer not a programmer) I started with the ZX81, then BBC Basic, FORTRAN and various object oriented languages. I use the tool for the job, sometimes it is a properly coded application, sometimes just a quick and dirty bash or powershell script. Last week I dusted off my FORTRAN skills and wrote a couple of applications for a client that saved them hundreds of hours of manual data manipulation. Why did I use FORTRAN? They use specialist software written in FORTRAN which uses formatted input without robust error checking. As I don't have the source code for the specialist software I analysed the required formats and used this to write FORTRAN format statements to generate text files in the required format. This was easiest in the same language as the original application.

[croston]

I built the robot from the book you don"t have in your collection. I still have it and am looking to convert the software to Python for a R-Pi. The electronics should need little or no modification.

[nickorossa]

Hi

I may have had the book to build the robot too. However searching for the book on google showed an unfamiliar cover. I pretty sure the book I had didn't have the grab arm robot, but my memory may be playing up. It was some 25 years ago.
http://biblio.co.uk/books/287181026.html

The circuit board from what I remember has 3 miniature relays (1 SPDT and 1 DPDT), some transistors and resisitors, possibly a diode or two. The two DPDT relays controlled the motor direction. There were two micro switches which detected if it hit a wall.

Does that sound familiar with the robot in the book?

I originally built it using lego, but never finished it because I could never get the connector to connect to the expansion port of a Commodore 64. I'm planning to build a new version once I have the time to build the circuits.

Nick.

[Alun]

The link you sent is to the correct book. The robot has a grab arm.
The circuit has 5 relays, some transistors, diodes, resistors, a potentiometer and a light dependent resistor.
The robot has simple sensors to give feedback as to whether the arm is up or down and whether the gripper is open, closed or holding something.
The potentiometer adjusts the sensitivity of the light sensor so the robot can be made to follow a black line on the floor.

Forgot to mention - I have bought the robot book now. £2 on Amazon.

[nickorossa]

Hi

Thanks for the reply. If the circuit has 5 relays then its definitely not the same one that I had many years ago. Perhaps the one I had was an earlier edition and therefore a simpler robot without the grab arm.

I picked up a copy of this book on eBay for £2 and it should be delivered in the next couple of days. I'm sure when I checked Amazon it was listed for much higher prices; £15+.

Either way I foresee a few days/weeks/months spend in the garage playing with stuff to try and get it working

Nick.

[nickorossa]

I managed to track down the book that I had, which was this one.

http://www.amazon.co.uk/Things-Computer ... 27&sr=1-87

Getting a copy, now that may be a little harder!

N.

[Alun]

I have been translating the shopping list int he book to parts I can get now. Mostly easy but the relays were the most difficult.

Winter project coming on

I am thinking that the robot is big enough to carry the Pi with the whole lot being powered by a rechargeable battery pack. Possibly be able to control it from my tablet using SSH over wireless.

[nickorossa]

Hi

The diagram of the relay is a little different to most SPDT relays I've come across which have 5 pins. As the book says you can use alternatives which wires to map the pins. Both RS and Farnell do 5 pin versions.

One thing I noticed about the robot in this book (at least from my understanding) is that a single relay controls motor direction (all motors) and then another relay is activated to indicate which motor is being spun. This makes the whole thing rather linear. There is no circuit diagram so I'll have to reverse engineer the circuit board.

In the book I originally had (waiting delivery), the drive relays were DPDT which meant that the single relay controlled the direction of each, and a separate DPST relay controlled whether the motor was powered.

Sounds like we have similar projects for the winter, although in the first instance I'll use technical Lego to build the robot since it should make it easier and the kids can be involved (not good to let a 4 year old play with a mitre saw :o ). I think I'll merge the circuits from the two books and try to enhance it with additional sensors and speed control.

I think its going to be a long winter :D

N.

[psutton]

I have practical things to do with a microcomputer, got some stuff like led displays etc,

[lapoltba]

I love this.... These are great projects for the Pi and it's educational goals! Heck, i'm 26 and I'm thinking about building them.

[nickorossa]

I have been translating the shopping list int he book to parts I can get now. Mostly easy but the relays were the most difficult.

Winter project coming on

I am thinking that the robot is big enough to carry the Pi with the whole lot being powered by a rechargeable battery pack. Possibly be able to control it from my tablet using SSH over wireless.

Did you find the relays, if not these may be suitable and have the same pin layout. They do 5v, 12v and 24v.
http://cpc.farnell.com/_/hrs1kh-s-dc5v/ ... tt=sw03273


Regards.

N.

[Alun]

The ones I found were:

http://uk.farnell.com/te-connectivity/v ... tt=1175004

These look the same to me but I have not fully read the datasheet. I'll look at the ones you suggested as well.

I can't understand why the Farnell & RS "equivalent" to the recommended Fujitsu FBR211 B or E relays are completely different in size and pin layout. I think the only equivalent is their current carrying capacity.