Anyway, before we delve into this latest project, I like to first give an update on interfacing the robotic arm with the internet. Everything had been going very smoothly with this project, all the code was working an I managed to get the Raspberry Pi 2 to output serial data when a button was clicked on the webpage. In fact in terms of a private webpage we were very close to the finished product, but alas it wasn't to be. The servo's on the robotic arm kept breaking. I replaced at least four servo's before I decided that it was costing me too much money to keep putting new ones in. They wouldn't last very long and even more expensive metal gear versions didn't cut the mustard.
So what went wrong? Well as a lot of makers say when they start explaining a project - "There are things I would do differently next time" - and this is very prominent when talking about Jerry the Robotic Arm. The servo's I chose to use were not up to the job of lifting the weight of the robotic arm, and this is down to the torque they could provide. All servo's have something called stall torque in their specification; this is the minimum amount of torque that the servo stalls at and stops moving even when you tell it to move. The closer you get to the stall torque the higher the amount of current required to move the servo; what's more this is more of an upwards curve than a linear increase. My servo's were on the edge of their stall torque, so they drew a lot of current and overheated. This causes the nylon teeth on the gears to strip away very easily and the servo would break. The metal gear servo's would just strip due to the force that was being applied to them, although they did last a bit longer than the nylon gear ones.
So what would I do next time? Well I would make the arm smaller for starters, this just makes everything easier as parts are lighter and less expensive. Thus less powerful servo's are needed to move the whole arm, again saving money! There is a chance that I could re-design some of Jerry's structural parts to take higher torque servo's and I may do this in the future. But for the time being at least this project is on hold! Hence why I am starting this different project! Now that we have got that rather sad news out of the way we can move onto brighter things and talk about the project that will be replacing it! Thinking caps at the ready, this ones a bit technical!
The Z80 Processor, building your own single board computer!
The Plan:
As with all slightly more complicated things, it's good to have a plan. So here's mine!
- Design a schematic for the base board, this will house the Processor, it's RAM (Random Access Memory) and ROM (Read only Memory) as well as the glue logic (The stuff that holds everything together, allowing the Processor to talk to other chips!) that is required to interface it with peripherals. (Complete)
- Order the parts required for the base board, wait excitedly for them to arrive, then build the base board!
- Test the Base Board by inputting code directly into the data bus (Explained Later) using simple switches!
- Do a little dance when it works.
- Design a schematic for an LCD display peripheral so that the Z80 can display text on a simple LCD display.
- Design a schematic so that the Z80 can take keyboard input.
- Build both boards and test.
- See where we go from there!
Part One - The schematic!
I thought I'd also do this one in a video, as it would be a lot of reading for you otherwise! So I'll let video Sam take over now!
Thanks for reading!
Sam