Saturday, 3 October 2015

5 Point Iris

A second mechanism for Vale LRP and another file that has been floating round the internet. This Iris is a neat piece of engineering that has been built by dozens of people. I rejigged it slightly to put some better gears around the outside but other than that it's the same. Instead of using nuts and bolts to hold it all together it is all made from wooden parts, each pivot point is made from a 6mm wooden dowel. (svg here)

Friday, 2 October 2015

Non Circular Planetary Gears

I needed to make a dohicky for Vale LRP and I wanted something quick and easy so I trawled the net and found these non circular gears of Thingiverse. A bit of steampunking later and I had something neat that would fit into the genre. I've included my files here which are a bit of a mess but at least they will open in inkscape now (svg here)

Thursday, 1 October 2015

Nottingham Theatre Royal in Cake

I recently helped Dawn from Dinkydoodle Designs create a cake for the 150 anniversary of the Nottingham Theatre Royal. The cake was presented to Prince Edward as part of the celebrations and he had the honour of cutting it. The cake was built in 2 halves and 5 floors, each floor had a baseboard (laser cut), built up with sponge cake and covered with chocolate ganache before the decoration and detailing went on. The floors were separated with cake frame to stop them squashing the sponge (now available from Lakeland plastics apparently). 

My involvement didn't stop with base boards though, once the basic shape was carved out I was called back in to wire the cake with lights. The front porch is lit, the chandelier and auditorium were illuminated with LED strips and the stage area was lit with a WS2811 strip and an arduino nano changed the colours every 10 seconds to give a sense of movement.

Here is a little video tour of the cake once it was opened.

The cake was built in 2 halves so that the internals were hidden until the cake was slid apart allowing people to see all the extra detail on the inside of the cake. Dawn has more photos of the cake on her facebook page here.


Wednesday, 30 September 2015

Project #8 - Catapult Range Finished

This project was remade from the first prototype and it was ready for my Cambridge workshop on the 13th, it's just taken me an additional 2 weeks to actually write about it. The principle is very much the same, I have fully enclosed the range with perspex to make it better at keeping the ammo in the range but also added a few other features.

This time I ran the strings over the top of the board. It was easier than worrying about routing the string past the braces on the underside of the board but also it allows the kids to see a greater connection between the levers and the targets. In Cambridge nobody asked what the levers were for so I guess it served it's purpose. The levers are now vertically mounted so that gravity pulls them down again, this makes the string slack while resting and the targets more likely to fall over. The targets themselves are now bolted to the base board rather than glued, this makes them nigh on impossible to break off with catapult shot. 

While in operation balls were getting stuck behind parts and we were having to remove the framework to get a hand in there and free parts up, I removed most of the natural ledges to limit this from happening and now balls only get stuck behind the targets. I made the rear third of the perspex screen an access panel. It can be lifted high enough to get a hand under and the balls can be moved as appropriate.

When not in use the catapult range is largely empty space, there is a big volume that could be minimised for transport and storage. The rear wall and lid can be removed, the two perspex side walls are hinged so they can be folded into the range. All the targets go flat so they aren't in the way. The whole range can be stored vertically and carried under one arm which should make it easy to get in and out of maker faires. Come and try it for yourself at the upcoming Derby Mini Maker Faire

Monday, 28 September 2015

Cake Building Layers

This is another large cake framework for Dinky Doodle cakes, This is taken from a floor plan of the theatre royal in Nottingham, each layer is a different floor of the building and it will be used to create the whole building from cake. The top layer is a roof because inside the cake the auditorium will be recreated with lights and a stage.

This is Dawns model of the cake that she cut by hand to show me what we are doing.

Sunday, 27 September 2015

Fail and Fail Fast - Leetro Controller vs PAD03

Not every project can be a success and there is a popular mantra that you should fail and fail fast. You learn from failures and the sooner you get them out the way the sooner you can move on to the right ways. I don't have a lot of failures, I have a lot of projects that get put on hold until I know how to progress them, some of them are on indefinite hold at the moment. Tonight's project has been on the cards for a few months but it failed and relatively quickly so I thought I would write about it as I'm no longer working on it.

A lot of Chinese laser cutters come supplied with the Leetro controller MPC6515 or MPC6535, both use the PAD03 display panel to communicate information to the user. The system has a fair few quirks but the one that really bugs me involves the Z axis adjustment. You press 'Z' to move into the height adjustment mode but pressing 'Esc' does not get you out of the mode, you have to press 'Z' again. The idea is simple though break into the loop between the panel and the controller, catch the 'Esc' key as it is pressed and turn it into a 'Z' key press so that the controller leaves Z mode.

We know from the manual that the panel communicates via RS485 and at 9600 Baud using a Modbus protocol. There are a few modbus interpreters for arduino so I bought 2 level shifters to convert from RS485 levels to TTL levels. I chose the Arduino Mega because it has 4 hardware serial ports. The test set up has the controller connected to the Arduino on serial 1 and the panel connected to serial 2. The software just relays bytes from one serial port to the other but it also copies those bytes out to the PC so the data can be seen on a screen with a serial terminal. I had hoped to catch the text data being sent to and from the panel.

With everything connected and the data relayed back to the PC I turned the system on. Data was successfully passed through the Arduino to and from the controller, the system functioned normally despite the Arduino in the loop. Pressing buttons on the panel created additional data on the screen so it should have been easy to spot the key presses. I switched the panel into z mode and started pushing buttons. Only the 'Up' and 'Down' buttons were actually passed back to the controller, none of the other buttons were.

The conclusion is fairly simple. The panel understands that it is part of a laser cutter system, it's not just a dumb terminal reflecting information from the controller. It is the panel that switches the display into 'Z' mode and it is the panel that prevents it from coming out again. The project was a bust but I learned more about the system in the process and that is useful in itself.

New Catapult instructions

The catapult has been around for a long time at various scales and versions, I recently sold a dozen to someone for a wedding and realised that the instructions were lacking a little. I redrew them attempting for a new words Ikea style, they're not as clear as they could be but I think they're acceptable and I'm pleased with the artwork anyway. (pdf here)