WIP & Refinements

Curently, now the Sensors have been updated following the feedback from Babylon 5, I’ve started working on one of the refinements to the emitter circuits to make them a little cheaper (less componants) before fully publishing everything.

It can be summarised as changing the way the signal sent to the IR emitter is generated.

The current circuits, PPG and in-development use an EXTERNAL signal modulation method – this is the easiest to code, but needs additional external componants.

In this it uses the PWNOUT command in picaxe basic to generate the 57.6kHz carrier signal on 1 pin, and the 1800hz “Hit” signal on a different pin. These two signals are then fed into an external AND gate made from transistors and then, (depending on power output desired) fed into a Mosfet to drive the emitter.

For the data signal, it replaced the hit signal output on the pin with the serial data output after 50 mS, using the Picaxe basic command to generate serial data via the software on any pin. Relatively simple and working fine now.

The refinement in development however takes advantage of some of the modules built into the PIC chip that is the core of the Picaxe to output a fully modulated signal on a single pin, without needing the components for the external AND gate – the payoff is it’s more difficult to code.

In a nutshell –

It tells the PWM module that generates the PWM  “carrier” and “hit” signals module to not output to the physical pins

Then tells the Data Signal Modulator to use 2 PWM module outputs above as the input.

Triggering the signal is a case of switching the ”hit” signal generation on or off depending.

For the data signal, it’s a case of telling the Data Signal Modulator to use the serial signal instead of the Hit signal

The part I’m currently working on is the switch between Hit signal and Serial data signal - I’ve got the serial data outputting on the Serial out pin. I need to get it switching off the physical pin output for the serial code and also changing the source for the 2^nd input to the data signal modulator. I’m hoping to have it done by the end of the weekend.

Overall though in the end it’ll be worth it, as while the external modulation is quite simple to code, it is a little more expensive components wise, and this is essentially a refinement to get the costs down