Thursday, May 26, 2016

Tasman Turtle - Restoration




After all the time I spent trying to find information on early turtle robots I didn't think that I would ever get to see a working Tasman Turtle. The ones I knew about were incomplete and non functional. I wanted to put one together but even if I had been able to get my hands on one, due to lack of information, I would have struggled trying to restore the thing. That is why a few years ago I built WALTR, a LOGO turtle robot, using modern day components (http://lukazi.blogspot.com.au/2012/01/waltr-introduction.html, http://lukazi.blogspot.com.au/2012/04/waltr-update.html). This is well and good. WALTR can do more things and do them easier than an original turtle robot but it just doesn't command the same presence. Well, this year that all changed. I was extremely lucky to have come across this particular Tasman Turtle for sale. It was non functional but all the main parts were there, including documentation that I had been trying to find for a number of years. The gentleman that I purchase it off, Chris, told me the story of how he had saved the robot from ending up in a dumpster and ended up storing it for fifteen years. Thank you Chris for making this fabulous piece of Australia's education history available. I figured that if I didn't pick it up then it may have ended up sitting in some collector's garage for the next few decades. My aim was to restore the robot, document it and share the information.


WALTR and his old mate Tasman Turtle.



The first step in the restoration process was to find out if the floppy disks still worked and if so then the information that they contained. In a project such as this, getting the software working is just as critical as getting the hardware going. Looking at what was in front of me, I had a pretty good idea of what I was going to be dealing with except knowing what was on those floppy disks. With floppies you never know what you are going to get until you do the restoration. Floppies are also the most likely part of the system to have failed. Saying that, I have had a greater rate of failure with my 3.5inch floppies than I have with the 5.25 inch ones so this gave me a bit of hope that the data was still there. However when I noticed how warped some of the disks were and the magnetic part would not spin around inside the disk jacket, I had grave concerns. Before attempting to cut open the disk jacket and place the inner magnetic disk into an alternate jacket, I thought I would just try them out as they were. It turned out to be just fine. From the provided three disks, two sides were not used, one had an incomplete copy protection program on it, one contained a few simple primary school games (this side was corrupt so I was unable to extract all the software from it), one had the Tasman Turtle Robot LOGO procedures on it and one contained the Turtle Programming Language software (I later worked out that this is a screen based turtle drawing program and would not be used with the Tasman Turtle). Therefore only a single side had any relevance to the robot. It contained setup software which helped out a lot but unfortunately no project examples like I was dreaming of finding.



Scanning the manuals to PDF was next on my "to do" list. This was a straight forward exercise and it was something I was able to do while waiting to sort out the turtle's power supply situation. I also found a few broken wires on the turtle but it wasn't difficult to work out what went where. It was a quick and easy job to clean the wires up and resolder them.



The robot uses the Apple II for control but to drive any of the robot parts requires an independent 12V power source. This robot did not come with a power supply so I needed to source or build one myself. I was thinking about purchasing a modern day regulated 12V 2Amp caged power supply. This would have been the simplest thing to do however it would have looked out of place with the Apple II and the robot being the age that they are. I decided to try and track down an age specific power supply and it was not too difficult to do so. I picked up a Panther Power CB radio power supply which would have been a typical power supply used with the robot in its day. Anyone who was into CB radios back then would have had at least one of these, or something similar, lying around in the back shed. Even though it gives out 13.8V this is still well within specification for the turtle robot. However being the age that it is I didn't want to stress out any of the turtle's components more than I needed to so I decided to make a simple modification to the power supply. The power supply's generic printed circuit board makes this very easy to do. This allows me to vary the voltage from 11V to 15V. It's currently set around the 12V mark.

Once the power supply was sourced and modifications were done I had to perform three smoke tests.
  1. Power on just the power supply. Great, no smoke.
  2. Power on the power supply and robot with the card unplugged. Great, no smoke. Crapped myself on the solenoid engaging (I wasn't expecting it to be that loud). I also thought something was wrong with the speaker because the horn was stuck on. I later found out that this is normal although very annoying. The horn becomes silent after loading the LOGO software.
  3. Power on the power supply with the robot and card plugged in. Great, no smoke.

It took a little bit of time to get rid of those cob webs out of my head and refresh my LOGO language knowledge. While playing around I found that the Apple LOGO Tool Kit disk also contains Tasman Turtle LOGO commands but a more comprehensive version than the one I received with this robot. It contains commands to change the slot location of the robot interface card as well as the extra commands needed to drive the extended Tasman Turtle features such as the Electronic Compass. I didn't have to use LOGO. Using Basic or Assembly would have been just as suitable however because I already had the LOGO setup examples it fast tracked getting the turtle going.

Once that was done I was able to test out the robot's features. What I didn't realise is that during the smoke tests I had removed a screwdriver from my hobby box which was holding up the robot, allowing the wheels to move freely. Therefore the robot ended up being placed directly onto the table. My first test was the move forward command which worked well and all I saw was the robot heading straight for the table's edge. I jumped over the table and grabbed the robot just as it was heading over. The project was nearly finished even before it had a chance to get going. I'm lucky the robot is no speed daemon. The direction commands worked well. So did the horn, the solenoid (pen holder) and the bumper sensors but the two front lights would not come on. So at that stage the remaining tasks were to fix the lights and the bumper bar which was broken in two and twisted. I knew these issues were minor and that they were repairable but the problem was deciding on how these repairs were to be done. I'm sure it's a common dilemma when restoring an item and knowing certain parts are no longer available. Do you keep the item in its original state even if that means putting up with non working parts or do you replace the parts with reproductions, if available, or attempt to repair the items even if that means potentially destroying something in the process?



With the broken bumper bar I was considering replacing it with a newly constructed one made from MDF. MDF was the closest material I could think of which would be light enough (original bumper weighs just 128g), strong enough and easy to work with. I took the dimensions before attempting to restore the bumper in case I screwed it up. MDF would be my fall back in case I could not fix the original one. The bumper is made from a foam product that is set hard. The cross section looks like the honeycomb part of a Crunchie chocolate bar. I used a hairdryer to heat the material and bit by bit pushed the material back to how it was meant to be. Super glue was then used to join the parts together. Only time will tell if this is an adequate fix.



To investigate why the lights were not working I needed to disassemble the robot, not all the way but just enough to get to the lights. I used this opportunity to clean the robot and documented the printed circuit boards. The power was going to the lights so it was just an issue with the bulbs not working. I found the bulbs glued into the indicator light holders. This would help the bulbs from coming out due to vibrations but it becomes a maintenance nightmare. The only way I was able to get them out was by breaking the glass and using pliers to unscrew the remaining base. I damaged the light holders in the process. The light holders come in several sections and when they are all screwed together the broken section is not visible from the outside. I would rather replace the whole holder and I did attempt to contact the manufacturer but I'm yet to hear back from them. Incandescent light bulbs are also becoming difficult to source so I could have replaced them with LEDs but again I decided I wanted to be true to the original design. Since the UK still has a large doll house and model train market I was able to get the bulbs I needed by importing them.



A standard Input/Output card can be used to talk to the robot however it was nice having the Turtle Addressing Board so that I didn't have to go about working out all the connection cable wiring.



The connection cable is wired directly to the interface board. It was designed and built like this because the early Apple II models have the slot holes open at the top. It makes it a pain to use on the IIe and IIGS models because these have closed slot holes.

A quick video demonstration of the turtle can be found here https://docs.google.com/open?id=0B5PVarmqxaOnLVQxNVp1U2EwTE0.

I was going to complete this blog at this point but I thought how wonderful it would have been to have included the extended options that were available for the robot, like the Turtle Talk Board and/or the Electronic Compass. Obtaining information on these proved even more difficult. Sometimes Google just doesn't have all the answers but it does provide leads. I was able to do research the old fashioned way and that was to let my feet do the walking. I ended up at the State Library from which I was then able to access old magazine articles. From these articles, along with the LOGO software examples which I already had and a bit of re-engineering thrown in, I was able to piece together the schematics for both boards.



The electronic compass isn't really a compass. Not in the same sense that we would consider an electronic compass these days. It's just sixteen LEDs from which one is lit up based on a four bit number that is supplied to it by the computer. It's up to the computer and the programming language to keep track of the compass direction based on a starting location, usually just the initial power up location. I've created a functional equivalent schematic but it would be nice to find information to see how it was actually done.

The turtle talk board is based around the National's DT1050 Digitalker. This was one of several affordable speech chips from the early eighties. The other two big ones being the Texas Instruments' TMS-5100 which ended up in the "Speak and Spell" products and the Votrax's SC-01 which in an updated form ended up in the Sweet Micro Systems' Mockingboard cards. The Digitalker has the best sounding speech but at the cost of needing more storage then the other methods. However, only a modest amount more. From the top view of the PCB, partial schematics and LOGO software examples I was able to pull together the schematic for the board which I believe is pretty close to the original. I would love to find the bottom section of the PCB so I could verify my assumptions. If anyone can help out then please contact me. Otherwise I'll just have to build the card and debug it on the fly. Thanks to Jonathan I also have the standard ROM dumps SSR1 and SSR2 however I would love to get my hands on the extended ROM images SSR5 and SSR6. Maybe these will turn up one day.

Here is an attached file with schematics and pictures of each board, disk images, Tasman Turtle manuals, LOGO tutorials and more. Hopefully enough information to get any other Tasman Turtle restored to working order. https://docs.google.com/open?id=0B5PVarmqxaOnWXVlZlJFNU5Mem8

In the end, not only did I get to see a working Tasman Turtle but I got to restore it, program it and play with it. The perfect outcome.

4 comments:

Anonymous said...

Great read! We had similar LOGO robots in after school programs in Canada, and it was great to see one back on the road.

If that bumper breaks, consider EVA foam. It's light and sturdy, and easy to work with. MDF is actually very heavy for its volume. They use if for subwoofers for that reason. You might also consider acrylic- very stiff and light. EVA foam can be bought in craft stores, or at home improvement stores as interlocking floor mats.

Lukazi said...

Thanks for the tip. I'll certainly look into that.

Cheers,
Alex.

Chris Singley said...

I have a tasman turtle tot,never used, in the original plastic bags. all cables and disks included, in the original case. know anyone who would want it?

Lukazi said...

Hi Chris,
Send me a message to my email address lukazi@hotmail.com so I can reply.
Cheers,
Alex.