Thank you guys, your advice is a huge help to me, I'll start revising my drawings ASAP!
It is great learning this, and it is helping me understand things a lot better as I go (hopefully others too). Hopefully I can try to explain each part.
Do you intend 'basic' as 'least parts and as simple as possible' or 'minimal good implementation'?
It's a good question…and it comes down to keeping the concept a level well below what the Gertboard offers (which is an all you can eat buffet of goodness!). On the above balance points, it has to be sided on the 'least parts and as simple as possible' [add to that cheap as possible too] then if possible 'minimal good implementation'.
My thinking is, you may build a project using a R-Pi and develop it using the Gertboard, but it'll be nice to free up the Gertboard afterwards to develop your next project. Also, if you want to experiment with I/O without planning on doing anything too complicated.
For now, I'm thinking these circuits should be aimed at breadboard and stripboard designs, which keeps things low level and fully adaptable. This means, people can take the circuit designs, use additional suggested improvements (i.e to add 'minimal good implementation' aka buffer ICs) where they are happy to add the cost or understand enough to not need it. The idea is to create a guide for beginners, not to produce a product or board (although basic PCB designs could be made if required I guess – although I hope the circuits will be simple enough without).
- Circuits 1 [LED] and 2 [Motor Drive] -
The motor drive would need to have the transistor between the motor and gnd, as drawn it won't work and may damage the RPi.
– I would also use an opto-isolator to drive a MOSFET to protect the RPi from under/overvolt from motor start/stop. This also allows the motor to have a completely separate power supply at any (safe) voltage.
Oh yes, it would draw current from the base as well as collector, I suppose. As error404 also mentions, same will be best for the LED too.
- Circuit 3 [Switch] -
Minimal de-bounce or perhaps none at all (probably the easiest way is to test and try it out!), I agree to keep things simple the noise can be handled within the software. Will also ensure there are pull-ups.
- Circuit 4 [Analogue sensor to digital input] -
For most cases the simple circuit I think would be enough, perhaps we can create a more complex one later on using comparators (for specific applications). Perhaps most would find themselves better off using the Gertboard and it's ADC inputs for experimenting with, putting in software hysteresis (and any number of control methods they want to try).
- Buffering/Protection -
I think to resolve the buffer side of it, is to make it an optional addition to the circuit if required. The opto-isolating ICs make good sense, and to a beginner, very easy to explain their function, also they are something which once you have one you can reuse as you experiment.
Is the following suitable?
However, would using those, allow for the lower powered transistors to be dropped anyway i.e for LED driving? Perhaps it would simplify some of the circuits anyway (since it is just designs can have both options).
I'll probably get hold of a LaunchPad board anyway, since its such a low price, it is worth having to play around with and test these things on (although will compare it's specs).
Again, thanks for the help, and keep the advice coming, I know I am not the only person who has the WILL but not necessarily the RIGHT knowledge to do the projects we have in mind.